chore: Release

Improve initialization in workspace

.github/workflows/rust.yml

@@ -23,7 +23,7 @@ jobs:
         with:
           globs: "exercises/**/*.md"
       - name: Run cargo fmt
-        run: cargo fmt --all -- --check
+        run: cargo fmt --all --check
   test:
     runs-on: ${{ matrix.os }}
     strategy:
@@ -33,7 +33,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: swatinem/rust-cache@v2
       - name: Run cargo test
-        run: cargo test
+        run: cargo test --workspace
   dev-check:
     runs-on: ubuntu-latest
     steps:

CHANGELOG.md

@@ -1,3 +1,40 @@
+<a name="6.2.0"></a>
+
+## 6.2.0 (2024-08-09)
+
+### Added
+
+- Show a message before checking and running an exercise. This gives the user instant feedback and avoids confusion if the checks take too long.
+- Show a helpful error message when trying to install Rustlings with a Rust version lower than the minimum one that Rustlings supports.
+- Add a `README.md` file to the `solutions/` directory.
+- Allow initializing Rustlings in a Cargo workspace.
+- `dev check`: Check that all solutions are formatted with `rustfmt`.
+
+### Changed
+
+- Remove the state file and the solutions directory from the generated `.gitignore` file.
+- Run the final check of all exercises in parallel.
+- Small exercise improvements.
+
+<a name="6.1.0"></a>
+
+## 6.1.0 (2024-07-10)
+
+#### Added
+
+- `dev check`: Check that all exercises (including third-party ones) include at least one `TODO` comment.
+- `dev check`: Check that all exercises actually fail to run (not already solved).
+
+#### Changed
+
+- Make enum variants more consistent between enum exercises.
+- `iterators3`: Teach about the possible case of integer overflow during division.
+
+#### Fixed
+
+- Exit with a helpful error message on missing/unsupported terminal/TTY.
+- Mark the last exercise as done.
+
 <a name="6.0.1"></a>
 
 ## 6.0.1 (2024-07-04)
@@ -64,7 +101,7 @@ This should avoid issues related to the language server or to running exercises,
 Clippy lints are now shown on all exercises, not only the Clippy exercises 📎
 Make Clippy your friend from early on 🥰
 
-### Third party exercises
+### Third-party exercises
 
 Rustlings now supports third-party exercises!
 

Cargo.lock

@@ -14,15 +14,6 @@ dependencies = [
  "zerocopy",
 ]
 
-[[package]]
-name = "aho-corasick"
-version = "1.1.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8e60d3430d3a69478ad0993f19238d2df97c507009a52b3c10addcd7f6bcb916"
-dependencies = [
- "memchr",
-]
-
 [[package]]
 name = "allocator-api2"
 version = "0.2.18"
@@ -31,9 +22,9 @@ checksum = "5c6cb57a04249c6480766f7f7cef5467412af1490f8d1e243141daddada3264f"
 
 [[package]]
 name = "anstream"
-version = "0.6.14"
+version = "0.6.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "418c75fa768af9c03be99d17643f93f79bbba589895012a80e3452a19ddda15b"
+checksum = "64e15c1ab1f89faffbf04a634d5e1962e9074f2741eef6d97f3c4e322426d526"
 dependencies = [
  "anstyle",
  "anstyle-parse",
@@ -46,33 +37,33 @@ dependencies = [
 
 [[package]]
 name = "anstyle"
-version = "1.0.7"
+version = "1.0.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "038dfcf04a5feb68e9c60b21c9625a54c2c0616e79b72b0fd87075a056ae1d1b"
+checksum = "1bec1de6f59aedf83baf9ff929c98f2ad654b97c9510f4e70cf6f661d49fd5b1"
 
 [[package]]
 name = "anstyle-parse"
-version = "0.2.4"
+version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c03a11a9034d92058ceb6ee011ce58af4a9bf61491aa7e1e59ecd24bd40d22d4"
+checksum = "eb47de1e80c2b463c735db5b217a0ddc39d612e7ac9e2e96a5aed1f57616c1cb"
 dependencies = [
  "utf8parse",
 ]
 
 [[package]]
 name = "anstyle-query"
-version = "1.1.0"
+version = "1.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ad186efb764318d35165f1758e7dcef3b10628e26d41a44bc5550652e6804391"
+checksum = "6d36fc52c7f6c869915e99412912f22093507da8d9e942ceaf66fe4b7c14422a"
 dependencies = [
  "windows-sys 0.52.0",
 ]
 
 [[package]]
 name = "anstyle-wincon"
-version = "3.0.3"
+version = "3.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "61a38449feb7068f52bb06c12759005cf459ee52bb4adc1d5a7c4322d716fb19"
+checksum = "5bf74e1b6e971609db8ca7a9ce79fd5768ab6ae46441c572e46cf596f59e57f8"
 dependencies = [
  "anstyle",
  "windows-sys 0.52.0",
@@ -84,21 +75,6 @@ version = "1.0.86"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b3d1d046238990b9cf5bcde22a3fb3584ee5cf65fb2765f454ed428c7a0063da"
 
-[[package]]
-name = "assert_cmd"
-version = "2.0.14"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ed72493ac66d5804837f480ab3766c72bdfab91a65e565fc54fa9e42db0073a8"
-dependencies = [
- "anstyle",
- "bstr",
- "doc-comment",
- "predicates",
- "predicates-core",
- "predicates-tree",
- "wait-timeout",
-]
-
 [[package]]
 name = "autocfg"
 version = "1.3.0"
@@ -117,17 +93,6 @@ version = "2.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b048fb63fd8b5923fc5aa7b340d8e156aec7ec02f0c78fa8a6ddc2613f6f71de"
 
-[[package]]
-name = "bstr"
-version = "1.9.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "05efc5cfd9110c8416e471df0e96702d58690178e206e61b7173706673c93706"
-dependencies = [
- "memchr",
- "regex-automata",
- "serde",
-]
-
 [[package]]
 name = "cassowary"
 version = "0.3.0"
@@ -151,9 +116,9 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
 [[package]]
 name = "clap"
-version = "4.5.8"
+version = "4.5.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "84b3edb18336f4df585bc9aa31dd99c036dfa5dc5e9a2939a722a188f3a8970d"
+checksum = "c937d4061031a6d0c8da4b9a4f98a172fc2976dfb1c19213a9cf7d0d3c837e36"
 dependencies = [
  "clap_builder",
  "clap_derive",
@@ -161,9 +126,9 @@ dependencies = [
 
 [[package]]
 name = "clap_builder"
-version = "4.5.8"
+version = "4.5.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c1c09dd5ada6c6c78075d6fd0da3f90d8080651e2d6cc8eb2f1aaa4034ced708"
+checksum = "85379ba512b21a328adf887e85f7742d12e96eb31f3ef077df4ffc26b506ffed"
 dependencies = [
  "anstream",
  "anstyle",
@@ -173,9 +138,9 @@ dependencies = [
 
 [[package]]
 name = "clap_derive"
-version = "4.5.8"
+version = "4.5.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2bac35c6dafb060fd4d275d9a4ffae97917c13a6327903a8be2153cd964f7085"
+checksum = "501d359d5f3dcaf6ecdeee48833ae73ec6e42723a1e52419c79abf9507eec0a0"
 dependencies = [
  "heck",
  "proc-macro2",
@@ -185,25 +150,26 @@ dependencies = [
 
 [[package]]
 name = "clap_lex"
-version = "0.7.1"
+version = "0.7.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4b82cf0babdbd58558212896d1a4272303a57bdb245c2bf1147185fb45640e70"
+checksum = "1462739cb27611015575c0c11df5df7601141071f07518d56fcc1be504cbec97"
 
 [[package]]
 name = "colorchoice"
-version = "1.0.1"
+version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0b6a852b24ab71dffc585bcb46eaf7959d175cb865a7152e35b348d1b2960422"
+checksum = "d3fd119d74b830634cea2a0f58bbd0d54540518a14397557951e79340abc28c0"
 
 [[package]]
 name = "compact_str"
-version = "0.7.1"
+version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f86b9c4c00838774a6d902ef931eff7470720c51d90c2e32cfe15dc304737b3f"
+checksum = "6050c3a16ddab2e412160b31f2c871015704239bca62f72f6e5f0be631d3f644"
 dependencies = [
  "castaway",
  "cfg-if",
  "itoa",
+ "rustversion",
  "ryu",
  "static_assertions",
 ]
@@ -225,15 +191,15 @@ checksum = "22ec99545bb0ed0ea7bb9b8e1e9122ea386ff8a48c0922e43f36d45ab09e0e80"
 
 [[package]]
 name = "crossterm"
-version = "0.27.0"
+version = "0.28.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f476fe445d41c9e991fd07515a6f463074b782242ccf4a5b7b1d1012e70824df"
+checksum = "829d955a0bb380ef178a640b91779e3987da38c9aea133b20614cfed8cdea9c6"
 dependencies = [
  "bitflags 2.6.0",
  "crossterm_winapi",
- "libc",
- "mio",
+ "mio 1.0.1",
  "parking_lot",
+ "rustix",
  "signal-hook",
  "signal-hook-mio",
  "winapi",
@@ -248,18 +214,6 @@ dependencies = [
  "winapi",
 ]
 
-[[package]]
-name = "difflib"
-version = "0.4.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6184e33543162437515c2e2b48714794e37845ec9851711914eec9d308f6ebe8"
-
-[[package]]
-name = "doc-comment"
-version = "0.3.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fea41bba32d969b513997752735605054bc0dfa92b4c56bf1189f2e174be7a10"
-
 [[package]]
 name = "either"
 version = "1.13.0"
@@ -272,6 +226,22 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5443807d6dff69373d433ab9ef5378ad8df50ca6298caf15de6e52e24aaf54d5"
 
+[[package]]
+name = "errno"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "534c5cf6194dfab3db3242765c03bbe257cf92f22b38f6bc0c58d59108a820ba"
+dependencies = [
+ "libc",
+ "windows-sys 0.52.0",
+]
+
+[[package]]
+name = "fastrand"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9fc0510504f03c51ada170672ac806f1f105a88aa97a5281117e1ddc3368e51a"
+
 [[package]]
 name = "filetime"
 version = "0.2.23"
@@ -284,15 +254,6 @@ dependencies = [
  "windows-sys 0.52.0",
 ]
 
-[[package]]
-name = "float-cmp"
-version = "0.9.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "98de4bbd547a563b716d8dfa9aad1cb19bfab00f4fa09a6a4ed21dbcf44ce9c4"
-dependencies = [
- "num-traits",
-]
-
 [[package]]
 name = "fsevent-sys"
 version = "4.1.0"
@@ -319,10 +280,16 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
 
 [[package]]
-name = "indexmap"
-version = "2.2.6"
+name = "hermit-abi"
+version = "0.3.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "168fb715dda47215e360912c096649d23d58bf392ac62f73919e831745e40f26"
+checksum = "d231dfb89cfffdbc30e7fc41579ed6066ad03abda9e567ccafae602b97ec5024"
+
+[[package]]
+name = "indexmap"
+version = "2.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "de3fc2e30ba82dd1b3911c8de1ffc143c74a914a14e99514d7637e3099df5ea0"
 dependencies = [
  "equivalent",
  "hashbrown",
@@ -349,19 +316,20 @@ dependencies = [
 ]
 
 [[package]]
-name = "is_terminal_polyfill"
-version = "1.70.0"
+name = "instability"
+version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f8478577c03552c21db0e2724ffb8986a5ce7af88107e6be5d2ee6e158c12800"
+checksum = "b23a0c8dfe501baac4adf6ebbfa6eddf8f0c07f56b058cc1288017e32397846c"
+dependencies = [
+ "quote",
+ "syn",
+]
 
 [[package]]
-name = "itertools"
-version = "0.12.1"
+name = "is_terminal_polyfill"
+version = "1.70.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ba291022dbbd398a455acf126c1e341954079855bc60dfdda641363bd6922569"
-dependencies = [
- "either",
-]
+checksum = "7943c866cc5cd64cbc25b2e01621d07fa8eb2a1a23160ee81ce38704e97b8ecf"
 
 [[package]]
 name = "itertools"
@@ -404,6 +372,12 @@ version = "0.2.155"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "97b3888a4aecf77e811145cadf6eef5901f4782c53886191b2f693f24761847c"
 
+[[package]]
+name = "linux-raw-sys"
+version = "0.4.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "78b3ae25bc7c8c38cec158d1f2757ee79e9b3740fbc7ccf0e59e4b08d793fa89"
+
 [[package]]
 name = "lock_api"
 version = "0.4.12"
@@ -422,9 +396,9 @@ checksum = "a7a70ba024b9dc04c27ea2f0c0548feb474ec5c54bba33a7f72f873a39d07b24"
 
 [[package]]
 name = "lru"
-version = "0.12.3"
+version = "0.12.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d3262e75e648fce39813cb56ac41f3c3e3f65217ebf3844d818d1f9398cfb0dc"
+checksum = "37ee39891760e7d94734f6f63fedc29a2e4a152f836120753a72503f09fcf904"
 dependencies = [
  "hashbrown",
 ]
@@ -448,10 +422,17 @@ dependencies = [
 ]
 
 [[package]]
-name = "normalize-line-endings"
-version = "0.3.0"
+name = "mio"
+version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "61807f77802ff30975e01f4f071c8ba10c022052f98b3294119f3e615d13e5be"
+checksum = "4569e456d394deccd22ce1c1913e6ea0e54519f577285001215d33557431afe4"
+dependencies = [
+ "hermit-abi",
+ "libc",
+ "log",
+ "wasi",
+ "windows-sys 0.52.0",
+]
 
 [[package]]
 name = "notify"
@@ -467,7 +448,7 @@ dependencies = [
  "kqueue",
  "libc",
  "log",
- "mio",
+ "mio 0.8.11",
  "walkdir",
  "windows-sys 0.48.0",
 ]
@@ -482,15 +463,6 @@ dependencies = [
  "notify",
 ]
 
-[[package]]
-name = "num-traits"
-version = "0.2.19"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "071dfc062690e90b734c0b2273ce72ad0ffa95f0c74596bc250dcfd960262841"
-dependencies = [
- "autocfg",
-]
-
 [[package]]
 name = "once_cell"
 version = "1.19.0"
@@ -499,12 +471,12 @@ checksum = "3fdb12b2476b595f9358c5161aa467c2438859caa136dec86c26fdd2efe17b92"
 
 [[package]]
 name = "os_pipe"
-version = "1.2.0"
+version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "29d73ba8daf8fac13b0501d1abeddcfe21ba7401ada61a819144b6c2a4f32209"
+checksum = "5ffd2b0a5634335b135d5728d84c5e0fd726954b87111f7506a61c502280d982"
 dependencies = [
  "libc",
- "windows-sys 0.52.0",
+ "windows-sys 0.59.0",
 ]
 
 [[package]]
@@ -525,7 +497,7 @@ checksum = "1e401f977ab385c9e4e3ab30627d6f26d00e2c73eef317493c4ec6d468726cf8"
 dependencies = [
  "cfg-if",
  "libc",
- "redox_syscall 0.5.2",
+ "redox_syscall 0.5.3",
  "smallvec",
  "windows-targets 0.52.6",
 ]
@@ -536,36 +508,6 @@ version = "1.0.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "57c0d7b74b563b49d38dae00a0c37d4d6de9b432382b2892f0574ddcae73fd0a"
 
-[[package]]
-name = "predicates"
-version = "3.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "68b87bfd4605926cdfefc1c3b5f8fe560e3feca9d5552cf68c466d3d8236c7e8"
-dependencies = [
- "anstyle",
- "difflib",
- "float-cmp",
- "normalize-line-endings",
- "predicates-core",
- "regex",
-]
-
-[[package]]
-name = "predicates-core"
-version = "1.0.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b794032607612e7abeb4db69adb4e33590fa6cf1149e95fd7cb00e634b92f174"
-
-[[package]]
-name = "predicates-tree"
-version = "1.0.9"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "368ba315fb8c5052ab692e68a0eefec6ec57b23a36959c14496f0b0df2c0cecf"
-dependencies = [
- "predicates-core",
- "termtree",
-]
-
 [[package]]
 name = "proc-macro2"
 version = "1.0.86"
@@ -586,18 +528,18 @@ dependencies = [
 
 [[package]]
 name = "ratatui"
-version = "0.27.0"
+version = "0.28.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d16546c5b5962abf8ce6e2881e722b4e0ae3b6f1a08a26ae3573c55853ca68d3"
+checksum = "5ba6a365afbe5615999275bea2446b970b10a41102500e27ce7678d50d978303"
 dependencies = [
  "bitflags 2.6.0",
  "cassowary",
  "compact_str",
  "crossterm",
- "itertools 0.13.0",
+ "instability",
+ "itertools",
  "lru",
  "paste",
- "stability",
  "strum",
  "strum_macros",
  "unicode-segmentation",
@@ -616,64 +558,46 @@ dependencies = [
 
 [[package]]
 name = "redox_syscall"
-version = "0.5.2"
+version = "0.5.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c82cf8cff14456045f55ec4241383baeff27af886adb72ffb2162f99911de0fd"
+checksum = "2a908a6e00f1fdd0dfd9c0eb08ce85126f6d8bbda50017e74bc4a4b7d4a926a4"
 dependencies = [
  "bitflags 2.6.0",
 ]
 
 [[package]]
-name = "regex"
-version = "1.10.5"
+name = "rustix"
+version = "0.38.34"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b91213439dad192326a0d7c6ee3955910425f441d7038e0d6933b0aec5c4517f"
+checksum = "70dc5ec042f7a43c4a73241207cecc9873a06d45debb38b329f8541d85c2730f"
 dependencies = [
- "aho-corasick",
- "memchr",
- "regex-automata",
- "regex-syntax",
+ "bitflags 2.6.0",
+ "errno",
+ "libc",
+ "linux-raw-sys",
+ "windows-sys 0.52.0",
 ]
 
