Comment by molf

But ultimately it suggests this test; which only tests an empty loop?

  def test_empty_drc():
      drc = Mock(
          spec_set=DockerRegistryClient,
          get_repos=lambda: []
      )

      assert {} == get_repos_w_tags_drc(drc)

Maybe it's just a poor example to make the point. I personally think it's the wrong point to make. I would argue: don't mock anything _at all_ – unless you absolutely have to. And if you have to mock, by all means mock code you don't own, as far _down_ the stack as possible. And only mock your own code if it significantly reduces the amount of test code you have to write and maintain.

I would not write the test from the article in the way presented. I would capture the actual HTTP responses and replay those in my tests. It is a completely different approach.