How to test NGXS in Angular applications

If you need to avoid mocking NGXS in your modules, use .keep.

beforeEach(() =>
   MockBuilder(TargetComponent, TargetModule)
     
     // NgxsModule.forRoot() is called in TargetModule or its imports 
     .keep(NgxsModule.forRoot().ngModule) // keeps all NgxsModule.forRoot
     
     // add it only if your module imports NgxsModule.forFeature
     // NgxsModule.forFeature() is called in TargetModule or its imports
     .keep(NgxsModule.forFeature().ngModule) // keeps all NgxsModule.forFeature
     
     // keeps the root provider of the store
     .keep(Store)
 );

If your module imports only NgxsModule.forFeature, you need to add NgxsModule.forRoot() and Store manually:

beforeEach(() =>
   MockBuilder(
     // keep and export
     [
       TargetComponent,
       NgxsModule.forRoot(), // provides required services
       Store, // keeps the root provider of the store
     ],
     // mock
     TargetModule,
   ).keep(NgxsModule.forFeature().ngModule) // keeps all NgxsModule.forFeature
 );