While writing mocks for an Elixir test suite, I found that mock_with sets up a global mock object which prevents you from safely being able to set a test as async: true.

We’ve been using Mox reliably to mock out our own internal code by setting the @callback attribute on methods we wish to mock, thus treating them as behaviours.

The trouble we’ve hit is when we need to mock a third party module, e.g. Redix (a Redis client). We can patch their library with the relevant @callback attributes, but is there a better and cleaner way to implement unobtrusive, async-friendly mocks for third party code?

It’d be awesome to get a community consensus on this!