Testing dependency providers

[Davis Kirkendall]

Is there a preferred way for testing dependency providers and entrypoints? 

Granted, the basic idea of nameko is to have dependency providers be the layer into the outside world that is mocked out during testing, but in many cases the providers themselves need quite complex logic (spawned managed threads, deserialization of inbound data and so on).

So I'd be interested in the solutions out there especially since the story for testing service logic (worker factory, dependency replacement and so on) in nameko is really nice!

[Matt Yule-Bennett]

This is a great question. There aren't as many simple approaches for this as there are for testing service logic.

I generally do a couple of things:

1. Separate what is injected by the DependencyProvider from the part that manages the lifecycle, and unit test them both independently. A very limited example of this is the toy Travis webservice DP in the Nameko docs. The service interface (ApiWrapper) can be easily instantiated using mock or fake objects and the unit tested against them. 

2. Some limited functional testing of the DependencyProvider or Entrypoint in situ, to make sure that it is working correctly. Most of the community extensions (e.g. nameko-amqp-retry) are tested in this way.

For the functional testing there are several helpers that you may find useful:

get_extension - Extract the bound instance of an extension from a container

entrypoint_hook - Execute a service method on a running container without invoking the entrypoint. Gives you back the return value of exception from the method.

entrypoint_waiter - Block until an entrypoint-decorated method is executed. Accepts a callback so you can wait for specific args or return values.

wait_for_call - Like entrypoint_waiter but for any method on any object.

Hope that helps.

Matt.