diff --git a/src/app/core/shared/operators.ts b/src/app/core/shared/operators.ts
index dd610b6ca7..5cef7e5e09 100644
--- a/src/app/core/shared/operators.ts
+++ b/src/app/core/shared/operators.ts
@@ -1,6 +1,6 @@
 import { Router, UrlTree } from '@angular/router';
 import { combineLatest as observableCombineLatest, Observable } from 'rxjs';
-import { filter, find, map, mergeMap, switchMap, take, takeWhile, tap } from 'rxjs/operators';
+import { debounceTime, filter, find, map, mergeMap, switchMap, take, takeWhile, tap } from 'rxjs/operators';
 import { hasNoValue, hasValue, hasValueOperator, isNotEmpty } from '../../shared/empty.util';
 import { SearchResult } from '../../shared/search/search-result.model';
 import { PaginatedList } from '../data/paginated-list.model';
@@ -15,6 +15,12 @@ import { DSpaceObject } from './dspace-object.model';
 import { getForbiddenRoute, getPageNotFoundRoute } from '../../app-routing-paths';
 import { getEndUserAgreementPath } from '../../info/info-routing-paths';
 import { AuthService } from '../auth/auth.service';
+import { InjectionToken } from '@angular/core';
+
+export const DEBOUNCE_TIME_OPERATOR = new InjectionToken<<T>(dueTime: number) => (source: Observable<T>) => Observable<T>>('debounceTime', {
+  providedIn: 'root',
+  factory: () => debounceTime
+});
 
 /**
  * This file contains custom RxJS operators that can be used in multiple places
diff --git a/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/relationship.effects.spec.ts b/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/relationship.effects.spec.ts
index 5e2ffd30fb..e988eba9eb 100644
--- a/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/relationship.effects.spec.ts
+++ b/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/relationship.effects.spec.ts
@@ -1,10 +1,7 @@
 import { TestBed, waitForAsync } from '@angular/core/testing';
-
 import { BehaviorSubject, Observable, of as observableOf } from 'rxjs';
-import { TestScheduler } from 'rxjs/testing';
 import { provideMockActions } from '@ngrx/effects/testing';
 import { Store } from '@ngrx/store';
-
 import { RelationshipEffects } from './relationship.effects';
 import { AddRelationshipAction, RelationshipActionTypes, RemoveRelationshipAction } from './relationship.actions';
 import { Item } from '../../../../../core/shared/item.model';
@@ -23,6 +20,9 @@ import { RequestService } from '../../../../../core/data/request.service';
 import { NotificationsService } from '../../../../notifications/notifications.service';
 import { TranslateService } from '@ngx-translate/core';
 import { SelectableListService } from '../../../../object-list/selectable-list/selectable-list.service';
+import { cold, hot } from 'jasmine-marbles';
+import { DEBOUNCE_TIME_OPERATOR } from '../../../../../core/shared/operators';
+import { last } from 'rxjs/operators';
 
 describe('RelationshipEffects', () => {
   let relationEffects: RelationshipEffects;
@@ -51,7 +51,6 @@ describe('RelationshipEffects', () => {
   let notificationsService;
   let translateService;
   let selectableListService;
-  let testScheduler: TestScheduler;
 
   function init() {
     testUUID1 = '20e24c2f-a00a-467c-bdee-c929e79bf08d';
@@ -131,6 +130,7 @@ describe('RelationshipEffects', () => {
         { provide: NotificationsService, useValue: notificationsService },
         { provide: TranslateService, useValue: translateService },
         { provide: SelectableListService, useValue: selectableListService },
+        { provide: DEBOUNCE_TIME_OPERATOR, useValue: jasmine.createSpy('debounceTime').and.returnValue((v) => v.pipe(last())) },
       ],
     });
   }));
@@ -140,9 +140,6 @@ describe('RelationshipEffects', () => {
     identifier = (relationEffects as any).createIdentifier(leftItem, rightItem, relationshipType.leftwardType);
     spyOn((relationEffects as any), 'addRelationship').and.stub();
     spyOn((relationEffects as any), 'removeRelationship').and.stub();
-    testScheduler = new TestScheduler((actual, expected) => {
-      expect(actual).toEqual(expected);
-    });
   });
 
