@Test
public void testIsEmpty() {

    final String nullString = null;
    final String emptyString = "";
    final String blankString = " ";
    final String string = "a";
    assertThat(Strings.isEmpty(nullString), is(true));
    assertThat(Strings.isEmpty(emptyString), is(true));
    assertThat(Strings.isEmpty(blankString), is(false));
    assertThat(Strings.isEmpty(string), is(false));
}