}

    public void test_convertFyu_BugFix() {
        // Test that フュ correctly maps to "fyu" only (not "hyu")
        List<String> results = converter.convert("フュ", null);
        assertTrue(results.contains("fyu"));
        assertFalse("Should not contain 'hyu' (that's for ヒュ)", results.contains("hyu"));
    }

    public void test_convertEmptyString() {
        List<String> results = converter.convert("", null);