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Add slide to show the Mockall crate in action (#1532)
As more and more Android teams start using Rust, the question of "How to do mocking?" has come up more frequently. Right now, we don't have a good answer to those teams, AOSP doesn't have any mocking framework available. That will change soon with the import of Mockall and this slide is part of the supporting documentation that we can point teams to.
This commit is contained in:
Martin Geisler
GitHub
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Cargo.lock
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112
Cargo.lock
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@ -468,6 +468,12 @@ dependencies = [
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"syn 1.0.109",
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]
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[[package]]
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name = "difflib"
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version = "0.4.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "6184e33543162437515c2e2b48714794e37845ec9851711914eec9d308f6ebe8"
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[[package]]
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name = "digest"
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version = "0.10.7"
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@ -478,6 +484,12 @@ dependencies = [
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"crypto-common",
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]
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[[package]]
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name = "downcast"
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version = "0.11.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "1435fa1053d8b2fbbe9be7e97eca7f33d37b28409959813daefc1446a14247f1"
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[[package]]
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name = "dtoa"
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version = "1.0.9"
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@ -499,6 +511,12 @@ version = "0.6.2"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "3a68a4904193147e0a8dec3314640e6db742afd5f6e634f428a6af230d9b3591"
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[[package]]
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name = "either"
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version = "1.9.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "a26ae43d7bcc3b814de94796a5e736d4029efb0ee900c12e2d54c993ad1a1e07"
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[[package]]
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name = "elasticlunr-rs"
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version = "3.0.2"
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@ -575,6 +593,15 @@ dependencies = [
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"windows-sys",
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]
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[[package]]
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name = "float-cmp"
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version = "0.9.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "98de4bbd547a563b716d8dfa9aad1cb19bfab00f4fa09a6a4ed21dbcf44ce9c4"
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dependencies = [
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"num-traits",
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]
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[[package]]
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name = "fnv"
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version = "1.0.7"
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@ -605,6 +632,12 @@ dependencies = [
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"percent-encoding",
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]
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[[package]]
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name = "fragile"
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version = "2.0.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "6c2141d6d6c8512188a7891b4b01590a45f6dac67afb4f255c4124dbb86d4eaa"
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[[package]]
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name = "fsevent-sys"
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version = "4.1.0"
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@ -1031,6 +1064,15 @@ dependencies = [
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name = "iterators"
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version = "0.1.0"
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[[package]]
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name = "itertools"
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version = "0.10.5"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "b0fd2260e829bddf4cb6ea802289de2f86d6a7a690192fbe91b3f46e0f2c8473"
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dependencies = [
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"either",
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]
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[[package]]
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name = "itoa"
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version = "1.0.9"
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@ -1258,6 +1300,33 @@ dependencies = [
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"windows-sys",
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]
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[[package]]
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name = "mockall"
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version = "0.11.4"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "4c84490118f2ee2d74570d114f3d0493cbf02790df303d2707606c3e14e07c96"
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dependencies = [
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"cfg-if",
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"downcast",
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"fragile",
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"lazy_static",
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"mockall_derive",
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"predicates",
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"predicates-tree",
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]
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[[package]]
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name = "mockall_derive"
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version = "0.11.4"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "22ce75669015c4f47b289fd4d4f56e894e4c96003ffdf3ac51313126f94c6cbb"
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dependencies = [
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"cfg-if",
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"proc-macro2",
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"quote",
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"syn 1.0.109",
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]
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[[package]]
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name = "native-tls"
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version = "0.2.11"
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@ -1282,6 +1351,12 @@ version = "1.0.4"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "e4a24736216ec316047a1fc4252e27dabb04218aa4a3f37c6e7ddbf1f9782b54"
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[[package]]
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name = "normalize-line-endings"
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version = "0.3.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "61807f77802ff30975e01f4f071c8ba10c022052f98b3294119f3e615d13e5be"
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[[package]]
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name = "normpath"
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version = "1.1.1"
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@ -1617,6 +1692,36 @@ version = "0.1.1"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "925383efa346730478fb4838dbe9137d2a47675ad789c546d150a6e1dd4ab31c"
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[[package]]
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name = "predicates"
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version = "2.1.5"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "59230a63c37f3e18569bdb90e4a89cbf5bf8b06fea0b84e65ea10cc4df47addd"
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dependencies = [
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"difflib",
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"float-cmp",
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"itertools",
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"normalize-line-endings",
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"predicates-core",
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"regex",
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]
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[[package]]
