@Test
public void testEncode() {

    // przypadki testowe
    Object[][] testCases = {
        {-100L, "-100"},
        {0L, "0"},
        {999L, "999"},
        {2147483648L, "2147483648"},
        {null, null}
    };
    // wykonanie testow
    for (Object[] testCase : testCases) {
        Long number = (Long) testCase[0];
        String expectedResult = (String) testCase[1];
        String result = type.encode(new IntegerHolder(number));
        assertEquals(expectedResult, result);
    }
}