Enable Unit Testing of Durable Functions

[Cho-William]

💡 Feature description

What would you like to see, and why?

I've been developing a few durable functions, and I've come to realize that there is no real way to mock a azure.durable_functions.DurableOrchestrationContext object. It would be ideal if we could have this available to unit test durable functions. The current documentation seems to expect the developer to just run a local integration test.

What kinds of usage do you expect to see in this feature?

Per above, mocking the orchestration context would allow unit-testing of durable functions.

💭 Describe alternatives you've considered

What are other ways to achieve this? Have you thought of alternative designs or solutions?

For now, I am resorting to just defining test classes that perform the core actions of my durable functions without requiring a context object. These test classes interface with Azurite to mock up necessary containers.

Any existing workarounds? Why are they not sufficient? We'd like to know!

This was rather naive, but I tried debugging a manual integration test and copying the context's json string, then feeding it to the client constructor in my unit testing. I will note that this would not even work in theory, since the context json values are tied to dynamically created resources.

Additional context

Add any other context or screenshots about the feature request here.

Question: what is the current guidance for testing durable functions, besides manually performing an integration test?
Question: is the following approach valid to emulate unit-testing: refactoring logic that does not require a context to separate classes so that they are accessible for unit-testing?