@Test
public void testLineComment() {

  Parser<Void> scanner = Scanners.lineComment("#");
  assertNull(scanner.parse("#hello world"));
  assertScanner(mode, scanner, "#hello world\n", "\n");
  assertScanner(mode, scanner, "#hello world\r\n", "\n");
  assertScanner(mode, scanner, "#\n", "\n");
  assertNull(scanner.parse("#"));
  assertFailure(mode, scanner, "", 1, 1);
  assertFailure(mode, scanner, "\n", 1, 1);
  assertFailure(mode, scanner, "a", 1, 1);
}