@Test
public void testDecode() {

    // przypadki testowe
    Object[][] testCases = {
        {"0", 0L},
        {"-99", -99L},
        {"2147483648", 2147483648L},
        {null, null},
        {"", null},
        {"\t \n", null}
    };
    // wykonanie testow
    for (Object[] testCase : testCases) {
        String text = (String) testCase[0];
        Long expectedValue = (Long) testCase[1];
        IntegerHolder holder = type.decode(text);
        assertEquals(expectedValue, holder.getValue());
    }
}