Test framework for IEx

[alco]

Since most helpers are IO based, we can test it with a bash script.

Or set up a mock IO module that would send output to another process where we can check it against reference?

Update
I've renamed this to "Test framework for IEx". We can now write tests for some of the parts of IEx that haven't been automatically checked for regressions previously.

The purpose of this issue is:

• define the areas of IEx functionality that need to be automatically checked
• provide convenience macros/functions to reduce the amount boilerplate when writing such tests

Areas of interest I can point out are:

• check for proper exception catching
• test #iex:break
• test some or all of the helpers

[yrashk]

I'd rather replace the group leader to do this

[josevalim]

We can replace the group leader or have something like meck (for mocking IO calls). I think a mechanism for replacing the group leader will be needed in exunit sooner than later though.

[josevalim]

One option is to read the IO module used from :application.get_env(:iex, :io). Then the test can set it to something else, for example, a simple implementation that pushes stuff to the current process queue, like in the Mix.shell.

[alco]

This is partially implemented by #1059. Once we have the ability to mock use input, we can either close this one, or provide a helper itest macro dedicated to interactive testing:

def IExTests do
  use ExUnit.Case

  itest "input errors",
    input: "...",
    expected_output: "...",
    options: [:no_color]
end

[alco]

@mururu How is the work on updated capture_io going?

[mururu]

@alco I am woking on it now, but it is more difficult than I thought. Please wait for a few days.

[alco]

See updated issue description.

Areas of interest I can point out are:

• check for proper exception catching
• test #iex:break
• test some or all of the helpers

[alco]

Also

• test that .iex files are working properly

[josevalim]

Closed in favor of #1137.