React 19 - Objects are not valid as a React child

• @testing-library/react version: 16.3.0
• Testing Framework and version: vitest 3.2.4
• DOM Environment: jsdom 26.1.0

Relevant code or config:

//package.json
{
  "name": "@emg-hub/ui",
  "version": "0.0.0",
  "private": true,
  "exports": {
    "./*": "./src/*.tsx"
  },
  "scripts": {
    "lint": "eslint . --max-warnings 0",
    "generate:component": "turbo gen react-component",
    "test": "vitest"
  },
  "devDependencies": {
    "@emg-hub/eslint-config": "*",
    "@emg-hub/typescript-config": "*",
    "@testing-library/dom": "^10.4.1",
    "@testing-library/jest-dom": "^6.8.0",
    "@testing-library/react": "^16.3.0",
    "@testing-library/user-event": "^14.6.1",
    "@types/node": "^24.3.0",
    "@types/react": "19.1.12",
    "@types/react-dom": "19.1.9",
    "@vitejs/plugin-react": "^5.0.2",
    "@vitest/coverage-v8": "^3.2.4",
    "@vitest/ui": "^3.2.4",
    "eslint": "^9.34.0",
    "jsdom": "^26.1.0",
    "typescript": "5.9.2",
    "vite-tsconfig-paths": "^5.1.4",
    "vitest": "^3.2.4"
  },
  "dependencies": {
    "react": "^19.1.1",
    "react-dom": "^19.1.1"
  }
}

//vitest.config.mjs
import { defineConfig } from 'vite'
import react from '@vitejs/plugin-react'
import { configDefaults } from 'vitest/config'

export default defineConfig({
  plugins: [react()],
  test: {
    globals: true,
    environment: 'jsdom',
    exclude: [...configDefaults.exclude, 'e2e/*'], // optional
    coverage: {
      provider: 'v8', // or 'c8'
      reporter: ['text', 'json', 'html'],
      exclude: ['vite.config.*', 'src/main.*', '**/*.d.ts', '**/__tests__/**'],
    },
  },
})

//button.tsx
import { ReactNode } from "react";

interface ButtonProps {
  children: ReactNode;
  className?: string;
  appName: string;
}

export const Button = ({ children, className, appName }: ButtonProps) => {
  return (
    <button
      className={className}
      onClick={() => alert(`Hello from your ${appName} app!`)}
    >
      {children}
    </button>
  );
};

//button.test.tsx
import { render, screen, fireEvent } from '@testing-library/react';
import userEvent from '@testing-library/user-event';
import { describe, it, expect, beforeEach, vi } from 'vitest';
import { Button } from './button';

describe('Button', () => {
  beforeEach(() => {
    vi.clearAllMocks();
  });

  describe('rendering', () => {
    it('renders simple div', () => {
      render(<div>Click me</div>);
      expect(screen.getByText('Click me')).toBeInTheDocument();
    });
    it('renders with children text', () => {
      render(<Button appName="test">Click me</Button>);
      expect(screen.getByRole('button', { name: 'Click me' })).toBeInTheDocument();
    });
 });
});

What you did:

Tried running simple test using npm run test

What happened:

I got the 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." even on the simple test 'renders simple div'

Problem description:

I can't seem to run any test on this React component, with React 19. I also tried using Jest but same issues. I followed a guide to setup my test config. It's a simple internal package in a turborepo arch. The issue is always on the render method of the @testing-library/react

Suggested solution

I don't have any. I saw a similar issue #1387 but it was for a NextJs project and the solution offered isn't possible for me.

Start with package.json and vitest.config.mjs, then run npm run test against button.test.tsx to reproduce the render failure. Check how the React, React DOM, Vite, and @testing-library/react versions are resolved in this package. Done means both the simple div test and the Button rendering test pass.