add tests

tests/fixture/compNoExercise.rs

@@ -0,0 +1,2 @@
+fn main() {
+}

tests/fixture/compSuccess.rs

@@ -0,0 +1,2 @@
+fn main() {
+}

tests/fixture/info.toml

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+[[exercises]]
+path = "compSuccess.rs"
+mode = "compile"
+
+[[exercises]]
+path = "testSuccess.rs"
+mode = "test"

tests/fixture/testSuccess.rs

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+#[test]
+fn passing() {
+    assert!(true);
+}

tests/integration_tests.rs

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+use std::process::Command;
+use assert_cmd::prelude::*;
+
+#[test]
+fn runs_without_arguments() {
+    let mut cmd = Command::cargo_bin("rustlings").unwrap();
+    cmd.assert().success();
+}
+
+#[test]
+fn fails_when_in_wrong_dir() {
+    Command::cargo_bin("rustlings").unwrap()
+        .current_dir("tests/")
+        .assert()
+        .failure();
+}
+
+#[test]
+fn verify_all_success() {
+    Command::cargo_bin("rustlings").unwrap()
+        .arg("v")
+        .current_dir("tests/fixture/")
+        .assert()
+        .success();
+}
+
+#[test]
+fn run_single_compile_success() {
+    Command::cargo_bin("rustlings").unwrap()
+        .args(&["r", "compSuccess.rs"])
+        .current_dir("tests/fixture/")
+        .assert()
+        .success();
+}
+
+#[test]
+fn run_single_test_success() {
+    Command::cargo_bin("rustlings").unwrap()
+        .args(&["r", "testSuccess.rs"])
+        .current_dir("tests/fixture/")
+        .assert()
+        .success();
+}
+
+#[test]
+fn run_single_test_no_filename() {
+    Command::cargo_bin("rustlings").unwrap()
+        .arg("r")
+        .current_dir("tests/fixture/")
+        .assert()
+        .failure();
+}
+
+#[test]
+fn run_single_test_no_exercise() {
+    Command::cargo_bin("rustlings").unwrap()
+        .args(&["r", "compNoExercise.rs"])
+        .current_dir("tests/fixture/")
+        .assert()
+        .failure();
+}