public void test_assertPropertyNotNull_withNonNull() {
        TestFessLabels labels = new TestFessLabels();
        // Should not throw exception
        labels.testAssertPropertyNotNull("test");
        labels.testAssertPropertyNotNull("");
        labels.testAssertPropertyNotNull(" ");
    }

    // Helper class to test protected method
    private static class TestFessLabels extends FessLabels {