Failure when mocking exceptions about mock HOT 6 CLOSED

I'm running into the same issue. I think, it's a common case for a supporting library to throw exceptions and for us to handle the exceptions accordingly. And I sure would love the ability to test for that path too.

Referring to the documentation of Meck, there seems to be a provision for "expecting" exceptions.

Exceptions can be anticipated by Meck (resulting in validation still passing). This is intended to be used to test code that can and should handle certain exceptions indeed does take care of them:

5> meck:expect(dog, meow, fun() -> meck:exception(error, not_a_cat) end).
ok
6> catch dog:meow().
{'EXIT',{not_a_cat,[{meck,exception,2},
                    {meck,exec,4},
                    {dog,meow,[]},
                    {erl_eval,do_apply,5},
                    {erl_eval,expr,5},
                    {shell,exprs,6},
                    {shell,eval_exprs,6},
                    {shell,eval_loop,3}]}}
7> meck:validate(dog).
true

Is this something that we can support in Mock? I'm new to Elixir (and totally unfamiliar with Erlang), and haven't read up on macros. Otherwise, would love to contribute back.

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Btw, I stopped using mock in favor of dependency injection.

from mock.

That's good to know @emilsoman. Is there a different library you are using to achieve it? Or can you point me at a place where I can understand how to do this in elixir?

Thanks,
Kalyan

from mock.

Here's a quick demo of how I changed my code for DI :

#Change this ->
defmodule MyModule do
  def get_project(url, dir) do
    Git.clone(url, dir)
  end
end


# to this ->
# See how we use a default argument.
# This means the consumers of this function don't
# have to know this change and everything works!
defmodule MyModule do
  def get_project(url, dir, scm \\ Git) do
    scm.clone(url, dir)
  end
end

Now you can test it like this:

test "get_project clones a repo using scm" do
  defmodule FakeGit do
    def clone(url, dir) do
      send self, {url, dir}
    end
  end

  MyModule.get_project("fake_url", "fake_dir", FakeGit)

  receive do
    {url, dir} ->
      assert url == "fake_url"
      assert dir == "fake_dir"
  end
end

There are other ways to do this. Check this blog post. But I find DI using function arguments the best way to do this, YMMV.

from mock.

Thanks Emil for those pointers. Very helpful!

from mock.

Going to close out this issue.

Simply for the record, I did want to point out that erlang code can be executed from within elixir. For example: meck:expect(..) can be written as `:meck.expect(...).

from mock.