🧪 Add Vitest testing framework with basic composition test

Set up testing infrastructure using Vitest and React Testing Library.
Add test verifying empty MyComposition renders without errors.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

videos/package.json

@@ -20,18 +20,25 @@
   },
   "devDependencies": {
     "@remotion/eslint-config-flat": "4.0.409",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
     "@types/react": "19.2.7",
     "@types/three": "^0.182.0",
     "@types/web": "0.0.166",
+    "@vitejs/plugin-react": "^5.1.2",
     "eslint": "9.19.0",
+    "jsdom": "^27.4.0",
     "prettier": "3.6.0",
-    "typescript": "5.9.3"
+    "typescript": "5.9.3",
+    "vitest": "^4.0.18"
   },
   "scripts": {
     "dev": "remotion studio",
     "build": "remotion bundle",
     "upgrade": "remotion upgrade",
-    "lint": "eslint src && tsc"
+    "lint": "eslint src && tsc",
+    "test": "vitest run",
+    "test:watch": "vitest"
   },
   "sideEffects": [
     "*.css"

videos/src/Composition.test.tsx

@@ -0,0 +1,15 @@
+import { describe, it, expect } from "vitest";
+import { render } from "@testing-library/react";
+import { MyComposition } from "./Composition";
+
+describe("MyComposition", () => {
+  it("renders without errors", () => {
+    const { container } = render(<MyComposition />);
+    expect(container).toBeInTheDocument();
+  });
+
+  it("returns null (empty composition)", () => {
+    const { container } = render(<MyComposition />);
+    expect(container.firstChild).toBeNull();
+  });
+});

videos/src/test/setup.ts

@@ -0,0 +1 @@
+import "@testing-library/jest-dom/vitest";

videos/tsconfig.json

@@ -11,5 +11,5 @@
     "forceConsistentCasingInFileNames": true,
     "noUnusedLocals": true
   },
-  "exclude": ["remotion.config.ts"]
+  "exclude": ["remotion.config.ts", "vitest.config.ts"]
 }

videos/vitest.config.ts

@@ -0,0 +1,11 @@
+import { defineConfig } from "vitest/config";
+import react from "@vitejs/plugin-react";
+
+export default defineConfig({
+  plugins: [react()],
+  test: {
+    environment: "jsdom",
+    setupFiles: ["./src/test/setup.ts"],
+    include: ["src/**/*.test.{ts,tsx}"],
+  },
+});