feat(testing): add register test

test/register.test.ts

@@ -0,0 +1,43 @@
+import { JSDOM } from "jsdom"
+import { registerServiceWorker } from "../src/browser/register"
+const { window } = new JSDOM()
+global.window = (window as unknown) as Window & typeof globalThis
+global.document = window.document
+global.navigator = window.navigator
+
+describe("register", () => {
+  const spy = jest.fn()
+  beforeAll(() => {
+    // register relies on navigator to be defined globally
+    // this is because the code is called on the browser
+    // so we're sure it will be defined
+    // We have to cast/assert so that TS thinks it's the correct type
+    Object.defineProperty(global.navigator, "serviceWorker", {
+      value: {
+        register: spy,
+      },
+    })
+    // global.navigator.serviceWorker.register = (spy as unknown) as ServiceWorkerContainer["register"]
+  })
+
+  afterEach(() => {
+    jest.resetAllMocks()
+  })
+
+  afterAll(() => {
+    jest.restoreAllMocks()
+  })
+  it("should register a ServiceWorker", () => {
+    // call registerServiceWorker
+    const path = "/hello"
+    const mockOptions = {
+      base: "",
+      csStaticBase: "",
+      logLevel: 0,
+    }
+    registerServiceWorker(navigator, path, mockOptions)
+    // expect spy to have been called
+    expect(spy).toHaveBeenCalled()
+    expect(spy).toHaveBeenCalledTimes(1)
+  })
+})