   describe('mapLastActions$', () => {
@@ -151,15 +148,13 @@ describe('RelationshipEffects', () => {
         let action;
 
         it('should set the current value debounceMap and the value of the initialActionMap to ADD_RELATIONSHIP', () => {
-          testScheduler.run(({ hot, expectObservable, flush }) => {
-            action = new AddRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
-            actions = hot('--a-|', { a: action });
-            expectObservable(relationEffects.mapLastActions$).toBe('--b-|', { b: undefined });
-            flush();
-            // TODO check following expectations with the implementation
-            // expect((relationEffects as any).initialActionMap[identifier]).toBe(action.type);
-            // expect((relationEffects as any).debounceMap[identifier].value).toBe(action.type);
-          });
+          action = new AddRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
+          actions = hot('--a-|', { a: action });
+          const expected = cold('--b-|', { b: undefined });
+          expect(relationEffects.mapLastActions$).toBeObservable(expected);
+
+          expect((relationEffects as any).initialActionMap[identifier]).toBe(action.type);
+          expect((relationEffects as any).debounceMap[identifier].value).toBe(action.type);
         });
       });
 
@@ -172,14 +167,14 @@ describe('RelationshipEffects', () => {
         });
 
         it('should set the current value debounceMap to ADD_RELATIONSHIP but not change the value of the initialActionMap', () => {
-          testScheduler.run(({ hot, expectObservable, flush }) => {
-            action = new AddRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
-            actions = hot('--a-|', { a: action });
-            expectObservable(relationEffects.mapLastActions$).toBe('--b-|', { b: undefined });
-            flush();
-            expect((relationEffects as any).initialActionMap[identifier]).toBe(testActionType);
-            expect((relationEffects as any).debounceMap[identifier].value).toBe(action.type);
-          });
+          action = new AddRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
+          actions = hot('--a-|', { a: action });
+
+          const expected = cold('--b-|', { b: undefined });
+          expect(relationEffects.mapLastActions$).toBeObservable(expected);
+
+          expect((relationEffects as any).initialActionMap[identifier]).toBe(testActionType);
+          expect((relationEffects as any).debounceMap[identifier].value).toBe(action.type);
         });
       });
 
@@ -188,30 +183,26 @@ describe('RelationshipEffects', () => {
         describe('When the last value in the debounceMap is also an ADD_RELATIONSHIP action', () => {
           beforeEach(() => {
             (relationEffects as any).initialActionMap[identifier] = RelationshipActionTypes.ADD_RELATIONSHIP;
+            ((relationEffects as any).debounceTime as jasmine.Spy).and.returnValue((v) => v);
           });
           it('should call addRelationship on the effect', () => {
-            testScheduler.run(({ hot, expectObservable, flush }) => {
-              action = new AddRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
-              actions = hot('--a-|', { a: action });
-              expectObservable(relationEffects.mapLastActions$).toBe('--b-|', { b: undefined });
-              flush();
-              expect((relationEffects as any).addRelationship).toHaveBeenCalledWith(leftItem, rightItem, relationshipType.leftwardType, '1234', undefined);
-            });
+            action = new AddRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
+            actions = hot('--a-|', { a: action });
+            const expected = cold('--b-|', { b: undefined });
+            expect(relationEffects.mapLastActions$).toBeObservable(expected);
+            expect((relationEffects as any).addRelationship).toHaveBeenCalledWith(leftItem, rightItem, relationshipType.leftwardType, '1234', undefined);
           });
         });
 
