We currently have two long-standing issues related to how `TestBed` tests are torn down:
1. The dynamically-created test module isn't going to be destroyed, preventing the `ngOnDestroy` hooks on providers from running and keeping the component `style` nodes in the DOM.
2. The test root elements aren't going to be removed from the DOM. Instead, they will be removed whenever another test component is created.
By themselves, these issues are easy to resolve, but given how long they've been around, there are a lot of unit tests out there that depend on the broken behavior.
These changes address the issues by introducing APIs that allow users to opt into the correct test teardown behavior either at the application level via `TestBed.initTestEnvironment` or the test suite level via `TestBed.configureTestingModule`.
At the moment, the new teardown behavior is opt-in, but the idea is that we'll eventually make it opt-out before removing the configuration altogether.
Fixes#18831.
PR Close#42566
Currently we have a lot of places where we repeat the type `Type<T>|AbstractType<T>|InjectionToken<T>` which makes it cumbersome to add another type or to type something else with the same signature.
These changes add a new type that can be used instead.
Fixes#39792.
PR Close#41580
```
export const __core_private_testing_placeholder__ = '';
```
This API should be removed. But doing so seems to break `google3` and
so it requires a bit of investigation. A work around is to mark it as
`@codeGenApi` for now and investigate later.
PR Close#38274
Moves the public api .d.ts files from tools/public_api_guard to
goldens/public-api.
Additionally, provides a README in the goldens directory and a script
assist in testing the current state of the repo against the goldens as
well as a command for accepting all changes to the goldens in a single
command.
PR Close#35768
Paul Gschwendtner
Kristiyan Kostadinov
JiaLiPassion
Misko Hevery
Joey Perrott