} catch (IllegalArgumentException e) {
            assertEquals("name or scriptEngine is null.", e.getMessage());
        }
    }

    // Test add multiple engines
    public void test_add_multipleEngines() {
        TestScriptEngine engine1 = new TestScriptEngine("engine1");
        TestScriptEngine engine2 = new TestScriptEngine("engine2");
        CustomScriptEngine customEngine = new CustomScriptEngine();