-[[package]]
-name = "regex-automata"
-version = "0.4.7"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "38caf58cc5ef2fed281f89292ef23f6365465ed9a41b7a7754eb4e26496c92df"
-dependencies = [
- "aho-corasick",
- "memchr",
- "regex-syntax",
-]
-
-[[package]]
-name = "regex-syntax"
-version = "0.8.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7a66a03ae7c801facd77a29370b4faec201768915ac14a721ba36f20bc9c209b"
-
 [[package]]
 name = "rustlings"
-version = "6.0.1"
+version = "6.2.0"
 dependencies = [
+ "ahash",
  "anyhow",
- "assert_cmd",
  "clap",
- "crossterm",
- "hashbrown",
  "notify-debouncer-mini",
  "os_pipe",
- "predicates",
  "ratatui",
  "rustlings-macros",
  "serde",
  "serde_json",
+ "tempfile",
  "toml_edit",
 ]
 
 [[package]]
 name = "rustlings-macros"
-version = "6.0.1"
+version = "6.2.0"
 dependencies = [
  "quote",
  "serde",
@@ -709,18 +633,18 @@ checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
 
 [[package]]
 name = "serde"
-version = "1.0.203"
+version = "1.0.205"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7253ab4de971e72fb7be983802300c30b5a7f0c2e56fab8abfc6a214307c0094"
+checksum = "e33aedb1a7135da52b7c21791455563facbbcc43d0f0f66165b42c21b3dfb150"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.203"
+version = "1.0.205"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "500cbc0ebeb6f46627f50f3f5811ccf6bf00643be300b4c3eabc0ef55dc5b5ba"
+checksum = "692d6f5ac90220161d6774db30c662202721e64aed9058d2c394f451261420c1"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -729,20 +653,21 @@ dependencies = [
 
 [[package]]
 name = "serde_json"
-version = "1.0.120"
+version = "1.0.122"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4e0d21c9a8cae1235ad58a00c11cb40d4b1e5c784f1ef2c537876ed6ffd8b7c5"
+checksum = "784b6203951c57ff748476b126ccb5e8e2959a5c19e5c617ab1956be3dbc68da"
 dependencies = [
  "itoa",
+ "memchr",
  "ryu",
  "serde",
 ]
 
 [[package]]
 name = "serde_spanned"
-version = "0.6.6"
+version = "0.6.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "79e674e01f999af37c49f70a6ede167a8a60b2503e56c5599532a65baa5969a0"
+checksum = "eb5b1b31579f3811bf615c144393417496f152e12ac8b7663bf664f4a815306d"
 dependencies = [
  "serde",
 ]
@@ -759,12 +684,12 @@ dependencies = [
 
 [[package]]
 name = "signal-hook-mio"
-version = "0.2.3"
+version = "0.2.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "29ad2e15f37ec9a6cc544097b78a1ec90001e9f71b81338ca39f430adaca99af"
+checksum = "34db1a06d485c9142248b7a054f034b349b212551f3dfd19c94d45a754a217cd"
 dependencies = [
  "libc",
- "mio",
+ "mio 1.0.1",
  "signal-hook",
 ]
 
@@ -783,16 +708,6 @@ version = "1.13.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3c5e1a9a646d36c3599cd173a41282daf47c44583ad367b8e6837255952e5c67"
 
-[[package]]
-name = "stability"
-version = "0.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2ff9eaf853dec4c8802325d8b6d3dffa86cc707fd7a1a4cdbf416e13b061787a"
-dependencies = [
- "quote",
- "syn",
-]
-
 [[package]]
 name = "static_assertions"
 version = "1.1.0"
@@ -829,9 +744,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "2.0.68"
+version = "2.0.72"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "901fa70d88b9d6c98022e23b4136f9f3e54e4662c3bc1bd1d84a42a9a0f0c1e9"
+checksum = "dc4b9b9bf2add8093d3f2c0204471e951b2285580335de42f9d2534f3ae7a8af"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -839,25 +754,32 @@ dependencies = [
 ]
 
 [[package]]
-name = "termtree"
-version = "0.4.1"
+name = "tempfile"
+version = "3.12.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3369f5ac52d5eb6ab48c6b4ffdc8efbcad6b89c765749064ba298f2c68a16a76"
+checksum = "04cbcdd0c794ebb0d4cf35e88edd2f7d2c4c3e9a5a6dab322839b321c6a87a64"
+dependencies = [
+ "cfg-if",
+ "fastrand",
+ "once_cell",
+ "rustix",
+ "windows-sys 0.59.0",
+]
 
 [[package]]
 name = "toml_datetime"
-version = "0.6.6"
+version = "0.6.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4badfd56924ae69bcc9039335b2e017639ce3f9b001c393c1b2d1ef846ce2cbf"
+checksum = "0dd7358ecb8fc2f8d014bf86f6f638ce72ba252a2c3a2572f2a795f1d23efb41"
 dependencies = [
  "serde",
 ]
 
 [[package]]
 name = "toml_edit"
-version = "0.22.14"
+version = "0.22.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f21c7aaf97f1bd9ca9d4f9e73b0a6c74bd5afef56f2bc931943a6e1c37e04e38"
+checksum = "583c44c02ad26b0c3f3066fe629275e50627026c51ac2e595cca4c230ce1ce1d"
 dependencies = [
  "indexmap",
  "serde",
@@ -880,11 +802,12 @@ checksum = "d4c87d22b6e3f4a18d4d40ef354e97c90fcb14dd91d7dc0aa9d8a1172ebf7202"
 
 [[package]]
 name = "unicode-truncate"
-version = "1.0.0"
+version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5a5fbabedabe362c618c714dbefda9927b5afc8e2a8102f47f081089a9019226"
+checksum = "b3644627a5af5fa321c95b9b235a72fd24cd29c648c2c379431e6628655627bf"
 dependencies = [
- "itertools 0.12.1",
+ "itertools",
+ "unicode-segmentation",
  "unicode-width",
 ]
 
@@ -902,18 +825,9 @@ checksum = "06abde3611657adf66d383f00b093d7faecc7fa57071cce2578660c9f1010821"
 
 [[package]]
 name = "version_check"
-version = "0.9.4"
+version = "0.9.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
-
-[[package]]
-name = "wait-timeout"
-version = "0.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9f200f5b12eb75f8c1ed65abd4b2db8a6e1b138a20de009dacee265a2498f3f6"
-dependencies = [
- "libc",
-]
+checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
 
 [[package]]
 name = "walkdir"
@@ -949,11 +863,11 @@ checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 
 [[package]]
 name = "winapi-util"
-version = "0.1.8"
+version = "0.1.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4d4cc384e1e73b93bafa6fb4f1df8c41695c8a91cf9c4c64358067d15a7b6c6b"
+checksum = "cf221c93e13a30d793f7645a0e7762c55d169dbb0a49671918a2319d289b10bb"
 dependencies = [
- "windows-sys 0.52.0",
+ "windows-sys 0.59.0",
 ]
 
 [[package]]
@@ -980,6 +894,15 @@ dependencies = [
  "windows-targets 0.52.6",
 ]
 
+[[package]]
+name = "windows-sys"
+version = "0.59.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e38bc4d79ed67fd075bcc251a1c39b32a1776bbe92e5bef1f0bf1f8c531853b"
+dependencies = [
+ "windows-targets 0.52.6",
+]
+
 [[package]]
 name = "windows-targets"
 version = "0.48.5"
@@ -1103,9 +1026,9 @@ checksum = "589f6da84c646204747d1270a2a5661ea66ed1cced2631d546fdfb155959f9ec"
 
 [[package]]
 name = "winnow"
-version = "0.6.13"
+version = "0.6.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "59b5e5f6c299a3c7890b876a2a587f3115162487e704907d9b6cd29473052ba1"
+checksum = "68a9bda4691f099d435ad181000724da8e5899daa10713c2d432552b9ccd3a6f"
 dependencies = [
  "memchr",
 ]

Cargo.toml

@@ -1,27 +1,26 @@
 [workspace]
 resolver = "2"
 exclude = [
-  "tests/fixture/failure",
-  "tests/fixture/state",
-  "tests/fixture/success",
+  "tests/test_exercises",
   "dev",
 ]
 
 [workspace.package]
-version = "6.0.1"
+version = "6.2.0"
 authors = [
-  "Liv <mokou@fastmail.com>",
-  "Mo Bitar <mo8it@proton.me>",
+  "Mo Bitar <mo8it@proton.me>", # https://github.com/mo8it
+  "Liv <mokou@fastmail.com>", # https://github.com/shadows-withal
   # Alumni
-  "Carol (Nichols || Goulding) <carol.nichols@gmail.com>",
+  "Carol (Nichols || Goulding) <carol.nichols@gmail.com>", # https://github.com/carols10cents
 ]
 repository = "https://github.com/rust-lang/rustlings"
 license = "MIT"
-edition = "2021"
+edition = "2021" # On Update: Update the edition of the `rustfmt` command that checks the solutions.
+rust-version = "1.80"
 
 [workspace.dependencies]
-serde = { version = "1.0.203", features = ["derive"] }
-toml_edit = { version = "0.22.14", default-features = false, features = ["parse", "serde"] }
+serde = { version = "1.0.205", features = ["derive"] }
+toml_edit = { version = "0.22.20", default-features = false, features = ["parse", "serde"] }
 
 [package]
 name = "rustlings"
@@ -31,6 +30,7 @@ authors.workspace = true
 repository.workspace = true
 license.workspace = true
 edition.workspace = true
+rust-version.workspace = true
 keywords = [
   "exercise",
   "learning",
@@ -46,21 +46,19 @@ include = [
 ]
 
 [dependencies]
+ahash = { version = "0.8.11", default-features = false }
 anyhow = "1.0.86"
-clap = { version = "4.5.8", features = ["derive"] }
-crossterm = "0.27.0"
-hashbrown = "0.14.5"
+clap = { version = "4.5.14", features = ["derive"] }
 notify-debouncer-mini = { version = "0.4.1", default-features = false }
-os_pipe = "1.2.0"
-ratatui = { version = "0.27.0", default-features = false, features = ["crossterm"] }
-rustlings-macros = { path = "rustlings-macros", version = "=6.0.1" }
-serde_json = "1.0.120"
+os_pipe = "1.2.1"
+ratatui = { version = "0.28.0", default-features = false, features = ["crossterm"] }
+rustlings-macros = { path = "rustlings-macros", version = "=6.2.0" }
+serde_json = "1.0.122"
 serde.workspace = true
 toml_edit.workspace = true
 
 [dev-dependencies]
-assert_cmd = "2.0.14"
-predicates = "3.1.0"
+tempfile = "3.12.0"
 
 [profile.release]
 panic = "abort"
@@ -70,3 +68,7 @@ panic = "abort"
 
 [package.metadata.release]
 pre-release-hook = ["./release-hook.sh"]
+
+# TODO: Remove after the following fix is released: https://github.com/rust-lang/rust-clippy/pull/13102
+[lints.clippy]
+needless_option_as_deref = "allow"

README.md

@@ -17,9 +17,9 @@ It contains code examples and exercises similar to Rustlings, but online.
 
 ### Installing Rust
 
-Before installing Rustlings, you need to have _Rust installed_.
+Before installing Rustlings, you need to have the **latest version of Rust** installed.
 Visit [www.rust-lang.org/tools/install](https://www.rust-lang.org/tools/install) for further instructions on installing Rust.
-This'll also install _Cargo_, Rust's package/project manager.
+This will also install _Cargo_, Rust's package/project manager.
 
 > 🐧 If you're on Linux, make sure you've installed `gcc` (for a linker).
 >
@@ -53,6 +53,21 @@ After installing Rustlings, run the following command to initialize the `rustlin
 rustlings init
 ```
 
+<details>
+<summary><strong>If the command <code>rustlings</code> can't be found…</strong> (<em>click to expand</em>)</summary>
+
+You are probably using Linux and installed Rust using your package manager.
+
+Cargo installs binaries to the directory `~/.cargo/bin`.
+Sadly, package managers often don't add `~/.cargo/bin` to your `PATH` environment variable.
+
+The solution is to …
+
+- either add `~/.cargo/bin` manually to `PATH`
+- or to uninstall Rust from the package manager and install it using the official way with `rustup`: https://www.rust-lang.org/tools/install
+
+</details>
+
 Now, go into the newly initialized directory and launch Rustlings for further instructions on getting started with the exercises:
 
 ```bash
@@ -73,8 +88,6 @@ While working with Rustlings, please use a modern terminal for the best user exp
 The default terminal on Linux and Mac should be sufficient.
 On Windows, we recommend the [Windows Terminal](https://aka.ms/terminal).
 
-If you use VS Code, the builtin terminal should also be fine.
-
 ## Doing exercises
 
 The exercises are sorted by topic and can be found in the subdirectory `exercises/<topic>`.
@@ -124,7 +137,7 @@ Continue practicing your Rust skills by building your own projects, contributing
 
 Do you want to create your own set of Rustlings exercises to focus on some specific topic?
 Or do you want to translate the original Rustlings exercises?
-Then follow the link to the guide about [third-party exercises](THIRD_PARTY_EXERCISES.md)!
+Then follow the link to the guide about [third-party exercises](https://github.com/rust-lang/rustlings/blob/main/THIRD_PARTY_EXERCISES.md)!
 
 ## Uninstalling Rustlings
 

THIRD_PARTY_EXERCISES.md

@@ -1,7 +1,7 @@
 # Third-Party Exercises
 
 The support of Rustlings for third-party exercises allows you to create your own set of Rustlings exercises to focus on some specific topic.
-You could also offer a translatation of the original Rustlings exercises as third-party exercises.
+You could also offer a translation of the original Rustlings exercises as third-party exercises.
 
 ## Getting started
 

dev/Cargo.toml

@@ -195,3 +195,9 @@ name = "exercises"
 edition = "2021"
 # Don't publish the exercises on crates.io!
 publish = false
+
+[profile.release]
+panic = "abort"
+
+[profile.dev]
+panic = "abort"

dev/rustlings-repo.txt

@@ -1 +1 @@
-This file is used to check if the user tries to run Rustlings in the repository (the method before v6)
+This file is used to check if the user tries to run Rustlings in the repository (the method before version 6)

exercises/04_primitive_types/README.md

@@ -5,5 +5,5 @@ compiler. In this section, we'll go through the most important ones.
 
 ## Further information
 
-- [Data Types](https://doc.rust-lang.org/stable/book/ch03-02-data-types.html)
-- [The Slice Type](https://doc.rust-lang.org/stable/book/ch04-03-slices.html)
+- [Data Types](https://doc.rust-lang.org/book/ch03-02-data-types.html)
+- [The Slice Type](https://doc.rust-lang.org/book/ch04-03-slices.html)

exercises/05_vecs/README.md

@@ -12,6 +12,6 @@ the other useful data structure, hash maps, later.
 
 ## Further information
 
-- [Storing Lists of Values with Vectors](https://doc.rust-lang.org/stable/book/ch08-01-vectors.html)
+- [Storing Lists of Values with Vectors](https://doc.rust-lang.org/book/ch08-01-vectors.html)
 - [`iter_mut`](https://doc.rust-lang.org/std/primitive.slice.html#method.iter_mut)
 - [`map`](https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.map)

exercises/06_move_semantics/move_semantics4.rs

@@ -7,12 +7,12 @@ mod tests {
     // TODO: Fix the compiler errors only by reordering the lines in the test.
     // Don't add, change or remove any line.
     #[test]
-    fn move_semantics5() {
-        let mut x = 100;
+    fn move_semantics4() {
+        let mut x = Vec::new();
         let y = &mut x;
         let z = &mut x;
-        *y += 100;
-        *z += 1000;
-        assert_eq!(x, 1200);
+        y.push(42);
+        z.push(13);
+        assert_eq!(x, [42, 13]);
     }
 }

exercises/06_move_semantics/move_semantics5.rs

@@ -3,14 +3,6 @@
 // TODO: Fix the compiler errors without changing anything except adding or
 // removing references (the character `&`).
 
-fn main() {
-    let data = "Rust is great!".to_string();
-
-    get_char(data);
-
-    string_uppercase(&data);
-}
-
 // Shouldn't take ownership
 fn get_char(data: String) -> char {
     data.chars().last().unwrap()
@@ -22,3 +14,11 @@ fn string_uppercase(mut data: &String) {
 
     println!("{data}");
 }
+
+fn main() {
+    let data = "Rust is great!".to_string();
+
+    get_char(data);
+
+    string_uppercase(&data);
+}

exercises/07_structs/structs3.rs

@@ -1,5 +1,5 @@
-// Structs contain data, but can also have logic. In this exercise we have
-// defined the `Package` struct and we want to test some logic attached to it.
+// Structs contain data, but can also have logic. In this exercise, we have
+// defined the `Package` struct, and we want to test some logic attached to it.
 
