assertTrue(emptyGenerator.isAvailable());
        // Test cached availability
        assertTrue(emptyGenerator.isAvailable());
    }

    @Test
    public void test_isTarget() {
        // Initialize without container
        emptyGenerator = new EmptyGenerator();

        // Note: isTarget method requires FessConfig from ComponentUtil
        // which needs container initialization.

    public void test_isAvailable() {
        // Test default implementation
        generator = new TestThumbnailGenerator();
        assertTrue(generator.isAvailable());
    }

    @Test
    public void test_isTarget() {
        // Test isTarget method
        generator = new TestThumbnailGenerator();
        Map<String, Object> docMap = new HashMap<>();

        // Note: isTarget requires FessConfig which needs container