CoroutineTestExtension does not always use Dispatchers.setMain()

[RBusarow]

Any time the extension injects a new scope via constructor or function argument, it puts that scope into a MutableMap where the key its the ExtensionContext. This map is used in beforeEach to call setMain(...) and in afterEach to call resetMain() and cleanUpTestCoroutines().

This is the existing beforeEach:

  override fun beforeEach(context: ExtensionContext) {
    contextScopeMap[context]?.dispatcherProvider?.main?.let {
      Dispatchers.setMain(it)
    }
  }

Here's a simplified timeline of a JUnit5 test execution with parameter resolution:

1. Initialize extension (no context here for the internal scope property).
2. Create constructor dependencies and add to map.
3. Create class.
4. beforeEach()
5. Create function dependencies and add to map.
6. Execute test function with parameters.
7. afterEach()

Dispatchers.setMain(...) works with constructor parameters because they've been added to the map before beforeEach() is invoked. It doesn't work with the internal scope property because it's never added to the map. It also doesn't work for injected function parameters because they're constructed and added to the map after beforeEach() is invoked.