There is an inconsistency in overrideProvider behaviour. Testing documentation says
(https://angular.io/guide/testing-components-basics#createcomponent) that all override...
methods throw error if TestBed is already instantiated. However overrideProvider doesn't throw any error, but (same as
other override... methods) doesn't replace providers if TestBed is instantiated. Add TestBed instantiation check to
overrideProvider method to make it consistent.
BREAKING CHANGE:
If you call `TestBed.overrideProvider` after TestBed initialization, provider overrides are not applied. This
behavior is consistent with other override methods (such as `TestBed.overrideDirective`, etc) but they
throw an error to indicate that, when the check was missing in the `TestBed.overrideProvider` function.
Now calling `TestBed.overrideProvider` after TestBed initialization also triggers an
error, thus there is a chance that some tests (where `TestBed.overrideProvider` is
called after TestBed initialization) will start to fail and require updates to move `TestBed.overrideProvider` calls
before TestBed initialization is completed.
Issue mentioned here: https://github.com/angular/angular/issues/13460#issuecomment-636005966
Documentation: https://angular.io/guide/testing-components-basics#createcomponent
PR Close#38717
c8f056beb6