HelperMethods { static Boolean isBlank(String str) { return str == null || str.isEmpty(); }    }
@Test public void isBlank_shouldReturnTrueIfStringIsNull() { assertThat(HelperMethods.isBlank(null)).isTrue(); }
@Test public void isBlank_shouldReturnTrueIfStringIsEmpty() { assertThat(HelperMethods.isBlank("")).isTrue(); }
@Test public void isBlank_shouldReturnFalseIfStringHasContent() { assertThat(HelperMethods.isBlank("a")).isFalse(); }