Log unmatched mocks to the console for tests

[jerelmiller]

Closes #5917

When using MockedProvider to mock responses for a component under test, there is a chance a mock is not matched when the request was made, typically due to user-error like a typo or mismatched variable. Currently this results in an error response returned from the MockLink. In some situations, limiting the mismatch to an error response made it difficult to debug issues with the test setup, such as when the errorPolicy was set to ignore, which discards errors returned from links.

This PR will now log console warnings when a mock cannot be matched during a test. This should make it more obvious that there could be potential issues with the test setup.

Occasionally, an unmatched mock is expected for a test. In this case, you can disable these warnings with the newly introduced showWarnings option. This can be set either through the MockedProvider or MockLink.

// Using `MockedProvider`
<MockedProvider showWarnings={false} />

// Using `MockLink`
new MockLink(mocks, false, { showWarnings: false });

Checklist:

• If this PR contains changes to the library itself (not necessary for e.g. docs updates), please include a changeset (see CONTRIBUTING.md)
• If this PR is a new feature, please reference an issue where a consensus about the design was reached (not necessary for small changes)
• Make sure all of the significant new logic is covered by tests

[changeset-bot]

🦋 Changeset detected

Latest commit: f184d7a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@apollo/client	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[alessbell]

LGTM overall, this will be a huge improvement on the testing side 🙌🙌 My one comment re: naming is because I personally struggle with double negatives and find them confusing, and I think this is a case where we can avoid it, but happy to discuss more 👍

[jerelmiller]

Some of the test failures are legitimate since they check console warnings and we have now introduced a new one, which breaks some existing tests. I'm currently evaluating how to proceed, given they use mockSingleLink, which isn't friendly to work with to the new options argument passed to MockLink.

[adamesque]

News of this PR has been making the rounds internally at my company and we're celebrating. :) Thanks very much!

[jerelmiller]

@adamesque that's great to hear! Glad to hear it will be helpful!