### Question:
StellaStringUtils { public static String leftPadWithZeros(String input, int expectedSize){ if( input == null ) { return leftPadWithZeros("", expectedSize); } StringBuilder sb = new StringBuilder(expectedSize); for (int i = expectedSize - input.length(); i>0; i-- ){ sb.append(ZERO); } sb.append(input); return sb.toString(); }  static String leftPadWithZeros(String input, int expectedSize); static String prefixNotNullStringOrDefault(String str, String defaultStr, String prefix); static String suffixNotNullStringOrDefault(String str, String defaultStr, String suffix);  }### Answer:
@Test public void deveCompletarUmaStringComZerosAEsquerda() { String value = "123"; String result = StellaStringUtils.leftPadWithZeros(value, 5); assertEquals("00123", result); }
@Test public void naoDeveApendarNadaSeOtamanhoJaEhCerto() { String value = "12345"; String result = StellaStringUtils.leftPadWithZeros(value, 5); assertEquals("12345", result); }
@Test public void naoDeveApendarNadaSeOtamanhoEhMenorQueAString() { String value = "12345"; String result = StellaStringUtils.leftPadWithZeros(value, 4); assertEquals("12345", result); }
@Test public void deveCompletarUmaStringComZerosAEsquerdaQuandoValorForNulo() { String value = null; String result = StellaStringUtils.leftPadWithZeros(value, 5); assertEquals("00000", result); }