 #[derive(Debug)]
 struct Package {

exercises/08_enums/enums1.rs

@@ -4,8 +4,9 @@ enum Message {
 }
 
 fn main() {
-    println!("{:?}", Message::Quit);
-    println!("{:?}", Message::Echo);
+    println!("{:?}", Message::Resize);
     println!("{:?}", Message::Move);
+    println!("{:?}", Message::Echo);
     println!("{:?}", Message::ChangeColor);
+    println!("{:?}", Message::Quit);
 }

exercises/08_enums/enums2.rs

@@ -1,4 +1,11 @@
-#[allow(dead_code)]
+#![allow(dead_code)]
+
+#[derive(Debug)]
+struct Point {
+    x: u64,
+    y: u64,
+}
+
 #[derive(Debug)]
 enum Message {
     // TODO: Define the different variants used below.
@@ -12,7 +19,11 @@ impl Message {
 
 fn main() {
     let messages = [
-        Message::Move { x: 10, y: 30 },
+        Message::Resize {
+            width: 10,
+            height: 30,
+        },
+        Message::Move(Point { x: 10, y: 15 }),
         Message::Echo(String::from("hello world")),
         Message::ChangeColor(200, 255, 255),
         Message::Quit,

exercises/08_enums/enums3.rs

@@ -1,40 +1,47 @@
+struct Point {
+    x: u64,
+    y: u64,
+}
+
 enum Message {
     // TODO: Implement the message variant types based on their usage below.
 }
 
-struct Point {
-    x: u8,
-    y: u8,
-}
-
 struct State {
-    color: (u8, u8, u8),
+    width: u64,
+    height: u64,
     position: Point,
-    quit: bool,
     message: String,
+    // RGB color composed of red, green and blue.
+    color: (u8, u8, u8),
+    quit: bool,
 }
 
 impl State {
-    fn change_color(&mut self, color: (u8, u8, u8)) {
-        self.color = color;
-    }
-
-    fn quit(&mut self) {
-        self.quit = true;
-    }
-
-    fn echo(&mut self, s: String) {
-        self.message = s;
+    fn resize(&mut self, width: u64, height: u64) {
+        self.width = width;
+        self.height = height;
     }
 
     fn move_position(&mut self, point: Point) {
         self.position = point;
     }
 
+    fn echo(&mut self, s: String) {
+        self.message = s;
+    }
+
+    fn change_color(&mut self, red: u8, green: u8, blue: u8) {
+        self.color = (red, green, blue);
+    }
+
+    fn quit(&mut self) {
+        self.quit = true;
+    }
+
     fn process(&mut self, message: Message) {
-        // TODO: Create a match expression to process the different message variants.
-        // Remember: When passing a tuple as a function argument, you'll need extra parentheses:
-        // e.g. `foo((t, u, p, l, e))`
+        // TODO: Create a match expression to process the different message
+        // variants using the methods defined above.
     }
 }
 
@@ -49,21 +56,29 @@ mod tests {
     #[test]
     fn test_match_message_call() {
         let mut state = State {
-            quit: false,
+            width: 0,
+            height: 0,
             position: Point { x: 0, y: 0 },
-            color: (0, 0, 0),
             message: String::from("hello world"),
+            color: (0, 0, 0),
+            quit: false,
         };
 
-        state.process(Message::ChangeColor(255, 0, 255));
-        state.process(Message::Echo(String::from("Hello world!")));
+        state.process(Message::Resize {
+            width: 10,
+            height: 30,
+        });
         state.process(Message::Move(Point { x: 10, y: 15 }));
+        state.process(Message::Echo(String::from("Hello world!")));
+        state.process(Message::ChangeColor(255, 0, 255));
         state.process(Message::Quit);
 
-        assert_eq!(state.color, (255, 0, 255));
+        assert_eq!(state.width, 10);
+        assert_eq!(state.height, 30);
         assert_eq!(state.position.x, 10);
         assert_eq!(state.position.y, 15);
-        assert!(state.quit);
         assert_eq!(state.message, "Hello world!");
+        assert_eq!(state.color, (255, 0, 255));
+        assert!(state.quit);
     }
 }

exercises/09_strings/strings4.rs

@@ -4,6 +4,7 @@ fn placeholder() {}
 fn string_slice(arg: &str) {
     println!("{arg}");
 }
+
 fn string(arg: String) {
     println!("{arg}");
 }

exercises/11_hashmaps/hashmaps2.rs

@@ -5,7 +5,8 @@
 // Apple (4), Mango (2) and Lychee (5) are already in the basket hash map. You
 // must add fruit to the basket so that there is at least one of each kind and
 // more than 11 in total - we have a lot of mouths to feed. You are not allowed
-// to insert any more of these fruits!
+// to insert any more of the fruits that are already in the basket (Apple,
+// Mango, and Lychee).
 
 use std::collections::HashMap;
 

exercises/11_hashmaps/hashmaps3.rs

@@ -10,12 +10,12 @@ use std::collections::HashMap;
 
 // A structure to store the goal details of a team.
 #[derive(Default)]
-struct Team {
+struct TeamScores {
     goals_scored: u8,
     goals_conceded: u8,
 }
 
-fn build_scores_table(results: &str) -> HashMap<&str, Team> {
+fn build_scores_table(results: &str) -> HashMap<&str, TeamScores> {
     // The name of the team is the key and its associated struct is the value.
     let mut scores = HashMap::new();
 

exercises/12_options/README.md

@@ -14,7 +14,7 @@ Option types are very common in Rust code, as they have a number of uses:
 
 ## Further Information
 
-- [Option Enum Format](https://doc.rust-lang.org/stable/book/ch10-01-syntax.html#in-enum-definitions)
+- [Option Enum Format](https://doc.rust-lang.org/book/ch10-01-syntax.html#in-enum-definitions)
 - [Option Module Documentation](https://doc.rust-lang.org/std/option/)
 - [Option Enum Documentation](https://doc.rust-lang.org/std/option/enum.Option.html)
 - [if let](https://doc.rust-lang.org/rust-by-example/flow_control/if_let.html)

exercises/13_error_handling/errors3.rs

@@ -19,6 +19,7 @@ fn main() {
     let mut tokens = 100;
     let pretend_user_input = "8";
 
+    // Don't change this line.
     let cost = total_cost(pretend_user_input)?;
 
     if cost > tokens {

exercises/13_error_handling/errors5.rs

@@ -39,8 +39,8 @@ struct PositiveNonzeroInteger(u64);
 impl PositiveNonzeroInteger {
     fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
         match value {
-            0 => Err(CreationError::Zero),
             x if x < 0 => Err(CreationError::Negative),
+            0 => Err(CreationError::Zero),
             x => Ok(PositiveNonzeroInteger(x as u64)),
         }
     }

exercises/13_error_handling/errors6.rs

@@ -25,7 +25,7 @@ impl ParsePosNonzeroError {
     }
 
     // TODO: Add another error conversion function here.
-    // fn from_parseint(???) -> Self { ??? }
+    // fn from_parse_int(???) -> Self { ??? }
 }
 
 #[derive(PartialEq, Debug)]

exercises/14_generics/README.md

@@ -7,5 +7,5 @@ The simplest and most common use of generics is for type parameters.
 
 ## Further information
 
-- [Generic Data Types](https://doc.rust-lang.org/stable/book/ch10-01-syntax.html)
+- [Generic Data Types](https://doc.rust-lang.org/book/ch10-01-syntax.html)
 - [Bounds](https://doc.rust-lang.org/rust-by-example/generics/bounds.html)

exercises/17_tests/tests3.rs

@@ -9,7 +9,7 @@ impl Rectangle {
         if width <= 0 || height <= 0 {
             // Returning a `Result` would be better here. But we want to learn
             // how to test functions that can panic.
-            panic!("Rectangle width and height can't be negative");
+            panic!("Rectangle width and height must be positive");
         }
 
         Rectangle { width, height }

exercises/18_iterators/iterators3.rs

@@ -1,12 +1,16 @@
 #[derive(Debug, PartialEq, Eq)]
 enum DivisionError {
+    // Example: 42 / 0
     DivideByZero,
+    // Only case for `i64`: `i64::MIN / -1` because the result is `i64::MAX + 1`
+    IntegerOverflow,
+    // Example: 5 / 2 = 2.5
     NotDivisible,
 }
 
 // TODO: Calculate `a` divided by `b` if `a` is evenly divisible by `b`.
 // Otherwise, return a suitable error.
-fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {
+fn divide(a: i64, b: i64) -> Result<i64, DivisionError> {
     todo!();
 }
 
@@ -42,6 +46,11 @@ mod tests {
         assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
     }
 
+    #[test]
+    fn test_integer_overflow() {
+        assert_eq!(divide(i64::MIN, -1), Err(DivisionError::IntegerOverflow));
+    }
+
     #[test]
     fn test_not_divisible() {
         assert_eq!(divide(81, 6), Err(DivisionError::NotDivisible));

exercises/18_iterators/iterators4.rs

@@ -1,5 +1,8 @@
-fn factorial(num: u8) -> u64 {
-    // TODO: Complete this function to return the factorial of `num`.
+fn factorial(num: u64) -> u64 {
+    // TODO: Complete this function to return the factorial of `num` which is
+    // defined as `1 * 2 * 3 * … * num`.
+    // https://en.wikipedia.org/wiki/Factorial
+    //
     // Do not use:
     // - early returns (using the `return` keyword explicitly)
     // Try not to use:

exercises/19_smart_pointers/cow1.rs

@@ -45,8 +45,9 @@ mod tests {
     #[test]
     fn owned_no_mutation() {
         // We can also pass `vec` without `&` so `Cow` owns it directly. In this
-        // case, no mutation occurs and thus also no clone. But the result is
-        // still owned because it was never borrowed or mutated.
+        // case, no mutation occurs (all numbers are already absolute) and thus
+        // also no clone. But the result is still owned because it was never
+        // borrowed or mutated.
         let vec = vec![0, 1, 2];
         let mut input = Cow::from(vec);
         abs_all(&mut input);
@@ -56,9 +57,9 @@ mod tests {
 
     #[test]
     fn owned_mutation() {
-        // Of course this is also the case if a mutation does occur. In this
-        // case, the call to `to_mut()` in the `abs_all` function returns a
-        // reference to the same data as before.
+        // Of course this is also the case if a mutation does occur (not all
+        // numbers are absolute). In this case, the call to `to_mut()` in the
+        // `abs_all` function returns a reference to the same data as before.
         let vec = vec![-1, 0, 1];
         let mut input = Cow::from(vec);
         abs_all(&mut input);

exercises/quizzes/quiz1.rs

@@ -5,12 +5,12 @@
 //
 // Mary is buying apples. The price of an apple is calculated as follows:
 // - An apple costs 2 rustbucks.
-// - If Mary buys more than 40 apples, each apple only costs 1 rustbuck!
+// - However, if Mary buys more than 40 apples, the price of each apple in the
+// entire order is reduced to only 1 rustbuck!
+
 // TODO: Write a function that calculates the price of an order of apples given
 // the quantity bought.
-
-// Put your function here!
-// fn calculate_price_of_apples(???) -> ??? {
+// fn calculate_price_of_apples(???) -> ??? { ??? }
 
 fn main() {
     // You can optionally experiment here.

exercises/quizzes/quiz2.rs

@@ -26,7 +26,7 @@ enum Command {
 mod my_module {
     use super::Command;
 
-    // TODO: Complete the function.
+    // TODO: Complete the function as described above.
     // pub fn transformer(input: ???) -> ??? { ??? }
 }
 

release-hook.sh

@@ -3,7 +3,11 @@
 # Error out if any command fails
 set -e
 
-cargo run -- dev check
 typos
-cargo outdated -w --exit-code 1
+cargo upgrades
+
+# Similar to CI
+cargo clippy -- --deny warnings
+cargo fmt --all --check
 cargo test --workspace --all-targets
+cargo run -- dev check --require-solutions

rustlings-macros/Cargo.toml

@@ -6,6 +6,7 @@ authors.workspace = true
 repository.workspace = true
 license.workspace = true
 edition.workspace = true
+rust-version.workspace = true
 include = [
   "/src/",
   "/info.toml",

rustlings-macros/info.toml

@@ -31,6 +31,7 @@ https://github.com/rust-lang/rustlings/blob/main/CONTRIBUTING.md"""
 name = "intro1"
 dir = "00_intro"
 test = false
+skip_check_unsolved = true
 hint = """
 Enter `n` to move on to the next exercise.
 You might need to press ENTER after typing `n`."""
@@ -308,7 +309,7 @@ In Rust, there are two ways to define a Vector.
    inside the square brackets. This way is simpler when you exactly know
    the initial values.
 
-Check this chapter: https://doc.rust-lang.org/stable/book/ch08-01-vectors.html
+Check this chapter: https://doc.rust-lang.org/book/ch08-01-vectors.html
 of the Rust book to learn more."""
 
 [[exercises]]
@@ -350,7 +351,7 @@ We call this "moving" a variable. When we pass `vec0` into `fill_vec`, it's
 being "moved" into `vec1`, meaning we can't access `vec0` anymore.
 
 You could make another, separate version of the data that's in `vec0` and
-pass it to `fill_vec` instead."""
+pass it to `fill_vec` instead. This is called cloning in Rust."""
 
 [[exercises]]
 name = "move_semantics3"
@@ -377,7 +378,7 @@ dir = "06_move_semantics"
 test = false
 hint = """
 To find the answer, you can consult the book section "References and Borrowing":
-https://doc.rust-lang.org/stable/book/ch04-02-references-and-borrowing.html
+https://doc.rust-lang.org/book/ch04-02-references-and-borrowing.html
 
 The first problem is that `get_char` is taking ownership of the string. So
 `data` is moved and can't be used for `string_uppercase`. `data` is moved to
@@ -415,7 +416,7 @@ to its fields.
 
 There are however some shortcuts that can be taken when instantiating structs.
 Have a look in The Book to find out more:
-https://doc.rust-lang.org/stable/book/ch05-01-defining-structs.html#creating-instances-from-other-instances-with-struct-update-syntax"""
+https://doc.rust-lang.org/book/ch05-01-defining-structs.html#creating-instances-from-other-instances-with-struct-update-syntax"""
 
 [[exercises]]
 name = "structs3"
@@ -444,7 +445,7 @@ dir = "08_enums"
 test = false
 hint = """
 You can create enumerations that have different variants with different types
-such as no data, anonymous structs, a single string, tuples, etc."""
+such as anonymous structs, structs, a single string, tuples, no data, etc."""
 
 [[exercises]]
 name = "enums3"
@@ -486,7 +487,7 @@ to add one character to the `if` statement, though, that will coerce the
 Side note: If you're interested in learning about how this kind of reference
 conversion works, you can jump ahead in the book and read this part in the
 smart pointers chapter:
-https://doc.rust-lang.org/stable/book/ch15-02-deref.html#implicit-deref-coercions-with-functions-and-methods"""
+https://doc.rust-lang.org/book/ch15-02-deref.html#implicit-deref-coercions-with-functions-and-methods"""
 
 [[exercises]]
 name = "strings3"
@@ -497,7 +498,10 @@ some of them:
 https://doc.rust-lang.org/std/string/struct.String.html#method.trim
 
 For the `compose_me` method: You can either use the `format!` macro, or convert
-the string slice into an owned string, which you can then freely extend."""
+the string slice into an owned string, which you can then freely extend.
+
+For the `replace_me` method, you can check out the `replace` method:
+https://doc.rust-lang.org/std/string/struct.String.html#method.replace"""
 
 [[exercises]]
 name = "strings4"
@@ -560,18 +564,18 @@ hint = """
 Use the `entry()` and `or_insert()` methods of `HashMap` to achieve this.
 
 Learn more in The Book:
-https://doc.rust-lang.org/stable/book/ch08-03-hash-maps.html#only-inserting-a-value-if-the-key-has-no-value"""
+https://doc.rust-lang.org/book/ch08-03-hash-maps.html#only-inserting-a-value-if-the-key-has-no-value"""
 
 [[exercises]]
 name = "hashmaps3"
 dir = "11_hashmaps"
 hint = """
 Hint 1: Use the `entry()` and `or_insert()` (or `or_insert_with()`) methods of
-        `HashMap` to insert the default value of `Team` if a team doesn't
+        `HashMap` to insert the default value of `TeamScores` if a team doesn't
         exist in the table yet.
 
 Learn more in The Book:
-https://doc.rust-lang.org/stable/book/ch08-03-hash-maps.html#only-inserting-a-value-if-the-key-has-no-value
+https://doc.rust-lang.org/book/ch08-03-hash-maps.html#only-inserting-a-value-if-the-key-has-no-value
 
 Hint 2: If there is already an entry for a given key, the value returned by
         `entry()` can be updated based on the existing value.
@@ -584,7 +588,7 @@ https://doc.rust-lang.org/book/ch08-03-hash-maps.html#updating-a-value-based-on-
 [[exercises]]
 name = "quiz2"
 dir = "quizzes"
-hint = "No hints this time ;)"
+hint = "The `+` operator can concatenate a `String` with a `&str`."
 
 # OPTIONS
 
@@ -738,7 +742,7 @@ name = "generics2"
 dir = "14_generics"
 hint = """
 Related section in The Book:
-https://doc.rust-lang.org/stable/book/ch10-01-syntax.html#in-method-definitions"""
+https://doc.rust-lang.org/book/ch10-01-syntax.html#in-method-definitions"""
 
 # TRAITS
 
@@ -747,7 +751,9 @@ name = "traits1"
 dir = "15_traits"
 hint = """
 More about traits in The Book:
-https://doc.rust-lang.org/book/ch10-02-traits.html"""
+https://doc.rust-lang.org/book/ch10-02-traits.html
+
+The `+` operator can concatenate a `String` with a `&str`."""
 
 [[exercises]]
 name = "traits2"
@@ -868,7 +874,7 @@ We expect the method `Rectangle::new` to panic for negative values.
 To handle that, you need to add a special attribute to the test function.
 
 You can refer to the docs:
-https://doc.rust-lang.org/stable/book/ch11-01-writing-tests.html#checking-for-panics-with-should_panic"""
+https://doc.rust-lang.org/book/ch11-01-writing-tests.html#checking-for-panics-with-should_panic"""
 
 # STANDARD LIBRARY TYPES
 
@@ -887,9 +893,9 @@ hint = """
 `capitalize_first`:
 
 The variable `first` is a `char`. It needs to be capitalized and added to the
-remaining characters in `c` in order to return the correct `String`.
+remaining characters in `chars` in order to return the correct `String`.
 
-The remaining characters in `c` can be viewed as a string slice using the
+The remaining characters in `chars` can be viewed as a string slice using the
 `as_str` method.
 
