Bug 1615903 - Add unit tests for rustfmt r=ahal

Differential Revision: https://phabricator.services.mozilla.com/D63028

--HG--
extra : moz-landing-system : lando

tools/lint/test/files/rustfmt/subdir/bad.rs

@@ -0,0 +1,16 @@
+fn main() {
+    // Statements here are executed when the compiled binary is called
+
+    // Print text to the console
+    println!("Hello World!");
+    // Clippy detects this as a swap and considers this as an error
+    let mut a =
+        1;
+    let mut b=1;
+
+    a =
+        b;
+    b = a;
+
+
+}

tools/lint/test/files/rustfmt/subdir/bad2.rs

@@ -0,0 +1,17 @@
+fn main() {
+    // Statements here are executed when the compiled binary is called
+
+    // Print text to the console
+    println!("Hello World!");
+    let mut a;
+    let mut b=1;
+    let mut vec = Vec::new();
+    vec.push(1);
+    vec.push(2);
+
+
+    for x in 5..10 - 5 {
+        a = x;
+    }
+
+    }

tools/lint/test/files/rustfmt/subdir/good.rs

@@ -0,0 +1,6 @@
+fn main() {
+    // Statements here are executed when the compiled binary is called
+
+    // Print text to the console
+    println!("Hello World!");
+}

tools/lint/test/python.ini

@@ -19,3 +19,5 @@ skip-if = os == "win" || os == "mac"  # codespell installed on Linux
 [test_yaml.py]
 [test_clippy.py]
 skip-if = os == "win" || os == "mac"  # only installed on Linux
+[test_rustfmt.py]
+skip-if = os == "win" || os == "mac"  # only installed on Linux

tools/lint/test/test_rustfmt.py

@@ -0,0 +1,44 @@
+import mozunit
+
+
+LINTER = 'rustfmt'
+
+
+def test_good(lint, config, paths):
+    results = lint(paths("subdir/good.rs"))
+    print(results)
+    assert len(results) == 0
+
+
+def test_basic(lint, config, paths):
+    results = lint(paths("subdir/bad.rs"))
+    print(results)
+    assert len(results) >= 1
+
+    assert "Reformat rust" in results[0].message
+    assert results[0].level == "warning"
+    assert results[0].lineno == 4
+    assert "bad.rs" in results[0].path
+    assert "Print text to the console" in results[0].diff
+
+
+def test_dir(lint, config, paths):
+    results = lint(paths("subdir/"))
+    print(results)
+    assert len(results) >= 4
+
+    assert "Reformat rust" in results[0].message
+    assert results[0].level == "warning"
+    assert results[0].lineno == 4
+    assert "bad.rs" in results[0].path
+    assert "Print text to the console" in results[0].diff
+
+    assert "Reformat rust" in results[1].message
+    assert results[1].level == "warning"
+    assert results[1].lineno == 4
+    assert "bad2.rs" in results[1].path
+    assert "Print text to the console" in results[1].diff
+
+
+if __name__ == '__main__':
+    mozunit.main()