Event Mocking

Problem

You want to to work with web-extension events, but you don't want to expect calls to addListener and removeListener all the time.

Solution

my-events.spec.ts

import { mockEvent, MockzillaEventOf } from "mockzilla-webextension";

describe("MyEventHandler", () => {
    let myEventHandler: MyEventHandler;
    let onRemoved: MockzillaEventOf<typeof mockBrowser.tabs.onRemoved>;
    let onCreated: MockzillaEventOf<typeof mockBrowser.tabs.onCreated>;

    beforeEach(() => {
        onRemoved = mockEvent(mockBrowser.tabs.onRemoved);
        onCreated = mockEvent(mockBrowser.tabs.onCreated);
        myEventHandler = new MyEventHandler();
    });

    describe("listeners", () => {
        it("should add listeners after init", () => {
            myEventHandler.init();
            expect(onRemoved.hasListener(myEventHandler!["onTabRemoved"])).toBe(true);
            expect(onCreated.hasListener(myEventHandler!["onTabCreated"])).toBe(true);
        });
    });
    describe("onTabCreated", () => {
        it("do stuff with new tab", () => {
            myEventHandler.init();

            // ...

            onTabCreated.emit({
                active: true,
                cookieStoreId: "default",
                highlighted: false,
                id: 12,
                incognito: true,
                index: 1,
                isArticle: false,
                isInReaderMode: false,
                lastAccessed: Date.now(),
                pinned: false,
                url: "http://some-domain.com",
                windowId: 1,
            });
            // ...
        });
    });
});

The implementations of addListener, removeListener, hasListener and hasListeners are instances of jest.fn(), so you can use them to verify calls.