    @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"));
    }