:actor Main
  :new (env)
    Spec.Process.run(env, [
      Spec.Run(AdditionSpec).new(env)
    ])

:class AdditionSpec
  :is Spec
  :const describes: "Addition"

  :: Return the number 2 (written in hex, just for fun).
  :const _two U64'val: 0x02

  :it "adds two twos"
    assert: @_two + '\x02' == 4

  :: Raise an error if the argument is positive.
  :fun non add_overflow!(a U64'val, b U64'val): a +! b

  :it "can error on overflow"
    integers Array(U64)'val = [99, 100, 101]

    // Check addition overflow for various pairs of addends.
    assert error: add_overflow!(U64.max_value, 1)
    assert no_error: add_overflow!(U64.max_value, 0)
    assert no_error: add_overflow!(integers[0]!, 1)

    // Print a bit of extra information using string interpolation.
    @env.out.print("The first integer is \(integers[0]!)")