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name = "predicates-core"
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version = "1.0.6"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "b794032607612e7abeb4db69adb4e33590fa6cf1149e95fd7cb00e634b92f174"
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[[package]]
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name = "predicates-tree"
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version = "1.0.9"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "368ba315fb8c5052ab692e68a0eefec6ec57b23a36959c14496f0b0df2c0cecf"
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dependencies = [
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"predicates-core",
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"termtree",
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]
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[[package]]
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name = "pretty_env_logger"
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version = "0.5.0"
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@ -2210,11 +2315,18 @@ dependencies = [
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"windows-sys",
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]
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[[package]]
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name = "termtree"
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version = "0.4.1"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "3369f5ac52d5eb6ab48c6b4ffdc8efbcad6b89c765749064ba298f2c68a16a76"
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[[package]]
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name = "testing"
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version = "0.1.0"
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dependencies = [
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"googletest",
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"mockall",
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]
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[[package]]
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@ -173,6 +173,7 @@
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- [Other Types of Tests](testing/other.md)
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- [Useful Crates](testing/useful-crates.md)
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- [GoogleTest](testing/googletest.md)
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- [Mocking](testing/mocking.md)
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- [Compiler lints and Clippy](testing/lints.md)
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- [Exercise: Luhn Algorithm](testing/exercise.md)
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- [Solution](testing/solution.md)
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@ -10,9 +10,16 @@ crate-type = ["staticlib"]
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path = "googletest.rs"
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test = true
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[[example]]
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name = "mockall-example"
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crate-type = ["staticlib"]
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path = "mockall.rs"
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test = true
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[[bin]]
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name = "luhn"
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path = "exercise.rs"
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[dependencies]
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googletest = "0.10.0"
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mockall = "0.11.4"
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13
src/testing/mockall.rs
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13
src/testing/mockall.rs
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@ -0,0 +1,13 @@
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use std::time::Duration;
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#[mockall::automock]
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pub trait Pet {
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fn is_hungry(&self, since_last_meal: Duration) -> bool;
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}
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#[test]
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fn test_robot_pet() {
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let mut mock_dog = MockPet::new();
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mock_dog.expect_is_hungry().return_const(true);
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assert_eq!(mock_dog.is_hungry(Duration::from_secs(10)), true);
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}
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58
src/testing/mocking.md
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58
src/testing/mocking.md
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@ -0,0 +1,58 @@
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---
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minutes: 5
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---
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# Mocking
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If you want to do mocking, we recommend [Mockall]. You need to refactor your
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code to use traits, which you can then quickly mock:
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```rust,ignore
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{{#include mockall.rs}}
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```
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[Mockall]: https://docs.rs/mockall/
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<details>
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- Note that *mocking is controversial*: mocks allow you to completely isolate a
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test from its dependencies. The immediate result is faster and more stable
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test execution. On the other hand, the mocks can be configured wrongly and
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return output different from what the real dependencies would do.
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If at all possible, it is recommended that you use the real dependencies. As
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an example, many databases allow you to configure an in-memory backend. This
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means that you get the correct behavior in your tests, plus they are fast and
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will automatically clean up after themselves.
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Similarly, many web frameworks allow you to start an in-process server which
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binds to a random port on `localhost`. Always prefer this over mocking away
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the framework since it helps you test your code in the real environment.
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- Mockall is not part of the Rust Playground, so you need to run this example in
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a local environment. Use `cargo add mockall` to quickly add Mockall to an
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existing Cargo project.
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- Mockall has a lot more functionality. In particular, you can set up
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expectations which depend on the arguments passed:
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```rust,ignore
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let mut mock_cat = MockPet::new();
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mock_cat
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.expect_is_hungry()
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.with(mockall::predicate::gt(Duration::from_secs(3 * 3600)))
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.return_const(true);
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mock_cat
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.expect_is_hungry()
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.return_const(true);
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assert_eq!(mock_cat.is_hungry(Duration::from_secs(1 * 3600)), false);
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assert_eq!(mock_cat.is_hungry(Duration::from_secs(5 * 3600)), true);
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```
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- You can use `.times(n)` to limit the number of times a mock method can be
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called to `n` --- the mock will automatically panic when dropped if this isn't
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satisfied.
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- Mockall is available for use in AOSP.
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</details>
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