@Test
public void testBlockComment_withEmptyQuotedPattern() {

  Parser<Void> scanner = Scanners.blockComment("<<", ">>", Patterns.ALWAYS);
  assertNull(scanner.parse("<<>>"));
  assertFailure(mode, scanner, "<<a>>", 1, 3);
  assertFailure(mode, scanner, "", 1, 1);
  assertFailure(mode, scanner, "a", 1, 1);
}