Mock redis

[nichochar]

Main upgrade

Now that we've deprecated support for python 3.3 and python 2.6, we can use a compatible library to mock redis.

I looked into using redislite, but the client.setex function has a different signature which is incompatible, and required a bit of ugly gluing together.

I also tried mockredis and I'm much happier with the simple syntax.

One of the only downsides is that we have to expire keys automatically with a client.do_expire() in the tests, but I think this is acceptable.

Note that it's still possible to perform integration tests with a real redis, simply do not set the MOCK_REDIS ENV variable

Side upgrades

Upgraded tox, pytest and pytest cov to use the latest versions

[jparise]

Why does this need to be patched?

It would be nice not to do this because it's the only place the mock package is used.

[nichochar]

In general I much prefer mocking third party services like redis than perform an integration test.

The biggest pro for me is that this allows for local development without having to include Redis. We can still add an integration test with redis on travis if we're still interested.

As for introducing the mock package, it's not ideal but I personally don't think that cost is too high.

Happy to discuss this further.

[jparise]

I think I understand. The patching is used here because there's no another way for this test case to always use mock_strict_redis_client should some kind of dependency injection, etc. when MOCK_REDIS isn't defined. Is that right?

[nichochar]

Correct, because of how the client is initialized in the main logic, this is the only way I found to replace all instances of the redis_client with the mock one.