### Question:
StringUtils { public static String padLeft(String value, int minLength) { return padStart(value, minLength, '0'); } private  StringUtils(); static String padStart(String string, int minLength, char padChar); static boolean isNullOrEmpty(String string); static String padLeft(String value, int minLength);  }### Answer:
@Test void padLeft() { assertThat(StringUtils.padLeft("value", 10)).isEqualTo("00000value"); }
@Test void padLeft_throws_for_null_value() { assertThrows(NullPointerException.class, () -> StringUtils.padLeft(null, 10)); }
@Test void padLeft_length_does_not_exceed_length() { assertThat(StringUtils.padLeft("value", 3)).isEqualTo("value"); assertThat(StringUtils.padLeft("value", -10)).isEqualTo("value"); assertThat(StringUtils.padLeft("value", 0)).isEqualTo("value"); }