Capture_io can has mock input and ExUnit.Server stops when getting :eof as an input

[mururu]

discussing at #919

Using this patch, we can test IEx like the following.

ExUnit.start []

defmodule IEx.InteractiveTest do
  use ExUnit.Case, async: true

  import ExUnit.CaptureIO

  setup_all do
    :application.start(:iex)
  end

  setup do
    scope = :elixir.scope_for_eval(
      file: "iex",
      delegate_locals_to: IEx.Helpers
    )

    config=IEx.Config[
      binding: [],
      scope: scope,
    ]

    { :ok, config: config }
  end


  test "iex", context do
    input  = %B"""
             a = 2
             a + 3
             """
    expect = %B"""
             2
             5
             """

    assert capture_io(input, fn ->
      IEx.Server.start(context[:config])
    end) |> strip == expect
  end

  test "#iex:break", context do
    input = %B"""
            "a
            #iex:break
            """

    output = capture_io(input, fn ->
      IEx.Server.start(context[:config])
    end) |> strip

    assert output =~ %r/TokenMissingError/
    assert output =~ %r/incomplete expression/
  end


  defp strip(output) do
    output |> String.split("\n") |> tl |> Enum.join("\n")
  end
end

[josevalim]

This is awesome! ❤️ 💚 💙 💛 💜

[josevalim]

Can we make the default input to be an empty string? If we have an empty string, it means we also reached the end of the file...

[josevalim]

If we do it, we can force the input to always be a binary!

[alco]

@josevalim Empty string doesn't mean the end of input in general. If you're going to use capture_io for anything other than iex, it'll might not behave well.

[josevalim]

It seems the code treat them as the same though, no?

[mururu]

I think the difficult point is IO includes various IO. When a developer deal with standard IO(a keyboard and a display), he don't have to necessarily consider :eof, but when he deal with file IO, he have to consider :eof.

[josevalim]

Perfect. :) Ok! let me know when we can merge this! :D

[mururu]

I fixed typo. Please merge this.

[josevalim]

Merged (with pleasure)!

[mururu]

Thanks! :D