 The documentation for `char` contains many useful methods.
@@ -1004,7 +1010,7 @@ thread-local copy of the numbers.
 This is a simple exercise if you understand the underlying concepts, but if this
 is too much of a struggle, consider reading through all of Chapter 16 in The
 Book:
-https://doc.rust-lang.org/stable/book/ch16-00-concurrency.html"""
+https://doc.rust-lang.org/book/ch16-00-concurrency.html"""
 
 [[exercises]]
 name = "cow1"
@@ -1142,7 +1148,11 @@ test = false
 strict_clippy = true
 hint = """
 `for` loops over `Option` values are more clearly expressed as an `if-let`
-statement."""
+statement.
+
+Not required to solve this exercise, but if you are interested in when iterating
+over `Option` can be useful, read the following section in the documentation:
+https://doc.rust-lang.org/std/option/#iterating-over-option"""
 
 [[exercises]]
 name = "clippy3"

solutions/06_move_semantics/move_semantics4.rs

@@ -7,15 +7,15 @@ mod tests {
     // TODO: Fix the compiler errors only by reordering the lines in the test.
     // Don't add, change or remove any line.
     #[test]
-    fn move_semantics5() {
-        let mut x = 100;
+    fn move_semantics4() {
+        let mut x = Vec::new();
         let y = &mut x;
         // `y` used here.
-        *y += 100;
+        y.push(42);
         // The mutable reference `y` is not used anymore,
         // therefore a new reference can be created.
         let z = &mut x;
-        *z += 1000;
-        assert_eq!(x, 1200);
+        z.push(13);
+        assert_eq!(x, [42, 13]);
     }
 }

solutions/06_move_semantics/move_semantics5.rs

@@ -1,13 +1,5 @@
 #![allow(clippy::ptr_arg)]
 
-fn main() {
-    let data = "Rust is great!".to_string();
-
-    get_char(&data);
-
-    string_uppercase(data);
-}
-
 // Borrows instead of taking ownership.
 // It is recommended to use `&str` instead of `&String` here. But this is
 // enough for now because we didn't handle strings yet.
@@ -21,3 +13,11 @@ fn string_uppercase(mut data: String) {
 
     println!("{data}");
 }
+
+fn main() {
+    let data = "Rust is great!".to_string();
+
+    get_char(&data);
+
+    string_uppercase(data);
+}

solutions/08_enums/enums1.rs

@@ -1,14 +1,16 @@
 #[derive(Debug)]
 enum Message {
-    Quit,
-    Echo,
+    Resize,
     Move,
+    Echo,
     ChangeColor,
+    Quit,
 }
 
 fn main() {
-    println!("{:?}", Message::Quit);
-    println!("{:?}", Message::Echo);
+    println!("{:?}", Message::Resize);
     println!("{:?}", Message::Move);
+    println!("{:?}", Message::Echo);
     println!("{:?}", Message::ChangeColor);
+    println!("{:?}", Message::Quit);
 }

solutions/08_enums/enums2.rs

@@ -1,7 +1,15 @@
-#[allow(dead_code)]
+#![allow(dead_code)]
+
+#[derive(Debug)]
+struct Point {
+    x: u64,
+    y: u64,
+}
+
 #[derive(Debug)]
 enum Message {
-    Move { x: i64, y: i64 },
+    Resize { width: u64, height: u64 },
+    Move(Point),
     Echo(String),
     ChangeColor(u8, u8, u8),
     Quit,
@@ -15,7 +23,11 @@ impl Message {
 
 fn main() {
     let messages = [
-        Message::Move { x: 10, y: 30 },
+        Message::Resize {
+            width: 10,
+            height: 30,
+        },
+        Message::Move(Point { x: 10, y: 15 }),
         Message::Echo(String::from("hello world")),
         Message::ChangeColor(200, 255, 255),
         Message::Quit,

solutions/08_enums/enums3.rs

@@ -1,44 +1,53 @@
+struct Point {
+    x: u64,
+    y: u64,
+}
+
 enum Message {
-    ChangeColor(u8, u8, u8),
-    Echo(String),
+    Resize { width: u64, height: u64 },
     Move(Point),
+    Echo(String),
+    ChangeColor(u8, u8, u8),
     Quit,
 }
 
-struct Point {
-    x: u8,
-    y: u8,
-}
-
 struct State {
-    color: (u8, u8, u8),
+    width: u64,
+    height: u64,
     position: Point,
-    quit: bool,
     message: String,
+    color: (u8, u8, u8),
+    quit: bool,
 }
 
 impl State {
-    fn change_color(&mut self, color: (u8, u8, u8)) {
-        self.color = color;
-    }
-
-    fn quit(&mut self) {
-        self.quit = true;
-    }
-
-    fn echo(&mut self, s: String) {
-        self.message = s;
+    fn resize(&mut self, width: u64, height: u64) {
+        self.width = width;
+        self.height = height;
     }
 
     fn move_position(&mut self, point: Point) {
         self.position = point;
     }
 
+    fn echo(&mut self, s: String) {
+        self.message = s;
+    }
+
+    fn change_color(&mut self, red: u8, green: u8, blue: u8) {
+        self.color = (red, green, blue);
+    }
+
+    fn quit(&mut self) {
+        self.quit = true;
+    }
+
     fn process(&mut self, message: Message) {
         match message {
-            Message::ChangeColor(r, g, b) => self.change_color((r, g, b)),
-            Message::Echo(s) => self.echo(s),
+            Message::Resize { width, height } => self.resize(width, height),
             Message::Move(point) => self.move_position(point),
+            Message::Echo(s) => self.echo(s),
+            Message::ChangeColor(r, g, b) => self.change_color(r, g, b),
             Message::Quit => self.quit(),
         }
     }
@@ -55,21 +64,29 @@ mod tests {
     #[test]
     fn test_match_message_call() {
         let mut state = State {
-            quit: false,
+            width: 0,
+            height: 0,
             position: Point { x: 0, y: 0 },
-            color: (0, 0, 0),
             message: String::from("hello world"),
+            color: (0, 0, 0),
+            quit: false,
         };
 
-        state.process(Message::ChangeColor(255, 0, 255));
-        state.process(Message::Echo(String::from("Hello world!")));
+        state.process(Message::Resize {
+            width: 10,
+            height: 30,
+        });
         state.process(Message::Move(Point { x: 10, y: 15 }));
+        state.process(Message::Echo(String::from("Hello world!")));
+        state.process(Message::ChangeColor(255, 0, 255));
         state.process(Message::Quit);
 
-        assert_eq!(state.color, (255, 0, 255));
+        assert_eq!(state.width, 10);
+        assert_eq!(state.height, 30);
         assert_eq!(state.position.x, 10);
         assert_eq!(state.position.y, 15);
-        assert!(state.quit);
         assert_eq!(state.message, "Hello world!");
+        assert_eq!(state.color, (255, 0, 255));
+        assert!(state.quit);
     }
 }

solutions/09_strings/strings4.rs

@@ -1,6 +1,7 @@
 fn string_slice(arg: &str) {
     println!("{arg}");
 }
+
 fn string(arg: String) {
     println!("{arg}");
 }

solutions/11_hashmaps/hashmaps2.rs

@@ -5,7 +5,8 @@
 // Apple (4), Mango (2) and Lychee (5) are already in the basket hash map. You
 // must add fruit to the basket so that there is at least one of each kind and
 // more than 11 in total - we have a lot of mouths to feed. You are not allowed
-// to insert any more of these fruits!
+// to insert any more of the fruits that are already in the basket (Apple,
+// Mango, and Lychee).
 
 use std::collections::HashMap;
 

solutions/11_hashmaps/hashmaps3.rs

@@ -10,12 +10,12 @@ use std::collections::HashMap;
 
 // A structure to store the goal details of a team.
 #[derive(Default)]
-struct Team {
+struct TeamScores {
     goals_scored: u8,
     goals_conceded: u8,
 }
 
-fn build_scores_table(results: &str) -> HashMap<&str, Team> {
+fn build_scores_table(results: &str) -> HashMap<&str, TeamScores> {
     // The name of the team is the key and its associated struct is the value.
     let mut scores = HashMap::new();
 
@@ -28,13 +28,17 @@ fn build_scores_table(results: &str) -> HashMap<&str, Team> {
         let team_2_score: u8 = split_iterator.next().unwrap().parse().unwrap();
 
         // Insert the default with zeros if a team doesn't exist yet.
-        let team_1 = scores.entry(team_1_name).or_insert_with(Team::default);
+        let team_1 = scores
+            .entry(team_1_name)
+            .or_insert_with(TeamScores::default);
         // Update the values.
         team_1.goals_scored += team_1_score;
         team_1.goals_conceded += team_2_score;
 
         // Similarely for the second team.
-        let team_2 = scores.entry(team_2_name).or_insert_with(Team::default);
+        let team_2 = scores
+            .entry(team_2_name)
+            .or_insert_with(TeamScores::default);
         team_2.goals_scored += team_2_score;
         team_2.goals_conceded += team_1_score;
     }

solutions/13_error_handling/errors6.rs

@@ -24,7 +24,7 @@ impl ParsePosNonzeroError {
         Self::Creation(err)
     }
 
-    fn from_parseint(err: ParseIntError) -> Self {
+    fn from_parse_int(err: ParseIntError) -> Self {
         Self::ParseInt(err)
     }
 }
@@ -44,7 +44,7 @@ impl PositiveNonzeroInteger {
     fn parse(s: &str) -> Result<Self, ParsePosNonzeroError> {
         // Return an appropriate error instead of panicking when `parse()`
         // returns an error.
-        let x: i64 = s.parse().map_err(ParsePosNonzeroError::from_parseint)?;
+        let x: i64 = s.parse().map_err(ParsePosNonzeroError::from_parse_int)?;
         //                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
         Self::new(x).map_err(ParsePosNonzeroError::from_creation)
     }

solutions/17_tests/tests3.rs

@@ -9,7 +9,7 @@ impl Rectangle {
         if width <= 0 || height <= 0 {
             // Returning a `Result` would be better here. But we want to learn
             // how to test functions that can panic.
-            panic!("Rectangle width and height can't be negative");
+            panic!("Rectangle width and height must be positive");
         }
 
         Rectangle { width, height }

solutions/18_iterators/iterators3.rs

@@ -1,6 +1,10 @@
 #[derive(Debug, PartialEq, Eq)]
 enum DivisionError {
+    // Example: 42 / 0
     DivideByZero,
+    // Only case for `i64`: `i64::MIN / -1` because the result is `i64::MAX + 1`
+    IntegerOverflow,
+    // Example: 5 / 2 = 2.5
     NotDivisible,
 }
 
@@ -9,6 +13,10 @@ fn divide(a: i64, b: i64) -> Result<i64, DivisionError> {
         return Err(DivisionError::DivideByZero);
     }
 
+    if a == i64::MIN && b == -1 {
+        return Err(DivisionError::IntegerOverflow);
+    }
+
     if a % b != 0 {
         return Err(DivisionError::NotDivisible);
     }
@@ -51,6 +59,11 @@ mod tests {
         assert_eq!(divide(81, 0), Err(DivisionError::DivideByZero));
     }
 
+    #[test]
+    fn test_integer_overflow() {
+        assert_eq!(divide(i64::MIN, -1), Err(DivisionError::IntegerOverflow));
+    }
+
     #[test]
     fn test_not_divisible() {
         assert_eq!(divide(81, 6), Err(DivisionError::NotDivisible));

solutions/18_iterators/iterators5.rs

@@ -47,6 +47,23 @@ fn count_collection_iterator(collection: &[HashMap<String, Progress>], value: Pr
         .sum()
 }
 
+// Equivalent to `count_collection_iterator` and `count_iterator`, iterating as
+// if the collection was a single container instead of a container of containers
+// (and more accurately, a single iterator instead of an iterator of iterators).
+fn count_collection_iterator_flat(
+    collection: &[HashMap<String, Progress>],
+    value: Progress,
+) -> usize {
+    // `collection` is a slice of hash maps.
+    // collection = [{ "variables1": Complete, "from_str": None, … },
+    //               { "variables2": Complete, … }, … ]
+    collection
+        .iter()
+        .flat_map(HashMap::values) // or just `.flatten()` when wanting the default iterator (`HashMap::iter`)
+        .filter(|val| **val == value)
+        .count()
+}
+
 fn main() {
     // You can optionally experiment here.
 }
@@ -54,10 +71,9 @@ fn main() {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use Progress::*;
 
     fn get_map() -> HashMap<String, Progress> {
-        use Progress::*;
-
         let mut map = HashMap::new();
         map.insert(String::from("variables1"), Complete);
         map.insert(String::from("functions1"), Complete);
@@ -70,8 +86,6 @@ mod tests {
     }
 
     fn get_vec_map() -> Vec<HashMap<String, Progress>> {
-        use Progress::*;
-
         let map = get_map();
 
         let mut other = HashMap::new();
@@ -87,25 +101,25 @@ mod tests {
     #[test]
     fn count_complete() {
         let map = get_map();
-        assert_eq!(count_iterator(&map, Progress::Complete), 3);
+        assert_eq!(count_iterator(&map, Complete), 3);
     }
 
     #[test]
     fn count_some() {
         let map = get_map();
-        assert_eq!(count_iterator(&map, Progress::Some), 1);
+        assert_eq!(count_iterator(&map, Some), 1);
     }
 
     #[test]
     fn count_none() {
         let map = get_map();
-        assert_eq!(count_iterator(&map, Progress::None), 2);
+        assert_eq!(count_iterator(&map, None), 2);
     }
 
     #[test]
     fn count_complete_equals_for() {
         let map = get_map();
-        let progress_states = [Progress::Complete, Progress::Some, Progress::None];
+        let progress_states = [Complete, Some, None];
         for progress_state in progress_states {
             assert_eq!(
                 count_for(&map, progress_state),
@@ -117,34 +131,38 @@ mod tests {
     #[test]
     fn count_collection_complete() {
         let collection = get_vec_map();
-        assert_eq!(
-            count_collection_iterator(&collection, Progress::Complete),
-            6,
-        );
+        assert_eq!(count_collection_iterator(&collection, Complete), 6);
+        assert_eq!(count_collection_iterator_flat(&collection, Complete), 6);
     }
 
     #[test]
     fn count_collection_some() {
         let collection = get_vec_map();
-        assert_eq!(count_collection_iterator(&collection, Progress::Some), 1);
+        assert_eq!(count_collection_iterator(&collection, Some), 1);
+        assert_eq!(count_collection_iterator_flat(&collection, Some), 1);
     }
 
     #[test]
     fn count_collection_none() {
         let collection = get_vec_map();
-        assert_eq!(count_collection_iterator(&collection, Progress::None), 4);
+        assert_eq!(count_collection_iterator(&collection, None), 4);
+        assert_eq!(count_collection_iterator_flat(&collection, None), 4);
     }
 
     #[test]
     fn count_collection_equals_for() {
         let collection = get_vec_map();
-        let progress_states = [Progress::Complete, Progress::Some, Progress::None];
+        let progress_states = [Complete, Some, None];
 
         for progress_state in progress_states {
             assert_eq!(
                 count_collection_for(&collection, progress_state),
                 count_collection_iterator(&collection, progress_state),
             );
+            assert_eq!(
+                count_collection_for(&collection, progress_state),
+                count_collection_iterator_flat(&collection, progress_state),
+            );
         }
     }
 }

solutions/19_smart_pointers/cow1.rs

@@ -45,8 +45,9 @@ mod tests {
     #[test]
     fn owned_no_mutation() {
         // We can also pass `vec` without `&` so `Cow` owns it directly. In this
-        // case, no mutation occurs and thus also no clone. But the result is
-        // still owned because it was never borrowed or mutated.
+        // case, no mutation occurs (all numbers are already absolute) and thus
+        // also no clone. But the result is still owned because it was never
+        // borrowed or mutated.
         let vec = vec![0, 1, 2];
         let mut input = Cow::from(vec);
         abs_all(&mut input);
@@ -56,9 +57,9 @@ mod tests {
 
     #[test]
     fn owned_mutation() {
-        // Of course this is also the case if a mutation does occur. In this
-        // case, the call to `to_mut()` in the `abs_all` function returns a
-        // reference to the same data as before.
+        // Of course this is also the case if a mutation does occur (not all
+        // numbers are absolute). In this case, the call to `to_mut()` in the
+        // `abs_all` function returns a reference to the same data as before.
         let vec = vec![-1, 0, 1];
         let mut input = Cow::from(vec);
         abs_all(&mut input);

solutions/23_conversions/as_ref_mut.rs

@@ -15,7 +15,7 @@ fn char_counter<T: AsRef<str>>(arg: T) -> usize {
 // Squares a number using `as_mut()`.
 fn num_sq<T: AsMut<u32>>(arg: &mut T) {
     let arg = arg.as_mut();
-    *arg = *arg * *arg;
+    *arg *= *arg;
 }
 
 fn main() {

solutions/README.md

@@ -0,0 +1,6 @@
+# Official Rustlings solutions
+
+Before you finish an exercise, its solution file will only contain an empty `main` function.
+The content of this file will be automatically replaced by the actual solution once you finish the exercise.
+
+Note that these solution are often only _one possibility_ to solve an exercise.

solutions/quizzes/quiz1.rs

@@ -1,8 +1,7 @@
 // Mary is buying apples. The price of an apple is calculated as follows:
 // - An apple costs 2 rustbucks.
-// - If Mary buys more than 40 apples, each apple only costs 1 rustbuck!
-// Write a function that calculates the price of an order of apples given the
-// quantity bought.
+// - However, if Mary buys more than 40 apples, the price of each apple in the
+// entire order is reduced to only 1 rustbuck!
 
 fn calculate_price_of_apples(n_apples: u64) -> u64 {
     if n_apples > 40 {

solutions/quizzes/quiz2.rs

@@ -1,10 +1,3 @@
-// This is a quiz for the following sections:
-// - Strings
-// - Vecs
-// - Move semantics
-// - Modules
-// - Enums
-//
 // Let's build a little machine in the form of a function. As input, we're going
 // to give a list of strings and commands. These commands determine what action
 // is going to be applied to the string. It can either be:
@@ -13,7 +6,7 @@
 // - Append "bar" to the string a specified amount of times
 //
 // The exact form of this will be:
-// - The input is going to be a vector of a 2-length tuple,
+// - The input is going to be a vector of 2-length tuples,
 //   the first element is the string, the second one is the command.
 // - The output element is going to be a vector of strings.
 
