fix(store): provide the same instance of MockStore

[lacolaco]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https:/ngrx/platform/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Currently, TestBed.inject(Store) returns a different instance to TestBed.inject(MockStore). So the test below fails.

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [AppComponent],
      providers: [
        provideMockStore(),
      ]
    }).compileComponents();
  }));

  it("mockstore providers", () => {
    const storeA = TestBed.inject(Store);
    const storeB = TestBed.inject(MockStore);
    expect(storeA).toBe(storeB); // => FAIL
  });

Users expect they are the same because it is mocking.

What is the new behavior?

It solved.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

Angular CLI: 9.0.2
Node: 12.13.0
OS: darwin x64

Angular: 9.0.1
... animations, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router
Ivy Workspace: Yes

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.900.2
@angular-devkit/build-angular     0.900.2
@angular-devkit/build-optimizer   0.900.2
@angular-devkit/build-webpack     0.900.2
@angular-devkit/core              9.0.2
@angular-devkit/schematics        9.0.2
@angular/cli                      9.0.2
@ngtools/webpack                  9.0.2
@schematics/angular               9.0.2
@schematics/update                0.900.2
rxjs                              6.5.4
typescript                        3.7.5
webpack                           4.41.2

[ngrxbot]

Preview docs changes for 1a5935e at https://previews.ngrx.io/pr2381-1a5935e/

[alex-okrushko]

Thanks @lacolaco !

[alex-okrushko]

Actually, would you mind adding that test to https:/ngrx/platform/blob/master/modules/store/testing/spec/mock_store.spec.ts ?

[lacolaco]

@alex-okrushko Sure! wait a moment plz 😉

[timdeschryver]

Thanks @lacolaco !

[mjudde]

Would it be possible to have this fix on NGRX 8.6 ?

[alex-okrushko]

@brandonroberts WDYT?