Test warning about unexpected nextest exit codes

Should fix a coverage gap in src/cargo.rs

Author: sourcefrog

src/cargo.rs

@@ -24,8 +24,8 @@ use crate::Result;
 
 // Allowed nextest codes (those will be considered a mutation caught / ignored without a warning)
 const NEXTEST_ALLOWED_CODES: &[i32] = &[
-    NextestExitCode::TEST_RUN_FAILED,
     NextestExitCode::NO_TESTS_RUN,
+    NextestExitCode::TEST_RUN_FAILED,
     NextestExitCode::BUILD_FAILED,
 ];
 

tests/nextest.rs

@@ -1,8 +1,11 @@
-// Copyright 2024 Martin Pool
+// Copyright 2024-2025 Martin Pool
 
 //! Integration tests for cargo mutants calling nextest.
 
+use std::fs::{create_dir, write};
+
 use predicates::prelude::*;
+use tempfile::TempDir;
 
 mod util;
 use util::{copy_of_testdata, run};
@@ -27,3 +30,57 @@ fn test_with_nextest_on_small_tree() {
         String::from_utf8_lossy(&assert.get_output().stdout)
     );
 }
+
+#[test]
+fn unexpected_nextest_error_code_causes_a_warning() {
+    let temp = TempDir::new().unwrap();
+    let path = temp.path();
+    write(
+        path.join("Cargo.toml"),
+        r#"[package]
+            name = "cargo-mutants-test"
+            version = "0.1.0"
+            publish = false
+            "#,
+    )
+    .unwrap();
+    create_dir(path.join("src")).unwrap();
+    write(
+        path.join("src/main.rs"),
+        r#"fn main() {
+        println!("{}", 1 + 2);
+        }"#,
+    )
+    .unwrap();
+    create_dir(path.join(".config")).unwrap();
+    write(
+        path.join(".config/nextest.toml"),
+        r#"nextest-version = { required = "9999.0.0" }"#,
+    )
+    .unwrap();
+
+    let assert = run()
+        .args([
+            "mutants",
+            "--test-tool",
+            "nextest",
+            "-vV",
+            "--no-shuffle",
+            "-Ldebug",
+        ])
+        .arg("-d")
+        .arg(temp.path())
+        .assert()
+        .stderr(predicates::str::contains(
+            "nextest process exited with unexpected code (allowed: [4, 100, 101]) code=92",
+        ))
+        .code(4); // CLEAN_TESTS_FAILED
+    println!(
+        "stdout:\n{}",
+        String::from_utf8_lossy(&assert.get_output().stdout)
+    );
+    println!(
+        "stderr:\n{}",
+        String::from_utf8_lossy(&assert.get_output().stderr)
+    );
+}