@@ -31,17 +24,12 @@ mod my_module {
     pub fn transformer(input: Vec<(String, Command)>) -> Vec<String> {
         let mut output = Vec::new();
 
-        for (mut string, command) in input {
+        for (string, command) in input {
             // Create the new string.
             let new_string = match command {
                 Command::Uppercase => string.to_uppercase(),
                 Command::Trim => string.trim().to_string(),
-                Command::Append(n) => {
-                    for _ in 0..n {
-                        string += "bar";
-                    }
-                    string
-                }
+                Command::Append(n) => string + &"bar".repeat(n),
             };
 
             // Push the new string to the output vector.
@@ -56,15 +44,10 @@ mod my_module {
     pub fn transformer_iter(input: Vec<(String, Command)>) -> Vec<String> {
         input
             .into_iter()
-            .map(|(mut string, command)| match command {
+            .map(|(string, command)| match command {
                 Command::Uppercase => string.to_uppercase(),
                 Command::Trim => string.trim().to_string(),
-                Command::Append(n) => {
-                    for _ in 0..n {
-                        string += "bar";
-                    }
-                    string
-                }
+                Command::Append(n) => string + &"bar".repeat(n),
             })
             .collect()
     }

solutions/quizzes/quiz3.rs

@@ -1,7 +1,3 @@
-// This quiz tests:
-// - Generics
-// - Traits
-//
 // An imaginary magical school has a new report card generation system written
 // in Rust! Currently, the system only supports creating report cards where the
 // student's grade is represented numerically (e.g. 1.0 -> 5.5). However, the

src/app_state.rs

@@ -1,19 +1,19 @@
-use anyhow::{bail, Context, Result};
-use crossterm::style::Stylize;
-use serde::Deserialize;
+use anyhow::{bail, Context, Error, Result};
 use std::{
     fs::{self, File},
     io::{Read, StdoutLock, Write},
-    path::{Path, PathBuf},
+    path::Path,
     process::{Command, Stdio},
+    thread,
 };
 
 use crate::{
     clear_terminal,
+    cmd::CmdRunner,
+    collections::hash_set_with_capacity,
     embedded::EMBEDDED_FILES,
-    exercise::{Exercise, RunnableExercise, OUTPUT_CAPACITY},
+    exercise::{Exercise, RunnableExercise},
     info_file::ExerciseInfo,
-    DEBUG_PROFILE,
 };
 
 const STATE_FILE_NAME: &str = ".rustlings-state.txt";
@@ -34,31 +34,6 @@ pub enum StateFileStatus {
     NotRead,
 }
 
-// Parses parts of the output of `cargo metadata`.
-#[derive(Deserialize)]
-struct CargoMetadata {
-    target_directory: PathBuf,
-}
-
-pub fn parse_target_dir() -> Result<PathBuf> {
-    // Get the target directory from Cargo.
-    let metadata_output = Command::new("cargo")
-        .arg("metadata")
-        .arg("-q")
-        .arg("--format-version")
-        .arg("1")
-        .arg("--no-deps")
-        .stdin(Stdio::null())
-        .stderr(Stdio::inherit())
-        .output()
-        .context(CARGO_METADATA_ERR)?
-        .stdout;
-
-    serde_json::de::from_slice::<CargoMetadata>(&metadata_output)
-        .context("Failed to read the field `target_directory` from the `cargo metadata` output")
-        .map(|metadata| metadata.target_directory)
-}
-
 pub struct AppState {
     current_exercise_ind: usize,
     exercises: Vec<Exercise>,
@@ -68,8 +43,7 @@ pub struct AppState {
     // Preallocated buffer for reading and writing the state file.
     file_buf: Vec<u8>,
     official_exercises: bool,
-    // Cargo's target directory.
-    target_dir: PathBuf,
+    cmd_runner: CmdRunner,
 }
 
 impl AppState {
@@ -96,7 +70,7 @@ impl AppState {
             return StateFileStatus::NotRead;
         }
 
-        let mut done_exercises = hashbrown::HashSet::with_capacity(self.exercises.len());
+        let mut done_exercises = hash_set_with_capacity(self.exercises.len());
 
         for done_exerise_name in lines {
             if done_exerise_name.is_empty() {
@@ -123,7 +97,7 @@ impl AppState {
         exercise_infos: Vec<ExerciseInfo>,
         final_message: String,
     ) -> Result<(Self, StateFileStatus)> {
-        let target_dir = parse_target_dir()?;
+        let cmd_runner = CmdRunner::build()?;
 
         let exercises = exercise_infos
             .into_iter()
@@ -134,8 +108,7 @@ impl AppState {
                 let path = exercise_info.path().leak();
                 let name = exercise_info.name.leak();
                 let dir = exercise_info.dir.map(|dir| &*dir.leak());
-
-                let hint = exercise_info.hint.trim().to_owned();
+                let hint = exercise_info.hint.leak().trim_ascii();
 
                 Exercise {
                     dir,
@@ -157,7 +130,7 @@ impl AppState {
             final_message,
             file_buf: Vec::with_capacity(2048),
             official_exercises: !Path::new("info.toml").exists(),
-            target_dir,
+            cmd_runner,
         };
 
         let state_file_status = slf.update_from_file();
@@ -186,8 +159,8 @@ impl AppState {
     }
 
     #[inline]
-    pub fn target_dir(&self) -> &Path {
-        &self.target_dir
+    pub fn cmd_runner(&self) -> &CmdRunner {
+        &self.cmd_runner
     }
 
     // Write the state file.
@@ -336,7 +309,7 @@ impl AppState {
     /// Official exercises: Dump the solution file form the binary and return its path.
     /// Third-party exercises: Check if a solution file exists and return its path in that case.
     pub fn current_solution_path(&self) -> Result<Option<String>> {
-        if DEBUG_PROFILE {
+        if cfg!(debug_assertions) {
             return Ok(None);
         }
 
@@ -373,40 +346,58 @@ impl AppState {
 
         if let Some(ind) = self.next_pending_exercise_ind() {
             self.set_current_exercise_ind(ind)?;
-
             return Ok(ExercisesProgress::NewPending);
         }
 
         writer.write_all(RERUNNING_ALL_EXERCISES_MSG)?;
 
-        let mut output = Vec::with_capacity(OUTPUT_CAPACITY);
-        for (exercise_ind, exercise) in self.exercises().iter().enumerate() {
-            write!(writer, "Running {exercise} ... ")?;
-            writer.flush()?;
+        let n_exercises = self.exercises.len();
 
-            let success = exercise.run_exercise(&mut output, &self.target_dir)?;
-            if !success {
-                writeln!(writer, "{}\n", "FAILED".red())?;
+        let pending_exercise_ind = thread::scope(|s| {
+            let handles = self
+                .exercises
+                .iter_mut()
+                .map(|exercise| {
+                    s.spawn(|| {
+                        let success = exercise.run_exercise(None, &self.cmd_runner)?;
+                        exercise.done = success;
+                        Ok::<_, Error>(success)
+                    })
+                })
+                .collect::<Vec<_>>();
 
-                self.current_exercise_ind = exercise_ind;
+            for (exercise_ind, handle) in handles.into_iter().enumerate() {
+                write!(writer, "\rProgress: {exercise_ind}/{n_exercises}")?;
+                writer.flush()?;
 
-                // No check if the exercise is done before setting it to pending
-                // because no pending exercise was found.
-                self.exercises[exercise_ind].done = false;
-                self.n_done -= 1;
-
-                self.write()?;
-
-                return Ok(ExercisesProgress::NewPending);
+                let success = handle.join().unwrap()?;
+                if !success {
+                    writer.write_all(b"\n\n")?;
+                    return Ok(Some(exercise_ind));
+                }
             }
 
-            writeln!(writer, "{}", "ok".green())?;
+            Ok::<_, Error>(None)
+        })?;
+
+        if let Some(pending_exercise_ind) = pending_exercise_ind {
+            self.current_exercise_ind = pending_exercise_ind;
+            self.n_done = self
+                .exercises
+                .iter()
+                .filter(|exercise| exercise.done)
+                .count() as u16;
+            self.write()?;
+            return Ok(ExercisesProgress::NewPending);
         }
 
+        // Write that the last exercise is done.
+        self.write()?;
+
         clear_terminal(writer)?;
         writer.write_all(FENISH_LINE.as_bytes())?;
 
-        let final_message = self.final_message.trim();
+        let final_message = self.final_message.trim_ascii();
         if !final_message.is_empty() {
             writer.write_all(final_message.as_bytes())?;
             writer.write_all(b"\n")?;
@@ -416,14 +407,9 @@ impl AppState {
     }
 }
 
-const CARGO_METADATA_ERR: &str = "Failed to run the command `cargo metadata …`
-Did you already install Rust?
-Try running `cargo --version` to diagnose the problem.";
-
 const RERUNNING_ALL_EXERCISES_MSG: &[u8] = b"
 All exercises seem to be done.
 Recompiling and running all exercises to make sure that all of them are actually done.
-
 ";
 
 const FENISH_LINE: &str = "+----------------------------------------------------+
@@ -459,7 +445,7 @@ mod tests {
             path: "exercises/0.rs",
             test: false,
             strict_clippy: false,
-            hint: String::new(),
+            hint: "",
             done: false,
         }
     }
@@ -473,7 +459,7 @@ mod tests {
             final_message: String::new(),
             file_buf: Vec::new(),
             official_exercises: true,
-            target_dir: PathBuf::new(),
+            cmd_runner: CmdRunner::build().unwrap(),
         };
 
         let mut assert = |done: [bool; 3], expected: [Option<usize>; 3]| {

src/cargo_toml.rs

@@ -111,6 +111,7 @@ mod tests {
                 test: true,
                 strict_clippy: true,
                 hint: String::new(),
+                skip_check_unsolved: false,
             },
             ExerciseInfo {
                 name: String::from("2"),
@@ -118,6 +119,7 @@ mod tests {
                 test: false,
                 strict_clippy: false,
                 hint: String::new(),
+                skip_check_unsolved: false,
             },
         ];
 

src/cmd.rs

@@ -1,30 +1,44 @@
-use anyhow::{Context, Result};
-use std::{io::Read, path::Path, process::Command};
+use anyhow::{bail, Context, Result};
+use serde::Deserialize;
+use std::{
+    io::Read,
+    path::PathBuf,
+    process::{Command, Stdio},
+};
 
 /// Run a command with a description for a possible error and append the merged stdout and stderr.
 /// The boolean in the returned `Result` is true if the command's exit status is success.
-pub fn run_cmd(mut cmd: Command, description: &str, output: &mut Vec<u8>) -> Result<bool> {
-    let (mut reader, writer) = os_pipe::pipe()
-        .with_context(|| format!("Failed to create a pipe to run the command `{description}``"))?;
+fn run_cmd(mut cmd: Command, description: &str, output: Option<&mut Vec<u8>>) -> Result<bool> {
+    let spawn = |mut cmd: Command| {
+        // NOTE: The closure drops `cmd` which prevents a pipe deadlock.
+        cmd.stdin(Stdio::null())
+            .spawn()
+            .with_context(|| format!("Failed to run the command `{description}`"))
+    };
 
-    let writer_clone = writer.try_clone().with_context(|| {
-        format!("Failed to clone the pipe writer for the command `{description}`")
-    })?;
+    let mut handle = if let Some(output) = output {
+        let (mut reader, writer) = os_pipe::pipe().with_context(|| {
+            format!("Failed to create a pipe to run the command `{description}``")
+        })?;
 
-    let mut handle = cmd
-        .stdout(writer_clone)
-        .stderr(writer)
-        .spawn()
-        .with_context(|| format!("Failed to run the command `{description}`"))?;
+        let writer_clone = writer.try_clone().with_context(|| {
+            format!("Failed to clone the pipe writer for the command `{description}`")
+        })?;
 
-    // Prevent pipe deadlock.
-    drop(cmd);
+        cmd.stdout(writer_clone).stderr(writer);
+        let handle = spawn(cmd)?;
 
-    reader
-        .read_to_end(output)
-        .with_context(|| format!("Failed to read the output of the command `{description}`"))?;
+        reader
+            .read_to_end(output)
+            .with_context(|| format!("Failed to read the output of the command `{description}`"))?;
 
-    output.push(b'\n');
+        output.push(b'\n');
+
+        handle
+    } else {
+        cmd.stdout(Stdio::null()).stderr(Stdio::null());
+        spawn(cmd)?
+    };
 
     handle
         .wait()
@@ -32,50 +46,104 @@ pub fn run_cmd(mut cmd: Command, description: &str, output: &mut Vec<u8>) -> Res
         .map(|status| status.success())
 }
 
-pub struct CargoCmd<'a> {
-    pub subcommand: &'a str,
-    pub args: &'a [&'a str],
-    pub bin_name: &'a str,
-    pub description: &'a str,
-    /// RUSTFLAGS="-A warnings"
-    pub hide_warnings: bool,
-    /// Added as `--target-dir` if `Self::dev` is true.
-    pub target_dir: &'a Path,
-    /// The output buffer to append the merged stdout and stderr.
-    pub output: &'a mut Vec<u8>,
-    /// true while developing Rustlings.
-    pub dev: bool,
+// Parses parts of the output of `cargo metadata`.
+#[derive(Deserialize)]
+struct CargoMetadata {
+    target_directory: PathBuf,
 }
 
-impl<'a> CargoCmd<'a> {
-    /// Run `cargo SUBCOMMAND --bin EXERCISE_NAME … ARGS`.
-    pub fn run(&mut self) -> Result<bool> {
+pub struct CmdRunner {
+    target_dir: PathBuf,
+}
+
+impl CmdRunner {
+    pub fn build() -> Result<Self> {
+        // Get the target directory from Cargo.
+        let metadata_output = Command::new("cargo")
+            .arg("metadata")
+            .arg("-q")
+            .arg("--format-version")
+            .arg("1")
+            .arg("--no-deps")
+            .stdin(Stdio::null())
+            .stderr(Stdio::inherit())
+            .output()
+            .context(CARGO_METADATA_ERR)?;
+
+        if !metadata_output.status.success() {
+            bail!("The command `cargo metadata …` failed. Are you in the `rustlings/` directory?");
+        }
+
+        let target_dir = serde_json::de::from_slice::<CargoMetadata>(&metadata_output.stdout)
+            .context(
+                "Failed to read the field `target_directory` from the output of the command `cargo metadata …`",
+            )?.target_directory;
+
+        Ok(Self { target_dir })
+    }
+
+    pub fn cargo<'out>(
+        &self,
+        subcommand: &str,
+        bin_name: &str,
+        output: Option<&'out mut Vec<u8>>,
+    ) -> CargoSubcommand<'out> {
         let mut cmd = Command::new("cargo");
-        cmd.arg(self.subcommand);
+        cmd.arg(subcommand).arg("-q").arg("--bin").arg(bin_name);
 
         // A hack to make `cargo run` work when developing Rustlings.
-        if self.dev {
-            cmd.arg("--manifest-path")
-                .arg("dev/Cargo.toml")
-                .arg("--target-dir")
-                .arg(self.target_dir);
+        #[cfg(debug_assertions)]
+        cmd.arg("--manifest-path")
+            .arg("dev/Cargo.toml")
+            .arg("--target-dir")
+            .arg(&self.target_dir);
+
+        if output.is_some() {
+            cmd.arg("--color").arg("always");
         }
 
-        cmd.arg("--color")
-            .arg("always")
-            .arg("-q")
-            .arg("--bin")
-            .arg(self.bin_name)
-            .args(self.args);
+        CargoSubcommand { cmd, output }
+    }
 
-        if self.hide_warnings {
-            cmd.env("RUSTFLAGS", "-A warnings");
-        }
+    /// The boolean in the returned `Result` is true if the command's exit status is success.
+    pub fn run_debug_bin(&self, bin_name: &str, output: Option<&mut Vec<u8>>) -> Result<bool> {
+        // 7 = "/debug/".len()
+        let mut bin_path =
+            PathBuf::with_capacity(self.target_dir.as_os_str().len() + 7 + bin_name.len());
+        bin_path.push(&self.target_dir);
+        bin_path.push("debug");
+        bin_path.push(bin_name);
 
-        run_cmd(cmd, self.description, self.output)
+        run_cmd(Command::new(&bin_path), &bin_path.to_string_lossy(), output)
     }
 }
 
+pub struct CargoSubcommand<'out> {
+    cmd: Command,
+    output: Option<&'out mut Vec<u8>>,
+}
+
+impl<'out> CargoSubcommand<'out> {
+    #[inline]
+    pub fn args<'arg, I>(&mut self, args: I) -> &mut Self
+    where
+        I: IntoIterator<Item = &'arg str>,
+    {
+        self.cmd.args(args);
+        self
+    }
+
+    /// The boolean in the returned `Result` is true if the command's exit status is success.
+    #[inline]
+    pub fn run(self, description: &str) -> Result<bool> {
+        run_cmd(self.cmd, description, self.output)
+    }
+}
+
+const CARGO_METADATA_ERR: &str = "Failed to run the command `cargo metadata …`
+Did you already install Rust?
+Try running `cargo --version` to diagnose the problem.";
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -86,7 +154,7 @@ mod tests {
         cmd.arg("Hello");
 
         let mut output = Vec::with_capacity(8);
-        run_cmd(cmd, "echo …", &mut output).unwrap();
+        run_cmd(cmd, "echo …", Some(&mut output)).unwrap();
 
         assert_eq!(output, b"Hello\n\n");
     }

src/collections.rs

@@ -0,0 +1,10 @@
+use ahash::AHasher;
+use std::hash::BuildHasherDefault;
+
+/// DOS attacks aren't a concern for Rustlings. Therefore, we use `ahash` with fixed seeds.
+pub type HashSet<T> = std::collections::HashSet<T, BuildHasherDefault<AHasher>>;
+
+#[inline]
+pub fn hash_set_with_capacity<T>(capacity: usize) -> HashSet<T> {
+    HashSet::with_capacity_and_hasher(capacity, BuildHasherDefault::<AHasher>::default())
+}

src/dev.rs

@@ -2,8 +2,6 @@ use anyhow::{bail, Context, Result};
 use clap::Subcommand;
 use std::path::PathBuf;
 
