added tests for https://github.com/HumanBrainProject/interactive-viewer/issues/465

src/services/effect/effect.spec.ts

 import {} from 'jasmine'
-import { getGetRegionFromLabelIndexId } from './effect'
+import { getGetRegionFromLabelIndexId, UseEffects } from './effect'
+import { TestBed } from '@angular/core/testing'
+import { Observable } from 'rxjs'
+import { SELECT_PARCELLATION, NEWVIEWER, SELECT_REGIONS } from '../state/viewerState.store'
+import { provideMockActions } from '@ngrx/effects/testing'
+import { hot } from 'jasmine-marbles'
+import { provideMockStore } from '@ngrx/store/testing'
+import { defaultRootState } from '../stateStore.service'
+
 const colinsJson = require('!json-loader!../../res/ext/colin.json')
 
+
 const hoc1 = {
   name: "Area hOc1 (V1, 17, CalcS) - left hemisphere",
   rgb: [
@@ -34,4 +43,43 @@ describe('effect.ts', () => {
       expect(fetchedRegion).toEqual(hoc1)
     })
   })
+
+  describe('UseEffects', () => {
+    let actions$:Observable<any>
+
+    beforeEach(() => {  
+      TestBed.configureTestingModule({
+        providers: [
+          UseEffects,
+          provideMockActions(() => actions$),
+          provideMockStore({ initialState: defaultRootState })
+        ]
+      })
+
+      const useEffectsInstance: UseEffects = TestBed.get(UseEffects)
+      useEffectsInstance.onParcellationSelected$.subscribe(console.log)
+
+    })
+
+    it('both SELECT_PARCELLATION and NEWVIEWER actions should trigger onParcellationSelected$', () => {
+      const useEffectsInstance: UseEffects = TestBed.get(UseEffects)
+      actions$ = hot(
+        'ab',
+        {
+          a: { type: SELECT_PARCELLATION },
+          b: { type: NEWVIEWER }
+        }
+      )
+      expect(
+        useEffectsInstance.onParcellationSelected$
+      ).toBeObservable(
+        hot(
+          'aa',
+          {
+            a: { type: SELECT_REGIONS, selectRegions: [] }
+          }  
+        )
+      )
+    })
+  })
 })