Allow MockedProvider to accept a schema plus resolver mocks.

[macrozone]

Migrated from: apollographql/react-apollo#3108

[davidroeca]

This feature would resolve a number of issues. I think the root of this feature request would be to support resolvers as functions that can accept variable arguments, rather than requiring the variables to be hard-coded in the mocks themselves. Maybe there's a better approach than just taking the interface from graphql-tools, but providing a similar feature would be incredibly beneficial.

Here are a few adjacent issues which could be resolved with something like this:

• [Feature Request] Create dynamicVariables for mutation MockedProvider #89 - a function can generate dynamic variables
• Ability to use wildcards in mocks / mock a range of requests #206 - a function could accept any variables/ignore them
• MockedProvider should not match when given extra variables #173 (this one is a behavioral issue that could be resolved with a functional interface)
• feat req: Improve "No more mocked responses for the query" message #115 - datetimes cause some issues and require string-literal work-arounds

My current work-around is to define mock data, and then iterate over every possible value to create a large array of mocks that handles all possible values. Note that some of the above issues are not completely resolved with this work-around and require their own work-arounds as well.

I understand why there may be some hesitance here because there may be compatibility issues between some of these libraries. However, the alternative in userland is a sad mess of complex test data + mock generation which I'd argue is more confusing test setup than a function.

I wonder if there's a simple way to accommodate a functional interface like the one mentioned in this issue.

[dylanwulf]

I've been using an approach similar to this which works really well for me. I think it solves all the problems brought up in this issue so far: https://medium.com/free-code-camp/a-new-approach-to-mocking-graphql-data-1ef49de3d491

[davidroeca]

I've used that approach as well and I agree that it's a better interface than the MockedProvider, and was actually the only way to mock the schema a few years back. However, I've found that interface to to be unstable between differing apollo dependencies, and upgrading apollo versions was challenging.

I assume these sorts of challenges are part of the reason we have a MockedProvider in the first place, in addition to its simplicity. This is why I'd like for the apollo team to consider improvements to the MockedProvider itself.

[alessbell]

Hi all 👋 You may be interested in the RFC I've just opened for a new schema-driven testing utility: apollographql/apollo-client#11705

It doesn't directly resolve this feature request, but I believe it has certain DX advantages over a provider-style API and would love to hear your thoughts over on that issue :)

[macrozone]

@alessbell thanks for sharing and nice that this issue got an update! (i completly forgot about that)