test(cph-model): isolate version fixtures

Cargo.lock

@@ -427,6 +427,7 @@ version = "0.0.2"
 dependencies = [
  "cph-diag",
  "serde",
+ "tempfile",
  "toml",
 ]
 

crates/cph-model/Cargo.toml

@@ -10,3 +10,6 @@ serde = { workspace = true }
 # `preserve_order` keeps `[targets.*]` tables in TOML document order, which is
 # the declared order this crate exposes via `Lesson.targets` (ADR-0009).
 toml = { workspace = true, features = ["preserve_order"] }
+
+[dev-dependencies]
+tempfile = "3"

crates/cph-model/tests/load.rs

@@ -279,16 +279,15 @@ fn malformed_target_config_is_non_fatal_with_schema_violations() {
 /// match exactly (ADR-0016's MVP rule).
 const CPH_VERSION: &str = env!("CARGO_PKG_VERSION");
 
-/// Write a one-part lesson into a temp dir, optionally with a `.cph-version`
-/// file. Returns the temp dir so the caller runs `load`.
-fn tmp_lesson_with_version(version: Option<&str>) -> PathBuf {
-    let mut p = std::env::temp_dir();
-    let nanos = std::time::SystemTime::now()
-        .duration_since(std::time::UNIX_EPOCH)
-        .unwrap()
-        .as_nanos();
-    p.push(format!("cph-version-test-{nanos}"));
-    std::fs::create_dir_all(&p).unwrap();
+/// Write a one-part lesson into a uniquely-created temp dir, optionally with a
+/// `.cph-version` file. `TempDir` owns cleanup so parallel tests cannot delete
+/// one another's fixture after a timestamp collision.
+fn tmp_lesson_with_version(version: Option<&str>) -> tempfile::TempDir {
+    let tmp = tempfile::Builder::new()
+        .prefix("cph-version-test-")
+        .tempdir()
+        .unwrap();
+    let p = tmp.path();
     std::fs::write(
         p.join("manifest.toml"),
         "[project]\nid = \"v\"\nname = \"v\"\n[info]\ntitle = \"v\"\n[[parts]]\nkind = \"segment\"\npath = \"segments/a\"\n",
@@ -301,14 +300,13 @@ fn tmp_lesson_with_version(version: Option<&str>) -> PathBuf {
     if let Some(v) = version {
         std::fs::write(p.join(".cph-version"), v).unwrap();
     }
-    p
+    tmp
 }
 
 #[test]
 fn cph_version_matching_is_not_a_diagnostic() {
     let tmp = tmp_lesson_with_version(Some(CPH_VERSION));
-    let (_lesson, diags) = load(&tmp);
-    let _ = std::fs::remove_dir_all(&tmp);
+    let (_lesson, diags) = load(tmp.path());
     assert!(
         diags.iter().all(|d| d.code != DiagCode::CphVersionMismatch),
         "a matching .cph-version must not warn, got {diags:?}"
@@ -318,8 +316,7 @@ fn cph_version_matching_is_not_a_diagnostic() {
 #[test]
 fn cph_version_mismatch_is_an_error_diagnostic() {
     let tmp = tmp_lesson_with_version(Some("99.99.99"));
-    let (lesson, diags) = load(&tmp);
-    let _ = std::fs::remove_dir_all(&tmp);
+    let (lesson, diags) = load(tmp.path());
     // The lesson still loads (so other defects could surface), but the
     // mismatch is an error diagnostic — which alone makes it illegal.
     assert!(lesson.is_some(), "a mismatch should not halt loading");
@@ -339,8 +336,7 @@ fn cph_version_mismatch_is_an_error_diagnostic() {
 fn cph_version_missing_is_skipped() {
     // No `.cph-version` file at all → skipped (ADR-0016 migration period; OPEN).
     let tmp = tmp_lesson_with_version(None);
-    let (_lesson, diags) = load(&tmp);
-    let _ = std::fs::remove_dir_all(&tmp);
+    let (_lesson, diags) = load(tmp.path());
     assert!(
         diags.iter().all(|d| d.code != DiagCode::CphVersionMismatch),
         "a missing .cph-version must be skipped, got {diags:?}"
@@ -350,8 +346,7 @@ fn cph_version_missing_is_skipped() {
 #[test]
 fn cph_version_empty_is_an_error() {
     let tmp = tmp_lesson_with_version(Some("   \n"));
-    let (_lesson, diags) = load(&tmp);
-    let _ = std::fs::remove_dir_all(&tmp);
+    let (_lesson, diags) = load(tmp.path());
     assert!(
         diags
             .iter()