Improve test coverage

src/AppBar.test.tsx

@@ -5,21 +5,33 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */
 
+import { type FC, type ReactNode } from "react";
 import { render } from "@testing-library/react";
 import { describe, expect, it } from "vitest";
 import { TooltipProvider } from "@vector-im/compound-web";
 
-import { AppBar } from "./AppBar";
+import { AppBar, useAppBarSubtitle, useAppBarTitle } from "./AppBar";
+
+const content = <p>This is the content.</p>;
+
+function snapshotAppBar(content: ReactNode): void {
+  const { container } = render(
+    <TooltipProvider>
+      <AppBar>{content}</AppBar>
+    </TooltipProvider>,
+  );
+  expect(container).toMatchSnapshot();
+}
 
 describe("AppBar", () => {
-  it("renders", () => {
-    const { container } = render(
-      <TooltipProvider>
-        <AppBar>
-          <p>This is the content.</p>
-        </AppBar>
-      </TooltipProvider>,
-    );
-    expect(container).toMatchSnapshot();
+  it("renders", () => snapshotAppBar(content));
+
+  it("renders with title and subtitle", () => {
+    const TestComponent: FC = () => {
+      useAppBarTitle("Title");
+      useAppBarSubtitle("Subtitle");
+      return content;
+    };
+    snapshotAppBar(<TestComponent />);
   });
 });