UnhandledPromiseRejectionWarning: TypeError: Converting circular structure to JSON with Jest + Angular

Question

Using the jest-preset-angular to perform the unit test, but got an warning as UnhandledPromiseRejectionWarning: TypeError: Converting circular structure to JSON not sure what causing the error, due to this the application is stuck and not running the other unit test.

PASS  src/app/pages/result/result-filter/result-filter.component.spec.ts (6.251 s)
 PASS  src/app/pages/result/search-navigation/search-navigation.component.spec.ts
 PASS  src/app/pages/result/filter-modal/filter-modal.component.spec.ts (5.699 s)
 PASS  src/app/app.component.spec.ts
 PASS  src/app/pages/test-type/test-type.component.spec.ts (12.857 s)
(node:3280) UnhandledPromiseRejectionWarning: TypeError: Converting circular structure to JSON
    --> starting at object with constructor 'Object'
    |     property 'element' -> object with constructor 'Object'
    |     property 'componentProvider' -> object with constructor 'Object'
    --- property 'parent' closes the circle
    at stringify (<anonymous>)
    at writeChannelMessage (internal/child_process/serialization.js:117:20)
    at process.target._send (internal/child_process.js:808:17)
    at process.target.send (internal/child_process.js:706:19)
    at reportSuccess (/Users/macbook/Projects/Playtime Projects/IDP/Idp.Bx.Ui/idp/node_modules/jest-worker/build/workers/processChild.js:67:11)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:3280) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:3280) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
(node:3281) UnhandledPromiseRejectionWarning: TypeError: Converting circular structure to JSON
    --> starting at object with constructor 'Object'
    |     property 'element' -> object with constructor 'Object'
    |     property 'componentProvider' -> object with constructor 'Object'
    --- property 'parent' closes the circle
    at stringify (<anonymous>)
    at writeChannelMessage (internal/child_process/serialization.js:117:20)
    at process.target._send (internal/child_process.js:808:17)
    at process.target.send (internal/child_process.js:706:19)
    at reportSuccess (/Users/macbook/Projects/Playtime Projects/IDP/Idp.Bx.Ui/idp/node_modules/jest-worker/build/workers/processChild.js:67:11)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:3281) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:3281) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
(node:3279) UnhandledPromiseRejectionWarning: TypeError: Converting circular structure to JSON
    --> starting at object with constructor 'Object'
    |     property 'element' -> object with constructor 'Object'
    |     property 'componentProvider' -> object with constructor 'Object'
    --- property 'parent' closes the circle
    at stringify (<anonymous>)
    at writeChannelMessage (internal/child_process/serialization.js:117:20)
    at process.target._send (internal/child_process.js:808:17)
    at process.target.send (internal/child_process.js:706:19)
    at reportSuccess (/Users/macbook/Projects/Playtime Projects/IDP/Idp.Bx.Ui/idp/node_modules/jest-worker/build/workers/processChild.js:67:11)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:3279) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:3279) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

 RUNS  src/app/pages/location/location.component.spec.ts
 RUNS  src/app/pages/signup/signup.component.spec.ts
 RUNS  src/app/pages/login/login.component.spec.ts

Test Suites: 10 passed, 10 of 20 total
Tests:       16 passed, 16 total
Snapshots:   1 obsolete, 5 passed, 5 total
Time:        2180 s

I am not sure how to run the node --trace-warnings. Looks like it a serialization issue, even it is just a warning but not sure where is the issue. Is there any better way to find the exception

I have a similar issue and I believe in my case it's related with the fact that I am doing some async work in ngOnInit. — bboydflo, Sep 16 '20 at 11:31
In my case its an observable (say, this.observeMe$) in ngOnInit function being awaited in the html file (say, {{ observeMe | async }}) I changed it to this.observeMe.subscribe(...) to overcome this issue. — Beniston, Oct 15 '20 at 05:56
https://stackoverflow.com/questions/11616630/how-can-i-print-a-circular-structure-in-a-json-like-format shows how to use JSON to a circular so it at least should solve your error — The Bomb Squad, Nov 30 '20 at 23:23

James Barrett · Answer 1 · 2021-06-09T14:09:29.397

117

Run jest with --detectOpenHandles. This will show you what is actually wrong with your test spec. For me, there were missing Angular Material imports and service mocks. You may be prompted to add the BrowserAnimationsModule, as Nambi alluded to in his answer

package.json:

"test": "jest --detectOpenHandles"

edited Jun 09 '21 at 14:09

answered Nov 30 '20 at 22:32

James Barrett

2,757
4
25
35

score 21 · Answer 2 · answered Jun 08 '21 at 11:02

This message usually appears, if there is an error, that does not resolve into a standard exception.

As mentioned by @JamesBarret using jests detect open handle feature will provide you with a nice error message, telling you what the real problem behind this message is.

The handle --detectOpenHandles mentioned in the other message is deprecated though and was replaced with --detect-open-handles.

You can just use: (on your cli)

jest --detect-open-handles

Or in a package.json file:

"test": "jest --detect-open-handles"

Or as it was in my case an angular test:

ng test --detect-open-handles

score 2 · Answer 3 · answered Nov 17 '20 at 06:33

2

Adding my answer to help someone if missed. In my case i have missed to import

import { BrowserAnimationsModule } from '@angular/platform-browser/animations';

Able to find the issue only when running one of the test case in isolation.

answered Nov 17 '20 at 06:33

Nambi N Rajan

491
5
15

score 0 · Answer 4 · answered Oct 12 '20 at 02:26

The issue was with the async operation, so writing the test case with below, solve the issue for me

describe('DateSelectionComponent', () => {
  let component: DateSelectionComponent;
  let fixture: ComponentFixture<DateSelectionComponent>;

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [DateSelectionComponent, SafePipe],
      imports: [
        SharedModule,
        NgReduxTestingModule,
        RouterTestingModule.withRoutes([])
      ],
      providers: [
        {
          provide: PageAPIActions, useValue: { setPageState() { } }
        }
      ]
    }).compileComponents();
    fixture = TestBed.createComponent(DateSelectionComponent);
    component = fixture.componentInstance;

    // Don't use Object.defineProperty when assigning value to class properties
    component.page$ = of('value');
    component.page = { destination: 'value' };
    component.startDate = new NgbDate(2019, 2, 27);
    component.minDate = new NgbDate(2019, 2, 27);
    fixture.detectChanges();
  }));

  it('should create', () => {
    expect(component).toBeTruthy();
  });

  it('Should Match Snapshot', () => {
     expect(fixture.debugElement.nativeElement).toMatchSnapshot()
  });
});

score 0 · Answer 5 · answered Oct 23 '20 at 16:04

0

In my situation, the cryptic error was triggered by not importing HttpClientModule into the test file. More details here.

answered Oct 23 '20 at 16:04

Avi Kaminetzky

1,489
2
19
42

score -1 · Answer 6 · answered Mar 25 '21 at 13:34

-1

I had this same issue when running jest with --watch. Removing --watch stopped the error.

answered Mar 25 '21 at 13:34

Brian McGough

17
1

score -2 · Answer 7 · answered Oct 06 '20 at 12:42

-2

Looks like the error is due to some async operation being done. Try wrapping your unit test inside a waitForAsync function.

answered Oct 06 '20 at 12:42

Anatolie Darii

5
2

UnhandledPromiseRejectionWarning: TypeError: Converting circular structure to JSON with Jest + Angular

7 Answers7