@Test
public void testStringCaseInsensitive() {

  Parser<Void> scanner = Scanners.stringCaseInsensitive("ab");
  assertNull(scanner.parse("ab"));
  assertNull(scanner.parse("AB"));
  assertNull(scanner.parse("aB"));
  assertFailure(mode, scanner, "", 1, 1, "ab expected, EOF encountered.");
  assertFailure(mode, scanner, "a", 1, 1);
}