test(v0.4): cover lockfile release, contention, and stale removal

internal/lockfile/writelock_test.go

@@ -21,3 +21,82 @@ func TestAcquireCreatesLockFile(t *testing.T) {
 		t.Errorf("lock file should exist after Acquire: %v", err)
 	}
 }
+
+func TestReleaseRemovesLockFile(t *testing.T) {
+	dir := t.TempDir()
+	lockPath := filepath.Join(dir, "write.lock")
+
+	release, err := Acquire(lockPath, 2*time.Second, 10*time.Second)
+	if err != nil {
+		t.Fatalf("Acquire: %v", err)
+	}
+	release()
+
+	if _, err := os.Stat(lockPath); !os.IsNotExist(err) {
+		t.Errorf("lock file should be removed after release, got err=%v", err)
+	}
+}
+
+func TestReAcquireAfterRelease(t *testing.T) {
+	dir := t.TempDir()
+	lockPath := filepath.Join(dir, "write.lock")
+
+	r1, err := Acquire(lockPath, 2*time.Second, 10*time.Second)
+	if err != nil {
+		t.Fatalf("first Acquire: %v", err)
+	}
+	r1()
+
+	r2, err := Acquire(lockPath, 2*time.Second, 10*time.Second)
+	if err != nil {
+		t.Fatalf("second Acquire: %v", err)
+	}
+	r2()
+}
+
+func TestContentionTimesOut(t *testing.T) {
+	dir := t.TempDir()
+	lockPath := filepath.Join(dir, "write.lock")
+
+	r1, err := Acquire(lockPath, 2*time.Second, 10*time.Second)
+	if err != nil {
+		t.Fatalf("first Acquire: %v", err)
+	}
+	defer r1()
+
+	start := time.Now()
+	_, err = Acquire(lockPath, 300*time.Millisecond, 10*time.Second)
+	elapsed := time.Since(start)
+
+	if err == nil {
+		t.Fatal("expected timeout error, got nil")
+	}
+	if err != ErrTimeout {
+		t.Errorf("expected ErrTimeout, got %v", err)
+	}
+	if elapsed < 300*time.Millisecond {
+		t.Errorf("returned too early: %v < 300ms", elapsed)
+	}
+	if elapsed > 1*time.Second {
+		t.Errorf("returned too late: %v > 1s", elapsed)
+	}
+}
+
+func TestStaleLockIsRemoved(t *testing.T) {
+	dir := t.TempDir()
+	lockPath := filepath.Join(dir, "write.lock")
+
+	if err := os.WriteFile(lockPath, nil, 0644); err != nil {
+		t.Fatalf("planting stale lock: %v", err)
+	}
+	old := time.Now().Add(-5 * time.Second)
+	if err := os.Chtimes(lockPath, old, old); err != nil {
+		t.Fatalf("chtimes: %v", err)
+	}
+
+	release, err := Acquire(lockPath, 1*time.Second, 1*time.Second)
+	if err != nil {
+		t.Fatalf("Acquire should remove stale lock: %v", err)
+	}
+	defer release()
+}