I have a hard time getting my unit test to work together with an Observable with delay operator. The application is built on Angular 2 and the tests are running in karma/jasmine. I've tried the async and fakeAsync helper methods but none of them are working.
Here's a simplified code block (without Angular 2) explaining my issue.
let mouseDownStream = Rx.Observable.fromEvent(document.body, 'mousedown');
let haveBeenCalled = false;
mouseDownStream.delay(200).subscribe(() => haveBeenCalled = true);
describe('mouse down event', () => {
it('it should emit an event stream after 200ms', (done) => {
document.body.dispatchEvent(new MouseEvent('mousedown'))
expect(haveBeenCalled).toBeFalsy();
// Don't want this setTimeout should use Angular's tick(200) method instead but it's not working.
setTimeout(() => {
expect(haveBeenCalled).toBeTruthy();
done();
}, 200)
});
});
Here is an example on how to unit test an Observable with a delay operator in Angular 2+, should anyone still be looking for the answer:
import { fakeAsync, tick } from "@angular/core/testing";
import { fromEvent } from "rxjs";
import { delay } from "rxjs/operators";
describe("mouse down event", () => {
it("should emit an event stream after 200ms", fakeAsync(() => {
let mouseDownStream = fromEvent(document.body, "mousedown");
let haveBeenCalled = false;
const subscription = mouseDownStream.pipe(delay(200)).subscribe(() => (haveBeenCalled = true));
document.body.dispatchEvent(new MouseEvent("mousedown"));
expect(haveBeenCalled).toBeFalsy();
tick(200);
expect(haveBeenCalled).toBeTruthy();
subscription.unsubscribe();
}));
});
Using rxjs 6 with angular 12, fakeAsync doesn't work for me. Only using the TestScheduler did. Modifying Ritchie's sample:
describe("mouse down event", () => {
let testScheduler: TestScheduler;
beforeEach(() => {
testScheduler = new TestScheduler((act, exp) => expect(exp).toEqual(act) as any);
});
fit("should emit an event stream after 200ms", () => {
let mouseDownStream = fromEvent(document.body, "mousedown");
let haveBeenCalled = false;
testScheduler.run(() => {
const subscription = mouseDownStream.pipe(delay(200)).subscribe(() => (haveBeenCalled = true));
document.body.dispatchEvent(new MouseEvent("mousedown"));
expect(haveBeenCalled).toBeFalsy();
testScheduler.createTime('200|');
testScheduler.flush();
expect(haveBeenCalled).toBeTruthy();
subscription.unsubscribe();
});
});
});