Error: Objects are not valid as a React child ...

[jay-linumlabs]

Description:
Integrating vitest with a fresh nextJS application results in the following error:

Error: Objects are not valid as a React child (found: object with keys {$$typeof, type, key, props, _owner, _store}). If you meant to render a collection of children, use an array instead.
 ❯ throwOnInvalidObjectType ../../node_modules/react-dom/cjs/react-dom.development.js:13123:9
 ❯ reconcileChildFibers ../../node_modules/react-dom/cjs/react-dom.development.js:14064:7
 ❯ reconcileChildren ../../node_modules/react-dom/cjs/react-dom.development.js:19193:28
 ❯ updateHostRoot ../../node_modules/react-dom/cjs/react-dom.development.js:19912:5
 ❯ beginWork ../../node_modules/react-dom/cjs/react-dom.development.js:21654:14
 ❯ beginWork$1 ../../node_modules/react-dom/cjs/react-dom.development.js:27465:14
 ❯ performUnitOfWork ../../node_modules/react-dom/cjs/react-dom.development.js:26599:12
 ❯ workLoopSync ../../node_modules/react-dom/cjs/react-dom.development.js:26505:5
 ❯ renderRootSync ../../node_modules/react-dom/cjs/react-dom.development.js:26473:7
 ❯ performConcurrentWorkOnRoot ../../node_modules/react-dom/cjs/react-dom.development.js:25777:74

This uses React 19.

If I downgrade to React 18 it works:

Working Screenshot:

Working package.json

{
  "name": "web",
  "version": "0.1.0",
  "private": true,
  "scripts": {
    "dev": "next dev --turbopack",
    "build": "next build",
    "start": "next start",
    "lint": "next lint",
    "check-types": "tsc --noEmit",
    "test": "vitest run",
    "test:coverage": "vitest run --coverage",
    "test:watch": "vitest run --watch"
  },
  "dependencies": {
    "next": "15.2.3",
    "react": "18.3.1",
    "react-dom": "18.3.1"
  },
  "devDependencies": {
    ...
    "@types/react": "^18.3.1",
    "@types/react-dom": "^18.3.1",
    ...
    "vitest": "^3.0.9",
     "@testing-library/dom": "^10.4.0",
    "@testing-library/jest-dom": "^6.6.3",
    "@testing-library/react": "^16.2.0",
    "@testing-library/react-native": "^13.2.0",
    "@types/react-dom": "^19.0.4",
    "@vitejs/plugin-react": "^4.3.4",
  }
}

[MatanBobi]

Can you please share a minimal reproduction for us to help?