Test error values

.vscode/settings.json

@@ -1,3 +1 @@
-{
-  "rust-analyzer.linkedProjects": ["./testdata/tree/error_handling/Cargo.toml"]
-}
+{}

Cargo.toml

@@ -89,7 +89,7 @@ exclude = [
     "testdata/tree/cfg_attr_mutants_skip",
     "testdata/tree/cfg_attr_test_skip",
     "testdata/tree/dependency",
-    "testdata/tree/error_handling",
+    "testdata/tree/error_value",
     "testdata/tree/everything_skipped",
     "testdata/tree/factorial",
     "testdata/tree/fails_without_feature",

testdata/tree/error_value/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "cargo-mutants-testdata-error-value"
+version = "0.0.0"
+edition = "2021"
+authors = ["Martin Pool"]
+publish = false
+
+[lib]
+doctest = false

testdata/tree/error_handling/README.md → testdata/tree/error_value/README.md

@@ -1,4 +1,4 @@
-# `error_handling` tree
+# `error_value` tree
 
 This tree contains a function that can return an error.
 The tests ignore the error case, so would fail to detect

tests/cli/main.rs

@@ -851,6 +851,26 @@ fn small_well_tested_mutants_with_cargo_arg_release() {
         .unwrap();
 }
 
+#[test]
+fn error_value_catches_untested_ok_case() {
+    // By default this tree should fail because it's configured to
+    // generate an error value, and the tests forgot to check that
+    // the code under test does return Ok.
+    let tmp_src_dir = copy_of_testdata("error_value");
+    run()
+        .arg("mutants")
+        .args(["-v", "-V", "--no-times", "--no-shuffle"])
+        .arg("-d")
+        .arg(tmp_src_dir.path())
+        .assert()
+        .code(2)
+        .stderr("")
+        .stdout(predicate::function(|stdout| {
+            insta::assert_snapshot!(stdout);
+            true
+        }));
+}
+
 #[test]
 /// The `--output` directory creates the named directory if necessary, and then
 /// creates `mutants.out` within it. `mutants.out` is not created in the

tests/cli/snapshots/cli__error_value_catches_untested_ok_case.snap

@@ -0,0 +1,10 @@
+---
+source: tests/cli/main.rs
+expression: stdout
+---
+Found 2 mutants to test
+Unmutated baseline ... ok
+src/lib.rs:3: replace even_is_ok -> Result<u32, &'static str> with Ok(Default::default()) ... caught
+src/lib.rs:3: replace even_is_ok -> Result<u32, &'static str> with Err("injected") ... NOT CAUGHT
+2 mutants tested: 1 missed, 1 caught
+

tests/cli/snapshots/cli__list_mutants_in_all_trees_as_json.snap

@@ -98,20 +98,20 @@ expression: buf
 ]
 ```
 
-## testdata/tree/error_handling
+## testdata/tree/error_value
 
 ```json
 [
   {
-    "package": "cargo-mutants-testdata-small-well-tested",
+    "package": "cargo-mutants-testdata-error-value",
     "file": "src/lib.rs",
     "line": 3,
     "function": "even_is_ok",
     "return_type": "-> Result<u32, &'static str>",
     "replacement": "Ok(Default::default())"
   },
   {
-    "package": "cargo-mutants-testdata-small-well-tested",
+    "package": "cargo-mutants-testdata-error-value",
     "file": "src/lib.rs",
     "line": 3,
     "function": "even_is_ok",

tests/cli/snapshots/cli__list_mutants_in_all_trees_as_text.snap

@@ -43,7 +43,7 @@ src/lib.rs:17: replace double -> usize with Default::default()
 src/lib.rs:1: replace factorial -> u32 with Default::default()
 ```
 
-## testdata/tree/error_handling
+## testdata/tree/error_value
 
 ```
 src/lib.rs:3: replace even_is_ok -> Result<u32, &'static str> with Ok(Default::default())