deleteDirectory(tempDir.toFile());
        }
    }

    @Test
    public void test_createDirectories_existingPath() throws Exception {
        // Test that Files.createDirectories is idempotent (no exception on existing dir)
        Path tempDir = Files.createTempDirectory("toctou_test");
        try {
            Path existingPath = tempDir.resolve("existing");
            Files.createDirectories(existingPath);

        }
    }

    @Test
    public void test_completeOperation_doubleCall_safe() {
        // Calling completeOperation twice must not throw (idempotent release)
        final AtomicInteger callCount = new AtomicInteger(0);
        final CoordinatorHelper helper = new CoordinatorHelper() {
            @Override