运行React组件测试用例时出现TypeError: Cannot read property 'prototype' of undefined错误如何解决？

I’ve run into this exact error multiple times when working with Enzyme and React tests—let’s break down the fixes step by step:

The Root Cause #

This error almost always stems from a missing or mismatched Enzyme adapter for your React version. Enzyme requires an adapter tailored to your React version to interact with React’s internal APIs correctly; without it, you’ll get this "prototype undefined" crash.

Step 1: Install the Correct Enzyme Adapter #

First, install the adapter that matches your React version:

• For React 16:
  npm install enzyme-adapter-react-16 --save-dev
• For React 17 (official Enzyme doesn’t support 17 natively):
  npm install @wojtekmaj/enzyme-adapter-react-17 --save-dev
• For React 18:
  npm install @wojtekmaj/enzyme-adapter-react-18 --save-dev

Step 2: Configure the Adapter in Your Test #

Add the adapter configuration at the top of your test file (or a global setup file like setupTests.js if you want it applied to all tests):

import React from 'react';
import { render } from 'enzyme';
import Enzyme from 'enzyme';
// Import the adapter you installed
import Adapter from 'enzyme-adapter-react-16'; 

// Configure Enzyme with the adapter
Enzyme.configure({ adapter: new Adapter() });

import FileUpload from '../Components/Elements/fileUpload';

Step 3: Fix Test Structure #

In your current code, you’re rendering the component outside the it block (directly in the describe block). This runs before Enzyme is fully configured, which can also trigger the error. Move the render call inside your test case:

describe('FileUpload component', ()=>{
  it('Test init status', function() {
    // Render the component inside the test block
    const wrapper = render(<FileUpload />); 
    expect(wrapper.find('input').length).toBe(2);
    expect(wrapper.find('input').text()).toEqual('');
  });
});

Bonus: Verify Package Compatibility #

Double-check that your enzyme, react, and react-dom versions are compatible. For example:

• Enzyme 3.x works with React 16.x
• Enzyme 3.x + the community adapters work with React 17/18

After making these changes, your test should run without the prototype error.

内容的提问来源于stack exchange，提问作者Ravi Kumar Gopalakrishnan