test(Bar): add snapshot tests

frontend/__tests__/unit/components/Bar.test.jsx

@@ -0,0 +1,47 @@
+import { render } from "@testing-library/react";
+import Bar from "components/Bar";
+import { Router } from "react-router-dom";
+import { createMemoryHistory } from "history";
+
+// Useful reference: https://bholmes.dev/blog/mocking-browser-apis-fetch-localstorage-dates-the-easy-way-with-jest/
+
+let mockStorage = {};
+
+describe("Bar", () => {
+  beforeAll(() => {
+    global.Storage.prototype.getItem = jest.fn((key) => mockStorage[key]);
+  });
+
+  beforeEach(() => {
+    // make sure the fridge starts out empty for each test
+    mockStorage = {};
+  });
+
+  afterAll(() => {
+    global.Storage.prototype.getItem.mockReset();
+  });
+
+  it("renders Bar unchanged when logged out", () => {
+    const history = createMemoryHistory();
+    mockStorage["loggedIn"] = false;
+
+    const { container } = render(
+      <Router history={history}>
+        <Bar />
+      </Router>
+    );
+    expect(container).toMatchSnapshot();
+  });
+
+  it("renders Bar unchanged when logged in", () => {
+    const history = createMemoryHistory();
+    mockStorage["loggedIn"] = true;
+
+    const { container } = render(
+      <Router history={history}>
+        <Bar />
+      </Router>
+    );
+    expect(container).toMatchSnapshot();
+  });
+});