Decouple from ExUnit

[marnen]

WhiteBread.Context brings in ExUnit.Assertions, which was conflicting with the ESpec functions that I want to use in my steps. So I made the test library configurable, defaulting to ExUnit.

Really, though, I only did it this way to avoid breaking existing behavior. In the longer term, I don't actually think that WhiteBread.Context should import a testing library at all out of the box. I'd rather see something like this:

defmodule MyProject.Context
  defmacro __using__(_opts) do
    quote do
      use WhiteBread.Context # without testing library being loaded
      import ExUnit.Assertions
    end
  end
end

defmodule MyProject.StepDefinitions
  use MyProject.Context
end

What do you think?

[marnen]

Yes, this is a function that returns a quoted block. It seemed like the right thing here, but I'm open to other ideas (considering I'm a relative beginner in Elixir...).

[meadsteve]

Seems a sensible approach to me here. It's relatively easy to follow what it's doing.

[marnen]

I realized that I don't know the answer to this question: if macros are evaluated at compile time, will the fact that this is a function cause any problems? (It's been working well for me, but I just want to make sure that I didn't stumble into an Elixir gotcha.)

[meadsteve]

@marnen I really like this approach. I actually now regret defaulting to always importing ExUnit.Assertions. I think I took the "batteries included" approach a little too far.

[meadsteve]

One small change request. Can this be pulled out as @default_test_library so that we have

opts = Keyword.merge [test_library: @default_test_library], opts

and further up the file:

@step_keywords [:given_, :when_, :then_, :and_, :but_]
@default_test_library :ex_unit

[marnen]

That sounds like a good idea.

[marnen]

I also made the error message a little clearer here by printing the bad value.

[marnen]

I think this is probably ready to merge now.