[BUG]: 'Expect' expressions in some tests of async operations are not running

[mgporter]

Describe the bug

While working on a PR, I discovered that some asynchronous frontend tests would succeed, even when they should have failed. This particular behavior was found in core/templates/pages/contributor-dashboard-page/services/contribution-and-review.service.spec.ts, however it may be present in other tests as well.

URL of the page where the issue is observed.

core/templates/pages/contributor-dashboard-page/services/contribution-and-review.service.spec.ts

Steps To Reproduce

Below is a video to show the problem. In this video:

1. I start with a test already in the code that succeeds (forgot to record it succeeding, sorry)
2. I change a spy to return a Promise that resolves to null, instead of its original data
3. I run the test and show it still succeeding (test compilation process is sped up FYI). The test should have failed in this step.
4. Then I try out one fix to the problem: I change the function to async and add an await so that the expect method has a chance to run inside the then method
5. I run the test again and show how it now fails (as it should)

This issue seems to appear whenever a test covers an asynchronous method and puts expect expression inside the callback to the chained then method, without returning a Promise or using await. The Jasmine documentation for async functions does not show tests done in this way, and it appears to not work.

Expected Behavior

As noted above, changing the spy to return a Promise that resolves to null should have caused the test to fail in step 3.

Screenshots/Videos

Oppia-Async-Test-Bug.mp4

What device are you using?

Desktop

Operating System

Linux

What browsers are you seeing the problem on?

No response

Browser version

No response

Additional context

Once we establish how to modify the tests so that they run correctly, I would be willing to work on the changes.

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