     parseTest(
       "abc", concat("a", "b", "c"))
     parseTest(
-      "abc\\+d*",
+      #"abc\+d*"#,
       concat("a", "b", "c", "+", .zeroOrMore(.greedy, "d")))
     parseTest(
       "a(b)", concat("a", .group(.capture(), "b")))


extension RegexTests {
  func testParse() {
    _ = """
        Examples:
            "abc" -> .concat(｢abc｣)
            "abc\\+d*" -> .concat(｢abc+｣ .zeroOrMore(｢d｣))
            "abc(?:de)+fghi*k|j" ->
                .alt(.concat(｢abc｣, .oneOrMore(.group(.concat(｢de｣))),
                             ｢fgh｣ .zeroOrMore(｢i｣), ｢k｣),
                     ｢j｣)
        """

    func alt(_ asts: AST...) -> AST { return .alternation(asts) }
    func concat(_ asts: AST...) -> AST { return .concatenation(asts) }

    lexTest(
      "abc", "a", "b", "c")
    lexTest(
      #"ab\c"#, "a", "b", esc("c"))
    lexTest(
      #"abc\+d*"#, "a", "b", "c", esc("+"), "d", .star)
    lexTest(
      "abc(de)+fghi*k|j",
      "a", "b", "c", .leftParen, "d", "e", .rightParen,