         describe('When the last value in the debounceMap is instead a REMOVE_RELATIONSHIP action', () => {
-
           it('should <b>not</b> call removeRelationship or addRelationship on the effect', () => {
-            testScheduler.run(({ hot, expectObservable, flush }) => {
-              const actiona = new AddRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
-              const actionb = new RemoveRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
-              actions = hot('--ab-|', { a: actiona, b: actionb });
-              expectObservable(relationEffects.mapLastActions$).toBe('--bb-|', { b: undefined });
-              flush();
-              expect((relationEffects as any).addRelationship).not.toHaveBeenCalled();
-              expect((relationEffects as any).removeRelationship).not.toHaveBeenCalled();
-            });
+            const actiona = new AddRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
+            const actionb = new RemoveRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
+            actions = hot('--ab-|', { a: actiona, b: actionb });
+            const expected = cold('--bb-|', { b: undefined });
+            expect(relationEffects.mapLastActions$).toBeObservable(expected);
+            expect((relationEffects as any).addRelationship).not.toHaveBeenCalled();
+            expect((relationEffects as any).removeRelationship).not.toHaveBeenCalled();
           });
         });
       });
@@ -222,15 +213,13 @@ describe('RelationshipEffects', () => {
         let action;
 
         it('should set the current value debounceMap and the value of the initialActionMap to REMOVE_RELATIONSHIP', () => {
-          testScheduler.run(({ hot, expectObservable, flush }) => {
-            action = new RemoveRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
-            actions = hot('--a-|', { a: action });
-            expectObservable(relationEffects.mapLastActions$).toBe('--b-|', { b: undefined });
-            flush();
-            // TODO check following expectations with the implementation
-            // expect((relationEffects as any).initialActionMap[identifier]).toBe(action.type);
-            // expect((relationEffects as any).debounceMap[identifier].value).toBe(action.type);
-          });
+          action = new RemoveRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
+          actions = hot('--a-|', { a: action });
+          const expected = cold('--b-|', { b: undefined });
+          expect(relationEffects.mapLastActions$).toBeObservable(expected);
+
+          expect((relationEffects as any).initialActionMap[identifier]).toBe(action.type);
+          expect((relationEffects as any).debounceMap[identifier].value).toBe(action.type);
         });
       });
 
@@ -238,20 +227,19 @@ describe('RelationshipEffects', () => {
         let action;
         const testActionType = 'TEST_TYPE';
         beforeEach(() => {
+          ((relationEffects as any).debounceTime as jasmine.Spy).and.returnValue((v) => v);
           (relationEffects as any).initialActionMap[identifier] = testActionType;
           (relationEffects as any).debounceMap[identifier] = new BehaviorSubject<string>(testActionType);
         });
 
         it('should set the current value debounceMap to REMOVE_RELATIONSHIP but not change the value of the initialActionMap', () => {
-          testScheduler.run(({ hot, expectObservable, flush }) => {
-            action = new RemoveRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
-            actions = hot('--a-|', { a: action });
-            expectObservable(relationEffects.mapLastActions$).toBe('--b-|', { b: undefined });
-            flush();
-            // TODO check following expectations with the implementation
-            // expect((relationEffects as any).initialActionMap[identifier]).toBe(testActionType);
-            // expect((relationEffects as any).debounceMap[identifier].value).toBe(action.type);
-          });
+          action = new RemoveRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
+          actions = hot('--a-|', { a: action });
+          const expected = cold('--b-|', { b: undefined });
+          expect(relationEffects.mapLastActions$).toBeObservable(expected);
+
+          expect((relationEffects as any).initialActionMap[identifier]).toBe(testActionType);
+          expect((relationEffects as any).debounceMap[identifier].value).toBe(action.type);
         });
       });
 
