@Test
public void testSpecialCharsAreNotValid() throws Exception {

    assertFalse(mAlphaNumeric.isValid("ä"));
    assertFalse(mAlphaNumeric.isValid("ö"));
    assertFalse(mAlphaNumeric.isValid("ü"));
    assertFalse(mAlphaNumeric.isValid("ß"));
}