add developer tab snapshot test

src/settings/DeveloperSettingsTab.test.tsx

@@ -0,0 +1,95 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { describe, expect, it, vi } from "vitest";
+import { render, waitFor } from "@testing-library/react";
+
+import type { MatrixClient } from "matrix-js-sdk";
+import type { Room as LivekitRoom } from "livekit-client";
+import { DeveloperSettingsTab } from "./DeveloperSettingsTab";
+
+// Mock url params hook to avoid environment-dependent snapshot churn.
+vi.mock("../UrlParams", () => ({
+  useUrlParams: (): { mocked: boolean; answer: number } => ({
+    mocked: true,
+    answer: 42,
+  }),
+}));
+
+// Provide a minimal mock of a Livekit Room structure used by the component.
+function createMockLivekitRoom(
+  wsUrl: string,
+  serverInfo: object,
+  metadata: string,
+): { isLocal: boolean; url: string; room: LivekitRoom } {
+  const mockRoom = {
+    serverInfo,
+    metadata,
+    engine: { client: { ws: { url: wsUrl } } },
+  } as unknown as LivekitRoom;
+
+  return {
+    isLocal: true,
+    url: wsUrl,
+    room: mockRoom,
+  };
+}
+
+// Minimal MatrixClient mock with only the methods used by the component.
+function createMockMatrixClient(): MatrixClient {
+  return {
+    doesServerSupportUnstableFeature: vi.fn().mockResolvedValue(true), // ensure stickyEventsSupported eventually becomes true
+    getCrypto: (): { getVersion: () => string } | undefined => ({
+      getVersion: () => "crypto-1.0.0",
+    }),
+    getUserId: () => "@alice:example.org",
+    getDeviceId: () => "DEVICE123",
+  } as unknown as MatrixClient;
+}
+
+describe("DeveloperSettingsTab", () => {
+  it("renders and matches snapshot", async () => {
+    const client = createMockMatrixClient();
+
+    const livekitRooms: {
+      room: LivekitRoom;
+      url: string;
+      isLocal?: boolean;
+    }[] = [
+      createMockLivekitRoom(
+        "wss://local-sfu.example.org",
+        { region: "local", version: "1.2.3" },
+        "local-metadata",
+      ),
+      {
+        isLocal: false,
+        url: "wss://remote-sfu.example.org",
+        room: {
+          serverInfo: { region: "remote", version: "4.5.6" },
+          metadata: "remote-metadata",
+          engine: { client: { ws: { url: "wss://remote-sfu.example.org" } } },
+        } as unknown as LivekitRoom,
+      },
+    ];
+
+    const { container } = render(
+      <DeveloperSettingsTab
+        client={client}
+        livekitRooms={livekitRooms}
+        env={{ MY_MOCK_ENV: 10, ENV: "test" } as unknown as ImportMetaEnv}
+      />,
+    );
+
+    // Wait for the async sticky events feature check to resolve so the final UI
+    // (e.g. enabled Matrix_2_0 radio button) appears deterministically.
+    await waitFor(() =>
+      expect(client.doesServerSupportUnstableFeature).toHaveBeenCalled(),
+    );
+
+    expect(container).toMatchSnapshot();
+  });
+});