test: ensure unique /tmp/ps test dirs

Author: YusukeShimizu

test/setup.go

@@ -47,7 +47,11 @@ func makeTestDataDir(t *testing.T) string {
 	shortBase := "/tmp/ps"
 	if err := os.MkdirAll(shortBase, 0o755); err == nil {
 		// Use process ID and timestamp for uniqueness
-		testDir := filepath.Join(shortBase, fmt.Sprintf("%d-%d", os.Getpid(), time.Now().UnixNano()%1000000))
+		// NOTE: Avoid using a modulus on the timestamp here. These integration
+		// tests run in parallel in CI, and collisions would cause different test
+		// harnesses to share the same datadir (leading to flaky failures such as
+		// "lightningd already running? Error locking PID file").
+		testDir := filepath.Join(shortBase, fmt.Sprintf("%d-%d", os.Getpid(), time.Now().UnixNano()))
 		if err := os.MkdirAll(testDir, 0o755); err == nil {
 			t.Cleanup(func() {
 				if err := os.RemoveAll(testDir); err != nil {