@Test
public void testEncode() {

    // przypadki testowe
    Object[][] testCases = {
        {new StringHolder("ABC"), "ABC"},
        {new StringHolder(""), ""},
        {new StringHolder(null), null}
    };
    // wykonanie testow
    for (Object[] testCase : testCases) {
        StringHolder holder = (StringHolder) testCase[0];
        String expectedResult = (String) testCase[1];
        String result = type.encode(holder);
        assertEquals(expectedResult, result);
    }
}