feat(cargo-codspeed): add default harness integration test

Author: GuillaumeLagrange

crates/cargo-codspeed/tests/default_harness_error.in/.gitignore

@@ -0,0 +1,2 @@
+target/
+Cargo.lock

crates/cargo-codspeed/tests/default_harness_error.in/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "default-harness-error-test"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]
+bencher = "0.1.5"
+codspeed = { path = "../../../codspeed" }
+codspeed-bencher-compat = { path = "../../../bencher_compat" }
+
+[[bench]]
+name = "bencher_example"
+# Missing harness = false to trigger error
+
+[[bench]]
+name = "bencher_correct"
+harness = false

crates/cargo-codspeed/tests/default_harness_error.in/benches/bencher_correct.rs

@@ -0,0 +1,9 @@
+use codspeed::codspeed::black_box;
+use codspeed_bencher_compat::{benchmark_group, benchmark_main, Bencher};
+
+pub fn b(bench: &mut Bencher) {
+    bench.iter(|| (0..50).fold(0, |x, y| black_box(x + y)))
+}
+
+benchmark_group!(benches, b);
+benchmark_main!(benches);

crates/cargo-codspeed/tests/default_harness_error.in/benches/bencher_example.rs

@@ -0,0 +1,9 @@
+use codspeed::codspeed::black_box;
+use codspeed_bencher_compat::{benchmark_group, benchmark_main, Bencher};
+
+pub fn a(bench: &mut Bencher) {
+    bench.iter(|| (0..100).fold(0, |x, y| black_box(x + y)))
+}
+
+benchmark_group!(benches, a);
+benchmark_main!(benches);

crates/cargo-codspeed/tests/default_harness_error.in/benches/bencher_no_section.rs

@@ -0,0 +1,9 @@
+use codspeed::codspeed::black_box;
+use codspeed_bencher_compat::{benchmark_group, benchmark_main, Bencher};
+
+pub fn c(bench: &mut Bencher) {
+    bench.iter(|| (0..75).fold(0, |x, y| black_box(x + y)))
+}
+
+benchmark_group!(benches, c);
+benchmark_main!(benches);

crates/cargo-codspeed/tests/default_harness_error.rs

@@ -0,0 +1,33 @@
+use predicates::prelude::*;
+use predicates::str::contains;
+
+mod helpers;
+use helpers::*;
+
+const DIR: &str = "tests/default_harness_error.in";
+
+#[test]
+fn test_default_harness_error() {
+    let dir = setup(DIR, Project::DefaultHarnessError);
+    cargo_codspeed(&dir)
+        .arg("build")
+        .assert()
+        .failure()
+        .stderr(contains(
+            "Error: The following benchmark targets use the default test harness:",
+        ))
+        // Should report bencher_example (explicit bench with missing harness = false)
+        .stderr(contains(
+            "`bencher_example` in package `default-harness-error-test`",
+        ))
+        // Should report bencher_no_section (no [[bench]] section means default harness)
+        .stderr(contains(
+            "`bencher_no_section` in package `default-harness-error-test`",
+        ))
+        .stderr(contains(
+            "Codspeed requires benchmark targets to disable the default test harness.",
+        ))
+        // Ensure the correct benchmark with harness = false is NOT reported
+        .stderr(contains("bencher_correct").not());
+    teardown(dir);
+}

crates/cargo-codspeed/tests/helpers.rs

@@ -22,6 +22,7 @@ pub enum Project {
     Workspace,
     PackageInDeps,
     CratesWorkingDirectory,
+    DefaultHarnessError,
 }
 
 pub fn setup(dir: &str, project: Project) -> String {
@@ -38,7 +39,7 @@ pub fn setup(dir: &str, project: Project) -> String {
     let package_root = PathBuf::from_str(env!("CARGO_MANIFEST_DIR")).unwrap();
     let workspace_root = package_root.parent().unwrap().parent().unwrap();
     match project {
-        Project::Simple | Project::Features => {
+        Project::Simple | Project::Features | Project::DefaultHarnessError => {
             replace_in_file(
                 tmp_dir.join("Cargo.toml").to_str().unwrap(),
                 "../../..",