-use crate::DEBUG_PROFILE;
-
 mod check;
 mod new;
 mod update;
@@ -32,7 +30,7 @@ impl DevCommands {
     pub fn run(self) -> Result<()> {
         match self {
             Self::New { path, no_git } => {
-                if DEBUG_PROFILE {
+                if cfg!(debug_assertions) {
                     bail!("Disabled in the debug build");
                 }
 

src/dev/check.rs

@@ -1,22 +1,20 @@
-use anyhow::{anyhow, bail, Context, Result};
+use anyhow::{anyhow, bail, Context, Error, Result};
 use std::{
     cmp::Ordering,
     fs::{self, read_dir, OpenOptions},
     io::{self, Read, Write},
     path::{Path, PathBuf},
-    sync::{
-        atomic::{self, AtomicBool},
-        Mutex,
-    },
+    process::{Command, Stdio},
     thread,
 };
 
 use crate::{
-    app_state::parse_target_dir,
     cargo_toml::{append_bins, bins_start_end_ind, BINS_BUFFER_CAPACITY},
+    cmd::CmdRunner,
+    collections::{hash_set_with_capacity, HashSet},
     exercise::{RunnableExercise, OUTPUT_CAPACITY},
     info_file::{ExerciseInfo, InfoFile},
-    CURRENT_FORMAT_VERSION, DEBUG_PROFILE,
+    CURRENT_FORMAT_VERSION,
 };
 
 // Find a char that isn't allowed in the exercise's `name` or `dir`.
@@ -24,33 +22,36 @@ fn forbidden_char(input: &str) -> Option<char> {
     input.chars().find(|c| !c.is_alphanumeric() && *c != '_')
 }
 
-// Check that the Cargo.toml file is up-to-date.
+// Check that the `Cargo.toml` file is up-to-date.
 fn check_cargo_toml(
     exercise_infos: &[ExerciseInfo],
-    current_cargo_toml: &str,
+    cargo_toml_path: &str,
     exercise_path_prefix: &[u8],
 ) -> Result<()> {
-    let (bins_start_ind, bins_end_ind) = bins_start_end_ind(current_cargo_toml)?;
+    let current_cargo_toml = fs::read_to_string(cargo_toml_path)
+        .with_context(|| format!("Failed to read the file `{cargo_toml_path}`"))?;
+
+    let (bins_start_ind, bins_end_ind) = bins_start_end_ind(&current_cargo_toml)?;
 
     let old_bins = &current_cargo_toml.as_bytes()[bins_start_ind..bins_end_ind];
     let mut new_bins = Vec::with_capacity(BINS_BUFFER_CAPACITY);
     append_bins(&mut new_bins, exercise_infos, exercise_path_prefix);
 
     if old_bins != new_bins {
-        if DEBUG_PROFILE {
-            bail!("The file `dev/Cargo.toml` is outdated. Please run `cargo run -- dev update` to update it");
+        if cfg!(debug_assertions) {
+            bail!("The file `dev/Cargo.toml` is outdated. Please run `cargo run -- dev update` to update it. Then run `cargo run -- dev check` again");
         }
 
-        bail!("The file `Cargo.toml` is outdated. Please run `rustlings dev update` to update it");
+        bail!("The file `Cargo.toml` is outdated. Please run `rustlings dev update` to update it. Then run `rustlings dev check` again");
     }
 
     Ok(())
 }
 
 // Check the info of all exercises and return their paths in a set.
-fn check_info_file_exercises(info_file: &InfoFile) -> Result<hashbrown::HashSet<PathBuf>> {
-    let mut names = hashbrown::HashSet::with_capacity(info_file.exercises.len());
-    let mut paths = hashbrown::HashSet::with_capacity(info_file.exercises.len());
+fn check_info_file_exercises(info_file: &InfoFile) -> Result<HashSet<PathBuf>> {
+    let mut names = hash_set_with_capacity(info_file.exercises.len());
+    let mut paths = hash_set_with_capacity(info_file.exercises.len());
 
     let mut file_buf = String::with_capacity(1 << 14);
     for exercise_info in &info_file.exercises {
@@ -71,7 +72,7 @@ fn check_info_file_exercises(info_file: &InfoFile) -> Result<hashbrown::HashSet<
             }
         }
 
-        if exercise_info.hint.trim().is_empty() {
+        if exercise_info.hint.trim_ascii().is_empty() {
             bail!("The exercise `{name}` has an empty hint. Please provide a hint or at least tell the user why a hint isn't needed for this exercise");
         }
 
@@ -92,6 +93,10 @@ fn check_info_file_exercises(info_file: &InfoFile) -> Result<hashbrown::HashSet<
             bail!("The `main` function is missing in the file `{path}`.\nCreate at least an empty `main` function to avoid language server errors");
         }
 
+        if !file_buf.contains("// TODO") {
+            bail!("Didn't find any `// TODO` comment in the file `{path}`.\nYou need to have at least one such comment to guide the user.");
+        }
+
         if !exercise_info.test && file_buf.contains("#[test]") {
             bail!("The file `{path}` contains tests annotated with `#[test]` but the exercise `{name}` has `test = false` in the `info.toml` file");
         }
@@ -107,10 +112,7 @@ fn check_info_file_exercises(info_file: &InfoFile) -> Result<hashbrown::HashSet<
 // Check `dir` for unexpected files.
 // Only Rust files in `allowed_rust_files` and `README.md` files are allowed.
 // Only one level of directory nesting is allowed.
-fn check_unexpected_files(
-    dir: &str,
-    allowed_rust_files: &hashbrown::HashSet<PathBuf>,
-) -> Result<()> {
+fn check_unexpected_files(dir: &str, allowed_rust_files: &HashSet<PathBuf>) -> Result<()> {
     let unexpected_file = |path: &Path| {
         anyhow!("Found the file `{}`. Only `README.md` and Rust files related to an exercise in `info.toml` are allowed in the `{dir}` directory", path.display())
     };
@@ -158,7 +160,45 @@ fn check_unexpected_files(
     Ok(())
 }
 
-fn check_exercises(info_file: &InfoFile) -> Result<()> {
+fn check_exercises_unsolved(info_file: &InfoFile, cmd_runner: &CmdRunner) -> Result<()> {
+    println!(
+        "Running all exercises to check that they aren't already solved. This may take a while…\n",
+    );
+    thread::scope(|s| {
+        let handles = info_file
+            .exercises
+            .iter()
+            .filter_map(|exercise_info| {
+                if exercise_info.skip_check_unsolved {
+                    return None;
+                }
+
+                Some((
+                    exercise_info.name.as_str(),
+                    s.spawn(|| exercise_info.run_exercise(None, cmd_runner)),
+                ))
+            })
+            .collect::<Vec<_>>();
+
+        for (exercise_name, handle) in handles {
+            let Ok(result) = handle.join() else {
+                bail!("Panic while trying to run the exericse {exercise_name}");
+            };
+
+            match result {
+                Ok(true) => bail!(
+                    "The exercise {exercise_name} is already solved.\n{SKIP_CHECK_UNSOLVED_HINT}",
+                ),
+                Ok(false) => (),
+                Err(e) => return Err(e),
+            }
+        }
+
+        Ok(())
+    })
+}
+
+fn check_exercises(info_file: &InfoFile, cmd_runner: &CmdRunner) -> Result<()> {
     match info_file.format_version.cmp(&CURRENT_FORMAT_VERSION) {
         Ordering::Less => bail!("`format_version` < {CURRENT_FORMAT_VERSION} (supported version)\nPlease migrate to the latest format version"),
         Ordering::Greater => bail!("`format_version` > {CURRENT_FORMAT_VERSION} (supported version)\nTry updating the Rustlings program"),
@@ -166,85 +206,123 @@ fn check_exercises(info_file: &InfoFile) -> Result<()> {
     }
 
     let info_file_paths = check_info_file_exercises(info_file)?;
-    check_unexpected_files("exercises", &info_file_paths)?;
+    let handle = thread::spawn(move || check_unexpected_files("exercises", &info_file_paths));
 
-    Ok(())
+    check_exercises_unsolved(info_file, cmd_runner)?;
+    handle.join().unwrap()
 }
 
-fn check_solutions(require_solutions: bool, info_file: &InfoFile) -> Result<()> {
-    let target_dir = parse_target_dir()?;
-    let paths = Mutex::new(hashbrown::HashSet::with_capacity(info_file.exercises.len()));
-    let error_occurred = AtomicBool::new(false);
+enum SolutionCheck {
+    Success { sol_path: String },
+    MissingRequired,
+    MissingOptional,
+    RunFailure { output: Vec<u8> },
+    Err(Error),
+}
 
-    println!("Running all solutions. This may take a while...\n");
+fn check_solutions(
+    require_solutions: bool,
+    info_file: &InfoFile,
+    cmd_runner: &CmdRunner,
+) -> Result<()> {
+    println!("Running all solutions. This may take a while…\n");
     thread::scope(|s| {
-        for exercise_info in &info_file.exercises {
-            s.spawn(|| {
-                let error = |e| {
-                    let mut stderr = io::stderr().lock();
-                    stderr.write_all(e).unwrap();
-                    stderr
-                        .write_all(b"\nFailed to run the solution of the exercise ")
-                        .unwrap();
-                    stderr.write_all(exercise_info.name.as_bytes()).unwrap();
-                    stderr.write_all(SEPARATOR).unwrap();
-                    error_occurred.store(true, atomic::Ordering::Relaxed);
-                };
+        let handles = info_file
+            .exercises
+            .iter()
+            .map(|exercise_info| {
+                s.spawn(|| {
+                    let sol_path = exercise_info.sol_path();
+                    if !Path::new(&sol_path).exists() {
+                        if require_solutions {
+                            return SolutionCheck::MissingRequired;
+                        }
 
-                let path = exercise_info.sol_path();
-                if !Path::new(&path).exists() {
-                    if require_solutions {
-                        error(b"Solution missing");
+                        return SolutionCheck::MissingOptional;
                     }
 
-                    // No solution to check.
-                    return;
-                }
-
-                let mut output = Vec::with_capacity(OUTPUT_CAPACITY);
-                match exercise_info.run_solution(&mut output, &target_dir) {
-                    Ok(true) => {
-                        paths.lock().unwrap().insert(PathBuf::from(path));
+                    let mut output = Vec::with_capacity(OUTPUT_CAPACITY);
+                    match exercise_info.run_solution(Some(&mut output), cmd_runner) {
+                        Ok(true) => SolutionCheck::Success { sol_path },
+                        Ok(false) => SolutionCheck::RunFailure { output },
+                        Err(e) => SolutionCheck::Err(e),
                     }
-                    Ok(false) => error(&output),
-                    Err(e) => error(e.to_string().as_bytes()),
+                })
+            })
+            .collect::<Vec<_>>();
+
+        let mut sol_paths = hash_set_with_capacity(info_file.exercises.len());
+        let mut fmt_cmd = Command::new("rustfmt");
+        fmt_cmd
+            .arg("--check")
+            .arg("--edition")
+            .arg("2021")
+            .arg("--color")
+            .arg("always")
+            .stdin(Stdio::null());
+
+        for (exercise_info, handle) in info_file.exercises.iter().zip(handles) {
+            let Ok(check_result) = handle.join() else {
+                bail!(
+                    "Panic while trying to run the solution of the exericse {}",
+                    exercise_info.name,
+                );
+            };
+
+            match check_result {
+                SolutionCheck::Success { sol_path } => {
+                    fmt_cmd.arg(&sol_path);
+                    sol_paths.insert(PathBuf::from(sol_path));
                 }
-            });
+                SolutionCheck::MissingRequired => {
+                    bail!(
+                        "The solution of the exercise {} is missing",
+                        exercise_info.name,
+                    );
+                }
+                SolutionCheck::MissingOptional => (),
+                SolutionCheck::RunFailure { output } => {
+                    io::stderr().lock().write_all(&output)?;
+                    bail!(
+                        "Running the solution of the exercise {} failed with the error above",
+                        exercise_info.name,
+                    );
+                }
+                SolutionCheck::Err(e) => return Err(e),
+            }
         }
-    });
 
-    if error_occurred.load(atomic::Ordering::Relaxed) {
-        bail!("At least one solution failed. See the output above.");
-    }
+        let handle = s.spawn(move || check_unexpected_files("solutions", &sol_paths));
 
-    check_unexpected_files("solutions", &paths.into_inner().unwrap())?;
+        if !fmt_cmd
+            .status()
+            .context("Failed to run `rustfmt` on all solution files")?
+            .success()
+        {
+            bail!("Some solutions aren't formatted. Run `rustfmt` on them");
+        }
 
-    Ok(())
+        handle.join().unwrap()
+    })
 }
 
 pub fn check(require_solutions: bool) -> Result<()> {
     let info_file = InfoFile::parse()?;
 
-    // A hack to make `cargo run -- dev check` work when developing Rustlings.
-    if DEBUG_PROFILE {
-        check_cargo_toml(
-            &info_file.exercises,
-            include_str!("../../dev-Cargo.toml"),
-            b"../",
-        )?;
+    if cfg!(debug_assertions) {
+        // A hack to make `cargo run -- dev check` work when developing Rustlings.
+        check_cargo_toml(&info_file.exercises, "dev/Cargo.toml", b"../")?;
     } else {
-        let current_cargo_toml =
-            fs::read_to_string("Cargo.toml").context("Failed to read the file `Cargo.toml`")?;
-        check_cargo_toml(&info_file.exercises, &current_cargo_toml, b"")?;
+        check_cargo_toml(&info_file.exercises, "Cargo.toml", b"")?;
     }
 
-    check_exercises(&info_file)?;
-    check_solutions(require_solutions, &info_file)?;
+    let cmd_runner = CmdRunner::build()?;
+    check_exercises(&info_file, &cmd_runner)?;
+    check_solutions(require_solutions, &info_file, &cmd_runner)?;
 
-    println!("\nEverything looks fine!");
+    println!("Everything looks fine!");
 
     Ok(())
 }
 
-const SEPARATOR: &[u8] =
-    b"\n========================================================================================\n";
+const SKIP_CHECK_UNSOLVED_HINT: &str = "If this is an introduction exercise that is intended to be already solved, add `skip_check_unsolved = true` to the exercise's metadata in the `info.toml` file";

src/dev/new.rs

@@ -76,8 +76,8 @@ pub fn new(path: &Path, no_git: bool) -> Result<()> {
 
 pub const GITIGNORE: &[u8] = b".rustlings-state.txt
 Cargo.lock
-target
-.vscode
+target/
+.vscode/
 !.vscode/extensions.json
 ";
 
@@ -139,7 +139,7 @@ const README: &str = "# Rustlings 🦀
 
 Welcome to these third-party Rustlings exercises 😃
 
-First, [install Rustlings using the official instructions in the README of the Rustlings project](https://github.com/rust-lang/rustlings) ✅
+First, [install Rustlings using the official instructions](https://github.com/rust-lang/rustlings) ✅
 
-Then, open your terminal in this directory and run `rustlings` to get started with the exercises 🚀
+Then, clone this repository, open a terminal in this directory and run `rustlings` to get started with the exercises 🚀
 ";

src/dev/update.rs

@@ -4,18 +4,19 @@ use std::fs;
 use crate::{
     cargo_toml::updated_cargo_toml,
     info_file::{ExerciseInfo, InfoFile},
-    DEBUG_PROFILE,
 };
 
 // Update the `Cargo.toml` file.
 fn update_cargo_toml(
     exercise_infos: &[ExerciseInfo],
-    current_cargo_toml: &str,
-    exercise_path_prefix: &[u8],
     cargo_toml_path: &str,
+    exercise_path_prefix: &[u8],
 ) -> Result<()> {
+    let current_cargo_toml = fs::read_to_string(cargo_toml_path)
+        .with_context(|| format!("Failed to read the file `{cargo_toml_path}`"))?;
+
     let updated_cargo_toml =
-        updated_cargo_toml(exercise_infos, current_cargo_toml, exercise_path_prefix)?;
+        updated_cargo_toml(exercise_infos, &current_cargo_toml, exercise_path_prefix)?;
 
     fs::write(cargo_toml_path, updated_cargo_toml)
         .context("Failed to write the `Cargo.toml` file")?;
@@ -26,21 +27,14 @@ fn update_cargo_toml(
 pub fn update() -> Result<()> {
     let info_file = InfoFile::parse()?;
 
-    // A hack to make `cargo run -- dev update` work when developing Rustlings.
-    if DEBUG_PROFILE {
-        update_cargo_toml(
-            &info_file.exercises,
-            include_str!("../../dev-Cargo.toml"),
-            b"../",
-            "dev/Cargo.toml",
-        )
-        .context("Failed to update the file `dev/Cargo.toml`")?;
+    if cfg!(debug_assertions) {
+        // A hack to make `cargo run -- dev update` work when developing Rustlings.
+        update_cargo_toml(&info_file.exercises, "dev/Cargo.toml", b"../")
+            .context("Failed to update the file `dev/Cargo.toml`")?;
 
         println!("Updated `dev/Cargo.toml`");
     } else {
-        let current_cargo_toml =
-            fs::read_to_string("Cargo.toml").context("Failed to read the file `Cargo.toml`")?;
-        update_cargo_toml(&info_file.exercises, &current_cargo_toml, b"", "Cargo.toml")
+        update_cargo_toml(&info_file.exercises, "Cargo.toml", &[])
             .context("Failed to update the file `Cargo.toml`")?;
 
         println!("Updated `Cargo.toml`");

src/exercise.rs

@@ -1,46 +1,41 @@
 use anyhow::Result;
-use crossterm::style::{style, StyledContent, Stylize};
+use ratatui::crossterm::style::{style, StyledContent, Stylize};
 use std::{
     fmt::{self, Display, Formatter},
     io::Write,
-    path::{Path, PathBuf},
-    process::Command,
 };
 
-use crate::{
-    cmd::{run_cmd, CargoCmd},
-    in_official_repo,
-    terminal_link::TerminalFileLink,
-    DEBUG_PROFILE,
-};
+use crate::{cmd::CmdRunner, terminal_link::TerminalFileLink};
 
 /// The initial capacity of the output buffer.
 pub const OUTPUT_CAPACITY: usize = 1 << 14;
 
 // Run an exercise binary and append its output to the `output` buffer.
 // Compilation must be done before calling this method.
-fn run_bin(bin_name: &str, output: &mut Vec<u8>, target_dir: &Path) -> Result<bool> {
-    writeln!(output, "{}", "Output".underlined())?;
+fn run_bin(
+    bin_name: &str,
+    mut output: Option<&mut Vec<u8>>,
+    cmd_runner: &CmdRunner,
+) -> Result<bool> {
+    if let Some(output) = output.as_deref_mut() {
+        writeln!(output, "{}", "Output".underlined())?;
+    }
 
