List<String> results = converter.convert("アイウ", null);
        for (String result : results) {
            assertEquals(result, result.toLowerCase());
        }
    }

    public void test_convertHalfWidth() {
        // Test that full-width characters are converted to half-width
        List<String> results = converter.convert("アイウ", null);
        for (String result : results) {