src/app/util/events/events.util.spec.ts

/********************************************************************************
 * Copyright (c) 2020 Contributors to the Eclipse Foundation
 *
 * See the NOTICE file(s) distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0
 *
 * SPDX-License-Identifier: EPL-2.0
 ********************************************************************************/

import {fromReturningToBrowserTabEvent} from "./events.util";

describe("EventsUtil", () => {

    it("should create an Observable which listens to events when returning to the browser tab", () => {
        const mockedDocument = new MockDocument(document);

        let hasFired = 0;
        let error: any = null;
        let hasFinished = false;

        const subscription = fromReturningToBrowserTabEvent(mockedDocument.asDocument)
            .subscribe((e) => hasFired++, (err) => error = err, () => hasFinished = true);

        expect(hasFired).toBe(0);
        expect(error != null).toBeFalse();
        expect(hasFinished).toBeFalse();

        mockedDocument.setToHidden();
        mockedDocument.dispatchVisibilityChangeEvent();

        expect(hasFired).toBe(0);
        expect(error != null).toBeFalse();
        expect(hasFinished).toBeFalse();

        mockedDocument.setToVisible();
        mockedDocument.dispatchVisibilityChangeEvent();

        expect(hasFired).toBe(1);
        expect(error != null).toBeFalse();
        expect(hasFinished).toBeFalse();

        subscription.unsubscribe();
    });

});

/**
 * Mocking class for document to set the visiblity status and dispatch events
 */
class MockDocument {

    public constructor(public readonly document: Document) {

    }

    public _visibilityState: "hidden" | "visible" = "hidden";

    public get visibilityState() {
        return this._visibilityState;
    }

    public get asDocument(): Document {
        return this as any as Document;
    }

    public setToVisible() {
        this._visibilityState = "visible";
    }

    // Mocked Properties and Methods:

    public setToHidden() {
        this._visibilityState = "hidden";
    }

    public dispatchVisibilityChangeEvent() {
        const event = this.document.createEvent("Event");
        event.initEvent("visibilitychange", true, false);
        this.document.dispatchEvent(event);
    }

    public addEventListener(arg1, arg2, arg3?) {
        return this.document.addEventListener(arg1, arg2, arg3);
    }

    public removeEventListener(arg0, arg1, arg2?) {
        return this.document.removeEventListener(arg0, arg1, arg2);
    }

}