fix(core): reset tView between tests in Ivy TestBed (#38659)

`tView` that is stored on a component def contains information about directives and pipes
that are available in the scope of this component. Patching component scope causes `tView` to be
updated. Prior to this commit, the `tView` information was not restored/reset in case component
class is not declared in the `declarations` field while calling `TestBed.configureTestingModule`,
thus causing `tView` to be reused between tests (thus preserving scopes information between tests).
This commit updates TestBed logic to preserve `tView` value before applying scope changes and
reset it back to the previous state between tests.

Closes #38600.

PR Close #38659

packages/core/test/test_bed_spec.ts

@@ -1126,6 +1126,63 @@ describe('TestBed', () => {
              expect(SomePipe.hasOwnProperty('ɵpipe')).toBeTruthy();
            });
 
+        it('should cleanup scopes (configured via `TestBed.configureTestingModule`) between tests',
+           () => {
+             @Component({
+               selector: 'child',
+               template: 'Child comp',
+             })
+             class ChildCmp {
+             }
+
+             @Component({
+               selector: 'root',
+               template: '<child></child>',
+             })
+             class RootCmp {
+             }
+
+             // Case #1: `RootCmp` and `ChildCmp` are both included in the `declarations` field of
+             // the testing module, so `ChildCmp` is in the scope of `RootCmp`.
+             TestBed.configureTestingModule({
+               declarations: [RootCmp, ChildCmp],
+             });
+
+             let fixture = TestBed.createComponent(RootCmp);
+             fixture.detectChanges();
+
+             let childCmpInstance = fixture.debugElement.query(By.directive(ChildCmp));
+             expect(childCmpInstance.componentInstance).toBeAnInstanceOf(ChildCmp);
+             expect(fixture.nativeElement.textContent).toBe('Child comp');
+
+             TestBed.resetTestingModule();
+
+             // Case #2: the `TestBed.configureTestingModule` was not invoked, thus the `ChildCmp`
+             // should not be available in the `RootCmp` scope and no child content should be
+             // rendered.
+             fixture = TestBed.createComponent(RootCmp);
+             fixture.detectChanges();
+
+             childCmpInstance = fixture.debugElement.query(By.directive(ChildCmp));
+             expect(childCmpInstance).toBeNull();
+             expect(fixture.nativeElement.textContent).toBe('');
+
+             TestBed.resetTestingModule();
+
+             // Case #3: `ChildCmp` is included in the `declarations` field, but `RootCmp` is not,
+             // so `ChildCmp` is NOT in the scope of `RootCmp` component.
+             TestBed.configureTestingModule({
+               declarations: [ChildCmp],
+             });
+
+             fixture = TestBed.createComponent(RootCmp);
+             fixture.detectChanges();
+
+             childCmpInstance = fixture.debugElement.query(By.directive(ChildCmp));
+             expect(childCmpInstance).toBeNull();
+             expect(fixture.nativeElement.textContent).toBe('');
+           });
+
         it('should clean up overridden providers for modules that are imported more than once',
            () => {
              @Injectable()

packages/core/testing/src/r3_test_bed_compiler.ts

@@ -379,6 +379,11 @@ export class R3TestBedCompiler {
       const moduleScope = getScopeOfModule(moduleType);
       this.storeFieldOfDefOnType(componentType, NG_COMP_DEF, 'directiveDefs');
       this.storeFieldOfDefOnType(componentType, NG_COMP_DEF, 'pipeDefs');
+      // `tView` that is stored on component def contains information about directives and pipes
+      // that are in the scope of this component. Patching component scope will cause `tView` to be
+      // changed. Store original `tView` before patching scope, so the `tView` (including scope
+      // information) is restored back to its previous/original state before running next test.
+      this.storeFieldOfDefOnType(componentType, NG_COMP_DEF, 'tView');
       patchComponentDefWithScope((componentType as any).ɵcmp, moduleScope);
     });