assertTrue(t instanceof Runnable, "TestLocking should implement Runnable");
    }

    @Test
    @DisplayName("run method handles null URL gracefully")
    void testRunWithNullUrl() {
        TestLocking t = new TestLocking();
        t.url = null; // Null URL
        t.numIter = 0; // No iterations to avoid NPE

        // Should not throw exception