extension ParsableArgumentsValidationTests {
    func test_shouldMaybeProduceUnknownOptionErrorInsteadOfMissingValue() throws {
      struct SomeArgs: ParsableArguments {
        @Option(name: .shortAndLong)
        var x_arg: Int

        @Option(name: .shortAndLong)
        var z_arg: Int
      }

      // swap order of 'x' and 'z' in the string to get different error output
      AssertErrorMessage(
        SomeArgs.self,
        [
          "-should_maybe_be_an_unknown_option_error_but_is_a_missing_value_error_when_it_includes_x_or_z",
        ],
        "Unknown option '-should_maybe_be_an_unknown_option_error_but_is_a_missing_value_error_when_it_includes_x_or_z'"
      )
      // actually: "Missing value for '-x <x_arg>'"
    }
}