@@ -259,32 +247,28 @@ describe('RelationshipEffects', () => {
         let action;
         describe('When the last value in the debounceMap is also an REMOVE_RELATIONSHIP action', () => {
           beforeEach(() => {
+            ((relationEffects as any).debounceTime as jasmine.Spy).and.returnValue((v) => v);
             (relationEffects as any).initialActionMap[identifier] = RelationshipActionTypes.REMOVE_RELATIONSHIP;
           });
 
           it('should call removeRelationship on the effect', () => {
-            testScheduler.run(({ hot, expectObservable, flush }) => {
-              action = new RemoveRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
-              actions = hot('a', { a: action });
-              expectObservable(relationEffects.mapLastActions$).toBe('b', { b: undefined });
-              flush();
-              expect((relationEffects as any).removeRelationship).toHaveBeenCalledWith(leftItem, rightItem, relationshipType.leftwardType, '1234',);
-            });
+            action = new RemoveRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
+            actions = hot('--a-|', { a: action });
+            const expected = cold('--b-|', { b: undefined });
+            expect(relationEffects.mapLastActions$).toBeObservable(expected);
+            expect((relationEffects as any).removeRelationship).toHaveBeenCalledWith(leftItem, rightItem, relationshipType.leftwardType, '1234',);
           });
         });
 
         describe('When the last value in the debounceMap is instead a ADD_RELATIONSHIP action', () => {
-
           it('should <b>not</b> call addRelationship or removeRelationship on the effect', () => {
-            testScheduler.run(({ hot, expectObservable, flush }) => {
-              const actionb = new RemoveRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
-              const actiona = new AddRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
-              actions = hot('--ab-|', { a: actiona, b: actionb });
-              expectObservable(relationEffects.mapLastActions$).toBe('--bb-|', { b: undefined });
-              flush();
-              expect((relationEffects as any).addRelationship).not.toHaveBeenCalled();
-              expect((relationEffects as any).removeRelationship).not.toHaveBeenCalled();
-            });
+            const actionb = new RemoveRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
+            const actiona = new AddRelationshipAction(leftItem, rightItem, relationshipType.leftwardType, '1234');
+            actions = hot('--ab-|', { a: actiona, b: actionb });
+            const expected = cold('--bb-|', { b: undefined });
+            expect(relationEffects.mapLastActions$).toBeObservable(expected);
+            expect((relationEffects as any).addRelationship).not.toHaveBeenCalled();
+            expect((relationEffects as any).removeRelationship).not.toHaveBeenCalled();
           });
         });
       });
diff --git a/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/relationship.effects.ts b/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/relationship.effects.ts
index 5a20ed8b51..a810cb0ad9 100644
--- a/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/relationship.effects.ts
+++ b/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/relationship.effects.ts
@@ -1,11 +1,11 @@
-import { Injectable } from '@angular/core';
+import { Inject, Injectable } from '@angular/core';
 import { Actions, Effect, ofType } from '@ngrx/effects';
-import { debounceTime, filter, map, mergeMap, switchMap, take } from 'rxjs/operators';
+import { filter, map, mergeMap, switchMap, take } from 'rxjs/operators';
 import { BehaviorSubject, Observable } from 'rxjs';
 import { RelationshipService } from '../../../../../core/data/relationship.service';
 import {
   getRemoteDataPayload,
-  getFirstSucceededRemoteData
+  getFirstSucceededRemoteData, DEBOUNCE_TIME_OPERATOR
 } from '../../../../../core/shared/operators';
 import {
   AddRelationshipAction,
@@ -71,7 +71,7 @@ export class RelationshipEffects {
             this.initialActionMap[identifier] = action.type;
             this.debounceMap[identifier] = new BehaviorSubject<string>(action.type);
             this.debounceMap[identifier].pipe(
-              debounceTime(DEBOUNCE_TIME),
+              this.debounceTime(DEBOUNCE_TIME),
               take(1)
             ).subscribe(
               (type) => {
@@ -159,6 +159,7 @@ export class RelationshipEffects {
               private notificationsService: NotificationsService,
               private translateService: TranslateService,
               private selectableListService: SelectableListService,
+              @Inject(DEBOUNCE_TIME_OPERATOR) private debounceTime: <T>(dueTime: number) => (source: Observable<T>) => Observable<T>,
   ) {
   }