-    // 7 = "/debug/".len()
-    let mut bin_path = PathBuf::with_capacity(target_dir.as_os_str().len() + 7 + bin_name.len());
-    bin_path.push(target_dir);
-    bin_path.push("debug");
-    bin_path.push(bin_name);
+    let success = cmd_runner.run_debug_bin(bin_name, output.as_deref_mut())?;
 
-    let success = run_cmd(Command::new(&bin_path), &bin_path.to_string_lossy(), output)?;
-
-    if !success {
-        // This output is important to show the user that something went wrong.
-        // Otherwise, calling something like `exit(1)` in an exercise without further output
-        // leaves the user confused about why the exercise isn't done yet.
-        writeln!(
-            output,
-            "{}",
-            "The exercise didn't run successfully (nonzero exit code)"
-                .bold()
-                .red(),
-        )?;
+    if let Some(output) = output {
+        if !success {
+            // This output is important to show the user that something went wrong.
+            // Otherwise, calling something like `exit(1)` in an exercise without further output
+            // leaves the user confused about why the exercise isn't done yet.
+            writeln!(
+                output,
+                "{}",
+                "The exercise didn't run successfully (nonzero exit code)"
+                    .bold()
+                    .red(),
+            )?;
+        }
     }
 
     Ok(success)
@@ -54,7 +49,7 @@ pub struct Exercise {
     pub path: &'static str,
     pub test: bool,
     pub strict_clippy: bool,
-    pub hint: String,
+    pub hint: &'static str,
     pub done: bool,
 }
 
@@ -77,89 +72,77 @@ pub trait RunnableExercise {
 
     // Compile, check and run the exercise or its solution (depending on `bin_name´).
     // The output is written to the `output` buffer after clearing it.
-    fn run(&self, bin_name: &str, output: &mut Vec<u8>, target_dir: &Path) -> Result<bool> {
-        output.clear();
-
-        // Developing the official Rustlings.
-        let dev = DEBUG_PROFILE && in_official_repo();
-
-        let build_success = CargoCmd {
-            subcommand: "build",
-            args: &[],
-            bin_name,
-            description: "cargo build …",
-            hide_warnings: false,
-            target_dir,
-            output,
-            dev,
+    fn run(
+        &self,
+        bin_name: &str,
+        mut output: Option<&mut Vec<u8>>,
+        cmd_runner: &CmdRunner,
+    ) -> Result<bool> {
+        if let Some(output) = output.as_deref_mut() {
+            output.clear();
         }
-        .run()?;
+
+        let build_success = cmd_runner
+            .cargo("build", bin_name, output.as_deref_mut())
+            .run("cargo build …")?;
         if !build_success {
             return Ok(false);
         }
 
-        // Discard the output of `cargo build` because it will be shown again by Clippy.
-        output.clear();
+        // Discard the compiler output because it will be shown again by `cargo test` or Clippy.
+        if let Some(output) = output.as_deref_mut() {
+            output.clear();
+        }
+
+        if self.test() {
+            let output_is_some = output.is_some();
+            let mut test_cmd = cmd_runner.cargo("test", bin_name, output.as_deref_mut());
+            if output_is_some {
+                test_cmd.args(["--", "--color", "always", "--show-output"]);
+            }
+            let test_success = test_cmd.run("cargo test …")?;
+            if !test_success {
+                run_bin(bin_name, output, cmd_runner)?;
+                return Ok(false);
+            }
+
+            // Discard the compiler output because it will be shown again by Clippy.
+            if let Some(output) = output.as_deref_mut() {
+                output.clear();
+            }
+        }
+
+        let mut clippy_cmd = cmd_runner.cargo("clippy", bin_name, output.as_deref_mut());
 
         // `--profile test` is required to also check code with `[cfg(test)]`.
-        let clippy_args: &[&str] = if self.strict_clippy() {
-            &["--profile", "test", "--", "-D", "warnings"]
+        if self.strict_clippy() {
+            clippy_cmd.args(["--profile", "test", "--", "-D", "warnings"]);
         } else {
-            &["--profile", "test"]
-        };
-        let clippy_success = CargoCmd {
-            subcommand: "clippy",
-            args: clippy_args,
-            bin_name,
-            description: "cargo clippy …",
-            hide_warnings: false,
-            target_dir,
-            output,
-            dev,
-        }
-        .run()?;
-        if !clippy_success {
-            return Ok(false);
+            clippy_cmd.args(["--profile", "test"]);
         }
 
-        if !self.test() {
-            return run_bin(bin_name, output, target_dir);
-        }
+        let clippy_success = clippy_cmd.run("cargo clippy …")?;
+        let run_success = run_bin(bin_name, output, cmd_runner)?;
 
-        let test_success = CargoCmd {
-            subcommand: "test",
-            args: &["--", "--color", "always", "--show-output"],
-            bin_name,
-            description: "cargo test …",
-            // Hide warnings because they are shown by Clippy.
-            hide_warnings: true,
-            target_dir,
-            output,
-            dev,
-        }
-        .run()?;
-
-        let run_success = run_bin(bin_name, output, target_dir)?;
-
-        Ok(test_success && run_success)
+        Ok(clippy_success && run_success)
     }
 
     /// Compile, check and run the exercise.
     /// The output is written to the `output` buffer after clearing it.
     #[inline]
-    fn run_exercise(&self, output: &mut Vec<u8>, target_dir: &Path) -> Result<bool> {
-        self.run(self.name(), output, target_dir)
+    fn run_exercise(&self, output: Option<&mut Vec<u8>>, cmd_runner: &CmdRunner) -> Result<bool> {
+        self.run(self.name(), output, cmd_runner)
     }
 
     /// Compile, check and run the exercise's solution.
     /// The output is written to the `output` buffer after clearing it.
-    fn run_solution(&self, output: &mut Vec<u8>, target_dir: &Path) -> Result<bool> {
+    fn run_solution(&self, output: Option<&mut Vec<u8>>, cmd_runner: &CmdRunner) -> Result<bool> {
         let name = self.name();
-        let mut bin_name = String::with_capacity(name.len());
+        let mut bin_name = String::with_capacity(name.len() + 4);
         bin_name.push_str(name);
         bin_name.push_str("_sol");
 
-        self.run(&bin_name, output, target_dir)
+        self.run(&bin_name, output, cmd_runner)
     }
 }
 

src/info_file.rs

@@ -11,14 +11,17 @@ pub struct ExerciseInfo {
     pub name: String,
     /// Exercise's directory name inside the `exercises/` directory.
     pub dir: Option<String>,
-    #[serde(default = "default_true")]
     /// Run `cargo test` on the exercise.
+    #[serde(default = "default_true")]
     pub test: bool,
     /// Deny all Clippy warnings.
     #[serde(default)]
     pub strict_clippy: bool,
     /// The exercise's hint to be shown to the user on request.
     pub hint: String,
+    /// The exercise is already solved. Ignore it when checking that all exercises are unsolved.
+    #[serde(default)]
+    pub skip_check_unsolved: bool,
 }
 #[inline(always)]
 const fn default_true() -> bool {

src/init.rs

@@ -1,32 +1,91 @@
 use anyhow::{bail, Context, Result};
-use crossterm::style::Stylize;
+use ratatui::crossterm::style::Stylize;
+use serde::Deserialize;
 use std::{
     env::set_current_dir,
     fs::{self, create_dir},
-    io::ErrorKind,
-    path::Path,
+    io::{self, Write},
+    path::{Path, PathBuf},
     process::{Command, Stdio},
 };
 
-use crate::{cargo_toml::updated_cargo_toml, embedded::EMBEDDED_FILES, info_file::InfoFile};
+use crate::{
+    cargo_toml::updated_cargo_toml, embedded::EMBEDDED_FILES, info_file::InfoFile,
+    term::press_enter_prompt,
+};
+
+#[derive(Deserialize)]
+struct CargoLocateProject {
+    root: PathBuf,
+}
 
 pub fn init() -> Result<()> {
-    // Prevent initialization in a directory that contains the file `Cargo.toml`.
-    // This can mean that Rustlings was already initialized in this directory.
-    // Otherwise, this can cause problems with Cargo workspaces.
-    if Path::new("Cargo.toml").exists() {
-        bail!(CARGO_TOML_EXISTS_ERR);
+    let rustlings_dir = Path::new("rustlings");
+    if rustlings_dir.exists() {
+        bail!(RUSTLINGS_DIR_ALREADY_EXISTS_ERR);
     }
 
-    let rustlings_path = Path::new("rustlings");
-    if let Err(e) = create_dir(rustlings_path) {
-        if e.kind() == ErrorKind::AlreadyExists {
-            bail!(RUSTLINGS_DIR_ALREADY_EXISTS_ERR);
+    let locate_project_output = Command::new("cargo")
+        .arg("locate-project")
+        .arg("-q")
+        .arg("--workspace")
+        .stdin(Stdio::null())
+        .stderr(Stdio::null())
+        .output()
+        .context(CARGO_LOCATE_PROJECT_ERR)?;
+
+    let mut stdout = io::stdout().lock();
+    let mut init_git = true;
+
+    if locate_project_output.status.success() {
+        if Path::new("exercises").exists() && Path::new("solutions").exists() {
+            bail!(IN_INITIALIZED_DIR_ERR);
         }
-        return Err(e.into());
+
+        let workspace_manifest =
+            serde_json::de::from_slice::<CargoLocateProject>(&locate_project_output.stdout)
+                .context(
+                    "Failed to read the field `root` from the output of `cargo locate-project …`",
+                )?
+                .root;
+
+        let workspace_manifest_content = fs::read_to_string(&workspace_manifest)
+            .with_context(|| format!("Failed to read the file {}", workspace_manifest.display()))?;
+        if !workspace_manifest_content.contains("[workspace]\n")
+            && !workspace_manifest_content.contains("workspace.")
+        {
+            bail!("The current directory is already part of a Cargo project.\nPlease initialize Rustlings in a different directory");
+        }
+
+        stdout.write_all(b"This command will create the directory `rustlings/` as a member of this Cargo workspace.\nPress ENTER to continue ")?;
+        press_enter_prompt(&mut stdout)?;
+
+        // Make sure "rustlings" is added to `workspace.members` by making
+        // Cargo initialize a new project.
+        let status = Command::new("cargo")
+            .arg("new")
+            .arg("-q")
+            .arg("--vcs")
+            .arg("none")
+            .arg("rustlings")
+            .stdin(Stdio::null())
+            .stdout(Stdio::null())
+            .status()?;
+        if !status.success() {
+            bail!("Failed to initialize a new Cargo workspace member.\nPlease initialize Rustlings in a different directory");
+        }
+
+        stdout.write_all(b"The directory `rustlings` has been added to `workspace.members` in the `Cargo.toml` file of this Cargo workspace.\n")?;
+        fs::remove_dir_all("rustlings")
+            .context("Failed to remove the temporary directory `rustlings/`")?;
+        init_git = false;
+    } else {
+        stdout.write_all(b"This command will create the directory `rustlings/` which will contain the exercises.\nPress ENTER to continue ")?;
+        press_enter_prompt(&mut stdout)?;
     }
 
-    set_current_dir("rustlings")
+    create_dir(rustlings_dir).context("Failed to create the `rustlings/` directory")?;
+    set_current_dir(rustlings_dir)
         .context("Failed to change the current directory to `rustlings/`")?;
 
     let info_file = InfoFile::parse()?;
@@ -35,6 +94,11 @@ pub fn init() -> Result<()> {
         .context("Failed to initialize the `rustlings/exercises` directory")?;
 
     create_dir("solutions").context("Failed to create the `solutions/` directory")?;
+    fs::write(
+        "solutions/README.md",
+        include_bytes!("../solutions/README.md"),
+    )
+    .context("Failed to create the file rustlings/solutions/README.md")?;
     for dir in EMBEDDED_FILES.exercise_dirs {
         let mut dir_path = String::with_capacity(10 + dir.name.len());
         dir_path.push_str("solutions/");
@@ -70,41 +134,46 @@ pub fn init() -> Result<()> {
     fs::write(".vscode/extensions.json", VS_CODE_EXTENSIONS_JSON)
         .context("Failed to create the file `rustlings/.vscode/extensions.json`")?;
 
-    // Ignore any Git error because Git initialization is not required.
-    let _ = Command::new("git")
-        .arg("init")
-        .stdin(Stdio::null())
-        .stderr(Stdio::null())
-        .status();
+    if init_git {
+        // Ignore any Git error because Git initialization is not required.
+        let _ = Command::new("git")
+            .arg("init")
+            .stdin(Stdio::null())
+            .stderr(Stdio::null())
+            .status();
+    }
 
-    println!(
+    writeln!(
+        stdout,
         "\n{}\n\n{}",
         "Initialization done ✓".green(),
         POST_INIT_MSG.bold(),
-    );
+    )?;
 
     Ok(())
 }
 
+const CARGO_LOCATE_PROJECT_ERR: &str = "Failed to run the command `cargo locate-project …`
+Did you already install Rust?
+Try running `cargo --version` to diagnose the problem.";
+
 const INIT_SOLUTION_FILE: &[u8] = b"fn main() {
     // DON'T EDIT THIS SOLUTION FILE!
     // It will be automatically filled after you finish the exercise.
 }
 ";
 
-const GITIGNORE: &[u8] = b".rustlings-state.txt
-solutions
-Cargo.lock
-target
-.vscode
+const GITIGNORE: &[u8] = b"Cargo.lock
+target/
+.vscode/
 ";
 
 pub const VS_CODE_EXTENSIONS_JSON: &[u8] = br#"{"recommendations":["rust-lang.rust-analyzer"]}"#;
 
-const CARGO_TOML_EXISTS_ERR: &str = "The current directory contains the file `Cargo.toml`.
+const IN_INITIALIZED_DIR_ERR: &str = "It looks like Rustlings is already initialized in this directory.
 
 If you already initialized Rustlings, run the command `rustlings` for instructions on getting started with the exercises.
-Otherwise, please run `rustlings init` again in another directory.";
+Otherwise, please run `rustlings init` again in a different directory.";
 
 const RUSTLINGS_DIR_ALREADY_EXISTS_ERR: &str =
     "A directory with the name `rustlings` already exists in the current directory.

src/list.rs

@@ -1,10 +1,13 @@
 use anyhow::Result;
-use crossterm::{
-    event::{self, Event, KeyCode, KeyEventKind},
-    terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
-    ExecutableCommand,
+use ratatui::{
+    backend::CrosstermBackend,
+    crossterm::{
+        event::{self, Event, KeyCode, KeyEventKind},
+        terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
+        ExecutableCommand,
+    },
+    Terminal,
 };
-use ratatui::{backend::CrosstermBackend, Terminal};
 use std::io;
 
 use crate::app_state::AppState;
@@ -24,7 +27,7 @@ pub fn list(app_state: &mut AppState) -> Result<()> {
     let mut ui_state = UiState::new(app_state);
 
     'outer: loop {
-        terminal.draw(|frame| ui_state.draw(frame).unwrap())?;
+        terminal.try_draw(|frame| ui_state.draw(frame).map_err(io::Error::other))?;
 
         let key = loop {
             match event::read()? {

src/list/state.rs

@@ -161,7 +161,7 @@ impl<'a> UiState<'a> {
     }
 
     pub fn draw(&mut self, frame: &mut Frame) -> Result<()> {
-        let area = frame.size();
+        let area = frame.area();
 
         frame.render_stateful_widget(
             &self.table,

src/main.rs

@@ -2,16 +2,18 @@ use anyhow::{bail, Context, Result};
 use app_state::StateFileStatus;
 use clap::{Parser, Subcommand};
 use std::{
-    io::{self, BufRead, StdoutLock, Write},
+    io::{self, IsTerminal, Write},
     path::Path,
     process::exit,
 };
+use term::{clear_terminal, press_enter_prompt};
 
 use self::{app_state::AppState, dev::DevCommands, info_file::InfoFile, watch::WatchExit};
 
 mod app_state;
 mod cargo_toml;
 mod cmd;
+mod collections;
 mod dev;
 mod embedded;
 mod exercise;
@@ -20,35 +22,11 @@ mod init;
 mod list;
 mod progress_bar;
 mod run;
+mod term;
 mod terminal_link;
 mod watch;
 
 const CURRENT_FORMAT_VERSION: u8 = 1;
-const DEBUG_PROFILE: bool = {
-    #[allow(unused_assignments, unused_mut)]
-    let mut debug_profile = false;
-
-    #[cfg(debug_assertions)]
-    {
-        debug_profile = true;
-    }
-
-    debug_profile
-};
-
-// The current directory is the official Rustligns repository.
-fn in_official_repo() -> bool {
-    Path::new("dev/rustlings-repo.txt").exists()
-}
-
-fn clear_terminal(stdout: &mut StdoutLock) -> io::Result<()> {
-    stdout.write_all(b"\x1b[H\x1b[2J\x1b[3J")
-}
-
-fn press_enter_prompt() -> io::Result<()> {
-    io::stdin().lock().read_until(b'\n', &mut Vec::new())?;
-    Ok(())
-}
 
 /// Rustlings is a collection of small exercises to get you used to writing and reading Rust code
 #[derive(Parser)]
@@ -89,24 +67,12 @@ enum Subcommands {
 fn main() -> Result<()> {
     let args = Args::parse();
 
-    if !DEBUG_PROFILE && in_official_repo() {
+    if cfg!(not(debug_assertions)) && Path::new("dev/rustlings-repo.txt").exists() {
         bail!("{OLD_METHOD_ERR}");
     }
 
     match args.command {
         Some(Subcommands::Init) => {
-            if DEBUG_PROFILE {
-                bail!("Disabled in the debug build");
-            }
-
-            {
-                let mut stdout = io::stdout().lock();
-                stdout.write_all(b"This command will create the directory `rustlings/` which will contain the exercises.\nPress ENTER to continue ")?;
-                stdout.flush()?;
-                press_enter_prompt()?;
-                stdout.write_all(b"\n")?;
-            }
-
             return init::init().context("Initialization failed");
         }
         Some(Subcommands::Dev(dev_command)) => return dev_command.run(),
@@ -136,11 +102,12 @@ fn main() -> Result<()> {
                 let mut stdout = io::stdout().lock();
                 clear_terminal(&mut stdout)?;
 
