diff --git a/src/app/datapoints-graph/charts/custom-measurements.service.spec.ts b/src/app/datapoints-graph/charts/custom-measurements.service.spec.ts
index 614ad53d..d517bd45 100644
--- a/src/app/datapoints-graph/charts/custom-measurements.service.spec.ts
+++ b/src/app/datapoints-graph/charts/custom-measurements.service.spec.ts
@@ -1,6 +1,7 @@
 import { fakeAsync, TestBed, tick } from '@angular/core/testing';
 import { FetchClient, ISeries, Realtime } from '@c8y/client';
 import { ApiService } from '@c8y/ngx-components/api';
+import { firstValueFrom } from 'rxjs';
 import { CustomMeasurementService } from './custom-measurements.service';
 
 describe('CustomMeasurementService', () => {
@@ -26,17 +27,20 @@ describe('CustomMeasurementService', () => {
         .mockName('getFetchOptions')
         .mockReturnValue(options),
       getUrl: jest.fn().mockName('getFetchOptions').mockReturnValue(fullUrl),
-      fetch: jest.fn().mockName('fetch').mockImplementation(),
+      fetch: jest
+        .fn()
+        .mockName('fetch')
+        .mockImplementation(() => Promise.resolve(response)),
     } as any as FetchClient;
     TestBed.configureTestingModule({
       providers: [
-        CustomMeasurementService,
         { provide: FetchClient, useValue: client },
         { provide: Realtime, useValue: {} },
         {
           provide: ApiService,
           useValue: apiService,
         },
+        CustomMeasurementService,
       ],
     });
     service = TestBed.inject(CustomMeasurementService);
@@ -61,23 +65,19 @@ describe('CustomMeasurementService', () => {
     });
   }));
 
-  it('should call onFinish to trigger header loading bar', fakeAsync(() => {
-    // when
-    (global as any).fetch = jest
-      .fn()
-      .mockImplementationOnce(() => Promise.resolve(response));
-    service.listSeries$({} as any).subscribe();
-    tick();
-    // then
+  it('should call onFinish to trigger header loading bar', async () => {
+    (global as any).fetch = jest.fn().mockResolvedValueOnce(response);
+
+    await firstValueFrom(service.listSeries$({} as any));
     expect(apiService.onFinish).toHaveBeenCalledWith({
-      options,
       method: 'GET',
-      url: '/measurement/measurements/series',
+      options,
       response,
+      url: '/measurement/measurements/series',
     });
-  }));
+  });
 
-  it('should return resolved data', fakeAsync(() => {
+  it('should return resolved data', (done) => {
     // when
     const values = { [new Date().toString()]: [{ min: 0, max: 1 }] };
     (global as any).fetch = jest.fn().mockImplementationOnce(() =>
@@ -85,12 +85,9 @@ describe('CustomMeasurementService', () => {
         json: () => ({ values } as ISeries),
       })
     );
-    let resolvedData;
-    service
-      .listSeries$({} as any)
-      .subscribe((val) => (resolvedData = val.data));
-    tick();
-    // then
-    expect(resolvedData.values).toEqual(values);
-  }));
+    service.listSeries$({} as any).subscribe((val) => {
+      expect(val.data.values).toEqual(values);
+      done();
+    });
+  });
 });
diff --git a/src/app/datapoints-graph/charts/custom-measurements.service.ts b/src/app/datapoints-graph/charts/custom-measurements.service.ts
index 15d631f3..4d3fd6be 100644
--- a/src/app/datapoints-graph/charts/custom-measurements.service.ts
+++ b/src/app/datapoints-graph/charts/custom-measurements.service.ts
@@ -17,10 +17,12 @@ import { cloneDeep } from 'lodash-es';
 
 @Injectable()
 export class CustomMeasurementService extends MeasurementService {
-  apiService: ApiService;
-  constructor(client: FetchClient, realtime: Realtime, apiService: ApiService) {
+  constructor(
+    client: FetchClient,
+    realtime: Realtime,
+    private apiService: ApiService
+  ) {
     super(client, realtime);
-    this.apiService = apiService;
   }
 
   listSeries$(params: ISeriesFilter): Observable<IResult<ISeries>> {
@@ -50,6 +52,7 @@ export class CustomMeasurementService extends MeasurementService {
       switchMap(async (res) => {
         callOnFinish.response = res;
         const data = await res.json();
+
         return { res: res as IFetchResponse, data };
       }),
       finalize(() => {