@Test
public void testToLowerCase() {

    final String nullString = null;
    final String emptyString = "";
    final String blankString = " ";
    final String string = "A";
    assertThat(Strings.toLowerCase(nullString), is(nullValue()));
    assertThat(Strings.toLowerCase(emptyString), is(""));
    assertThat(Strings.toLowerCase(blankString), is(" "));
    assertThat(Strings.toLowerCase(string), is("a"));
}