-                let welcome_message = welcome_message.trim();
+                let welcome_message = welcome_message.trim_ascii();
                 write!(stdout, "{welcome_message}\n\nPress ENTER to continue ")?;
-                stdout.flush()?;
-                press_enter_prompt()?;
+                press_enter_prompt(&mut stdout)?;
                 clear_terminal(&mut stdout)?;
+                // Flush to be able to show errors occurring before printing a newline to stdout.
+                stdout.flush()?;
             }
             StateFileStatus::Read => (),
         }
@@ -148,6 +115,10 @@ fn main() -> Result<()> {
 
     match args.command {
         None => {
+            if !io::stdout().is_terminal() {
+                bail!("Unsupported or missing terminal/TTY");
+            }
+
             let notify_exercise_names = if args.manual_run {
                 None
             } else {
@@ -197,9 +168,10 @@ fn main() -> Result<()> {
     Ok(())
 }
 
-const OLD_METHOD_ERR: &str = "You are trying to run Rustlings using the old method before v6.
+const OLD_METHOD_ERR: &str =
+    "You are trying to run Rustlings using the old method before version 6.
 The new method doesn't include cloning the Rustlings' repository.
-Please follow the instructions in the README:
+Please follow the instructions in `README.md`:
 https://github.com/rust-lang/rustlings#getting-started";
 
 const FORMAT_VERSION_HIGHER_ERR: &str =
@@ -216,5 +188,5 @@ const PRE_INIT_MSG: &str = r"
  |_|   \__,_|___/\__|_|_|_| |_|\__, |___/
                                |___/
 
-The `exercises` directory wasn't found in the current directory.
+The `exercises/` directory couldn't be found in the current directory.
 If you are just starting with Rustlings, run the command `rustlings init` to initialize it.";

src/progress_bar.rs

@@ -14,7 +14,7 @@ const PROGRESS_EXCEEDS_MAX_ERR: &str =
 
 /// Terminal progress bar to be used when not using Ratataui.
 pub fn progress_bar(progress: u16, total: u16, line_width: u16) -> Result<String> {
-    use crossterm::style::Stylize;
+    use ratatui::crossterm::style::Stylize;
 
     if progress > total {
         bail!(PROGRESS_EXCEEDS_MAX_ERR);

src/run.rs

@@ -1,5 +1,5 @@
 use anyhow::{bail, Result};
-use crossterm::style::{style, Stylize};
+use ratatui::crossterm::style::{style, Stylize};
 use std::io::{self, Write};
 
 use crate::{
@@ -11,7 +11,7 @@ use crate::{
 pub fn run(app_state: &mut AppState) -> Result<()> {
     let exercise = app_state.current_exercise();
     let mut output = Vec::with_capacity(OUTPUT_CAPACITY);
-    let success = exercise.run_exercise(&mut output, app_state.target_dir())?;
+    let success = exercise.run_exercise(Some(&mut output), app_state.cmd_runner())?;
 
     let mut stdout = io::stdout().lock();
     stdout.write_all(&output)?;

src/term.rs

@@ -0,0 +1,12 @@
+use std::io::{self, BufRead, StdoutLock, Write};
+
+pub fn clear_terminal(stdout: &mut StdoutLock) -> io::Result<()> {
+    stdout.write_all(b"\x1b[H\x1b[2J\x1b[3J")
+}
+
+pub fn press_enter_prompt(stdout: &mut StdoutLock) -> io::Result<()> {
+    stdout.flush()?;
+    io::stdin().lock().read_until(b'\n', &mut Vec::new())?;
+    stdout.write_all(b"\n")?;
+    Ok(())
+}

src/watch.rs

@@ -102,8 +102,7 @@ pub fn watch(
                 watch_state.render()?;
             }
             WatchEvent::NotifyErr(e) => {
-                watch_state.into_writer().write_all(NOTIFY_ERR.as_bytes())?;
-                return Err(Error::from(e));
+                return Err(Error::from(e).context(NOTIFY_ERR));
             }
             WatchEvent::TerminalEventErr(e) => {
                 return Err(Error::from(e).context("Terminal event listener failed"));

src/watch/state.rs

@@ -1,5 +1,5 @@
 use anyhow::Result;
-use crossterm::{
+use ratatui::crossterm::{
     style::{style, Stylize},
     terminal,
 };
@@ -51,10 +51,15 @@ impl<'a> WatchState<'a> {
     pub fn run_current_exercise(&mut self) -> Result<()> {
         self.show_hint = false;
 
+        writeln!(
+            self.writer,
+            "\nChecking the exercise `{}`. Please wait…",
+            self.app_state.current_exercise().name,
+        )?;
         let success = self
             .app_state
             .current_exercise()
-            .run_exercise(&mut self.output, self.app_state.target_dir())?;
+            .run_exercise(Some(&mut self.output), self.app_state.cmd_runner())?;
         if success {
             self.done_status =
                 if let Some(solution_path) = self.app_state.current_solution_path()? {

src/watch/terminal_event.rs

@@ -1,4 +1,4 @@
-use crossterm::event::{self, Event, KeyCode, KeyEventKind, KeyModifiers};
+use ratatui::crossterm::event::{self, Event, KeyCode, KeyEventKind, KeyModifiers};
 use std::sync::mpsc::Sender;
 
 use super::WatchEvent;

tests/fixture/failure/Cargo.toml

@@ -1,20 +0,0 @@
-[package]
-name = "failure"
-edition = "2021"
-publish = false
-
-[[bin]]
-name = "compFailure"
-path = "exercises/compFailure.rs"
-
-[[bin]]
-name = "compNoExercise"
-path = "exercises/compNoExercise.rs"
-
-[[bin]]
-name = "testFailure"
-path = "exercises/testFailure.rs"
-
-[[bin]]
-name = "testNotPassed"
-path = "exercises/testNotPassed.rs"

tests/fixture/failure/exercises/testFailure.rs

@@ -1,6 +0,0 @@
-fn main() {}
-
-#[test]
-fn passing() {
-    asset!(true);
-}

tests/fixture/failure/exercises/testNotPassed.rs

@@ -1,6 +0,0 @@
-fn main() {}
-
-#[test]
-fn not_passing() {
-    assert!(false);
-}

tests/fixture/failure/info.toml

@@ -1,10 +0,0 @@
-format_version = 1
-
-[[exercises]]
-name = "compFailure"
-test = false
-hint = ""
-
-[[exercises]]
-name = "testFailure"
-hint = "Hello!"

tests/fixture/state/Cargo.toml

@@ -1,16 +0,0 @@
-[package]
-name = "state"
-edition = "2021"
-publish = false
-
-[[bin]]
-name = "pending_exercise"
-path = "exercises/pending_exercise.rs"
-
-[[bin]]
-name = "pending_test_exercise"
-path = "exercises/pending_test_exercise.rs"
-
-[[bin]]
-name = "finished_exercise"
-path = "exercises/finished_exercise.rs"

tests/fixture/state/exercises/pending_exercise.rs

@@ -1 +0,0 @@
-fn main() {}

tests/fixture/state/exercises/pending_test_exercise.rs

@@ -1,4 +0,0 @@
-fn main() {}
-
-#[test]
-fn it_works() {}

tests/fixture/state/info.toml

@@ -1,15 +0,0 @@
-format_version = 1
-
-[[exercises]]
-name = "pending_exercise"
-test = false
-hint = """"""
-
-[[exercises]]
-name = "pending_test_exercise"
-hint = """"""
-
-[[exercises]]
-name = "finished_exercise"
-test = false
-hint = """"""

tests/fixture/success/Cargo.toml

@@ -1,12 +0,0 @@
-[package]
-name = "success"
-edition = "2021"
-publish = false
-
-[[bin]]
-name = "compSuccess"
-path = "exercises/compSuccess.rs"
-
-[[bin]]
-name = "testSuccess"
-path = "exercises/testSuccess.rs"

tests/fixture/success/exercises/compSuccess.rs

@@ -1 +0,0 @@
-fn main() {}

tests/fixture/success/exercises/testSuccess.rs

@@ -1,7 +0,0 @@
-fn main() {}
-
-#[test]
-fn passing() {
-    println!("THIS TEST TOO SHALL PASS");
-    assert!(true);
-}

tests/fixture/success/info.toml

@@ -1,10 +0,0 @@
-format_version = 1
-
-[[exercises]]
-name = "compSuccess"
-test = false
-hint = """"""
-
-[[exercises]]
-name = "testSuccess"
-hint = """"""

tests/integration_tests.rs

@@ -1,134 +1,182 @@
-use assert_cmd::prelude::*;
-use std::process::Command;
+use std::{
+    env::{self, consts::EXE_SUFFIX},
+    process::{Command, Stdio},
+    str::from_utf8,
+};
 
-#[test]
-fn fails_when_in_wrong_dir() {
-    Command::cargo_bin("rustlings")
-        .unwrap()
-        .current_dir("tests/")
-        .assert()
-        .code(1);
+enum Output<'a> {
+    FullStdout(&'a str),
+    PartialStdout(&'a str),
+    PartialStderr(&'a str),
+}
+
+use Output::*;
+
+#[derive(Default)]
+struct Cmd<'a> {
+    current_dir: Option<&'a str>,
+    args: &'a [&'a str],
+    output: Option<Output<'a>>,
+}
+
+impl<'a> Cmd<'a> {
+    #[inline]
+    fn current_dir(&mut self, current_dir: &'a str) -> &mut Self {
+        self.current_dir = Some(current_dir);
+        self
+    }
+
+    #[inline]
+    fn args(&mut self, args: &'a [&'a str]) -> &mut Self {
+        self.args = args;
+        self
+    }
+
+    #[inline]
+    fn output(&mut self, output: Output<'a>) -> &mut Self {
+        self.output = Some(output);
+        self
+    }
+
+    fn assert(&self, success: bool) {
+        let rustlings_bin = {
+            let mut path = env::current_exe().unwrap();
+            // Pop test binary name
+            path.pop();
+            // Pop `/deps`
+            path.pop();
+
+            path.push("rustlings");
+            let mut path = path.into_os_string();
+            path.push(EXE_SUFFIX);
+            path
+        };
+
+        let mut cmd = Command::new(rustlings_bin);
+
+        if let Some(current_dir) = self.current_dir {
+            cmd.current_dir(current_dir);
+        }
+
+        cmd.args(self.args).stdin(Stdio::null());
+
+        let status = match self.output {
+            None => cmd
+                .stdout(Stdio::null())
+                .stderr(Stdio::null())
+                .status()
+                .unwrap(),
+            Some(FullStdout(stdout)) => {
+                let output = cmd.stderr(Stdio::null()).output().unwrap();
+                assert_eq!(from_utf8(&output.stdout).unwrap(), stdout);
+                output.status
+            }
+            Some(PartialStdout(stdout)) => {
+                let output = cmd.stderr(Stdio::null()).output().unwrap();
+                assert!(from_utf8(&output.stdout).unwrap().contains(stdout));
+                output.status
+            }
+            Some(PartialStderr(stderr)) => {
+                let output = cmd.stdout(Stdio::null()).output().unwrap();
+                assert!(from_utf8(&output.stderr).unwrap().contains(stderr));
+                output.status
+            }
+        };
+
+        assert_eq!(status.success(), success, "{cmd:?}");
+    }
+
+    #[inline]
+    fn success(&self) {
+        self.assert(true);
+    }
+
+    #[inline]
+    fn fail(&self) {
+        self.assert(false);
+    }
 }
 
 #[test]
-fn run_single_compile_success() {
-    Command::cargo_bin("rustlings")
-        .unwrap()
-        .args(["run", "compSuccess"])
-        .current_dir("tests/fixture/success/")
-        .assert()
+fn run_compilation_success() {
+    Cmd::default()
+        .current_dir("tests/test_exercises")
+        .args(&["run", "compilation_success"])
         .success();
 }
 
 #[test]
-fn run_single_compile_failure() {
-    Command::cargo_bin("rustlings")
-        .unwrap()
-        .args(["run", "compFailure"])
-        .current_dir("tests/fixture/failure/")
-        .assert()
-        .code(1);
+fn run_compilation_failure() {
+    Cmd::default()
+        .current_dir("tests/test_exercises")
+        .args(&["run", "compilation_failure"])
+        .fail();
 }
 
 #[test]
-fn run_single_test_success() {
-    Command::cargo_bin("rustlings")
-        .unwrap()
-        .args(["run", "testSuccess"])
-        .current_dir("tests/fixture/success/")
-        .assert()
+fn run_test_success() {
+    Cmd::default()
+        .current_dir("tests/test_exercises")
+        .args(&["run", "test_success"])
+        .output(PartialStdout("\nOutput from `main` function\n"))
         .success();
 }
 
 #[test]
-fn run_single_test_failure() {
-    Command::cargo_bin("rustlings")
-        .unwrap()
-        .args(["run", "testFailure"])
-        .current_dir("tests/fixture/failure/")
-        .assert()
-        .code(1);
+fn run_test_failure() {
+    Cmd::default()
+        .current_dir("tests/test_exercises")
+        .args(&["run", "test_failure"])
+        .fail();
 }
 
 #[test]
-fn run_single_test_not_passed() {
-    Command::cargo_bin("rustlings")
-        .unwrap()
-        .args(["run", "testNotPassed.rs"])
-        .current_dir("tests/fixture/failure/")
-        .assert()
-        .code(1);
+fn run_exercise_not_in_info() {
+    Cmd::default()
+        .current_dir("tests/test_exercises")
+        .args(&["run", "not_in_info"])
+        .fail();
 }
 
 #[test]
-fn run_single_test_no_exercise() {
-    Command::cargo_bin("rustlings")
-        .unwrap()
-        .args(["run", "compNoExercise.rs"])
-        .current_dir("tests/fixture/failure")
-        .assert()
-        .code(1);
+fn reset_without_exercise_name() {
+    Cmd::default().args(&["reset"]).fail();
 }
 
 #[test]
-fn reset_single_exercise() {
-    Command::cargo_bin("rustlings")
-        .unwrap()
-        .args(["reset", "intro1"])
-        .assert()
-        .code(0);
+fn hint() {
+    Cmd::default()
+        .current_dir("tests/test_exercises")
+        .args(&["hint", "test_failure"])
+        .output(FullStdout("The answer to everything: 42\n"))
+        .success();
 }
 
 #[test]
-fn reset_no_exercise() {
-    Command::cargo_bin("rustlings")
-        .unwrap()
-        .arg("reset")
-        .assert()
-        .code(2)
-        .stderr(predicates::str::contains(
-            "required arguments were not provided",
-        ));
-}
+fn init() {
+    let test_dir = tempfile::TempDir::new().unwrap();
+    let test_dir = test_dir.path().to_str().unwrap();
 
-#[test]
-fn get_hint_for_single_test() {
-    Command::cargo_bin("rustlings")
-        .unwrap()
-        .args(["hint", "testFailure"])
-        .current_dir("tests/fixture/failure")
-        .assert()
-        .code(0)
-        .stdout("Hello!\n");
-}
+    Cmd::default().current_dir(test_dir).fail();
 
-#[test]
-fn run_compile_exercise_does_not_prompt() {
-    Command::cargo_bin("rustlings")
-        .unwrap()
-        .args(["run", "pending_exercise"])
-        .current_dir("tests/fixture/state")
-        .assert()
-        .code(0);
-}
+    Cmd::default()
+        .current_dir(test_dir)
+        .args(&["init"])
+        .success();
 
-#[test]
-fn run_test_exercise_does_not_prompt() {
-    Command::cargo_bin("rustlings")
-        .unwrap()
-        .args(["run", "pending_test_exercise"])
-        .current_dir("tests/fixture/state")
-        .assert()
-        .code(0);
-}
+    // Running `init` after a successful initialization.
+    Cmd::default()
+        .current_dir(test_dir)
+        .args(&["init"])
+        .output(PartialStderr("`cd rustlings`"))
+        .fail();
 
-#[test]
-fn run_single_test_success_with_output() {
-    Command::cargo_bin("rustlings")
-        .unwrap()
-        .args(["run", "testSuccess"])
-        .current_dir("tests/fixture/success/")
-        .assert()
-        .code(0)
-        .stdout(predicates::str::contains("THIS TEST TOO SHALL PASS"));
+    let initialized_dir = format!("{test_dir}/rustlings");
+
+    // Running `init` in the initialized directory.
+    Cmd::default()
+        .current_dir(&initialized_dir)
+        .args(&["init"])
+        .output(PartialStderr("already initialized"))
+        .fail();
 }

tests/test_exercises/dev/Cargo.toml

@@ -0,0 +1,11 @@
+bin = [
+  { name = "compilation_success", path = "../exercises/compilation_success.rs" },
+  { name = "compilation_failure", path = "../exercises/compilation_failure.rs" },
+  { name = "test_success", path = "../exercises/test_success.rs" },
+  { name = "test_failure", path = "../exercises/test_failure.rs" },
+]
+
+[package]
+name = "test_exercises"
+edition = "2021"
+publish = false

tests/test_exercises/exercises/test_failure.rs

@@ -0,0 +1,9 @@
+fn main() {}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn fails() {
+        assert!(false);
+    }
+}

tests/test_exercises/exercises/test_success.rs

@@ -0,0 +1,9 @@
+fn main() {
+    println!("Output from `main` function");
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn passes() {}
+}

tests/test_exercises/info.toml

@@ -0,0 +1,19 @@
+format_version = 1
+
+[[exercises]]
+name = "compilation_success"
+test = false
+hint = ""
+
+[[exercises]]
+name = "compilation_failure"
+test = false
+hint = ""
+
+[[exercises]]
+name = "test_success"
+hint = ""
+
+[[exercises]]
+name = "test_failure"
+hint = "The answer to everything: 42"