Enzyme Framework Interview Questions and Answers

Learn and master the top 30 Enzyme framework interview questions along with detailed answers with code snippets.

1. What is Enzyme?
   Enzyme is a JavaScript testing utility for React developed by Airbnb.
   
   It provides a set of APIs to manipulate and traverse React components’ output and make assertions on their behavior.
   
2. How do you install Enzyme?
   You can install Enzyme using npm by running the following command:

npm install enzyme enzyme-adapter-react-16 --save-dev

3. How do you configure Enzyme with a specific version of React?
   You need to configure Enzyme to work with the specific version of React you’re using.
   
   You can do this by creating a setupTests.js file in your project’s src directory with the following contents:

import Enzyme from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

Enzyme.configure({ adapter: new Adapter() });

4. How do you render a React component using Enzyme?
   You can use the shallow method from Enzyme to render a React component.
   
   Here’s an example:

import { shallow } from 'enzyme';
import MyComponent from './MyComponent';

test('renders MyComponent', () => {
  const wrapper = shallow(<MyComponent />);
  expect(wrapper.exists()).toBe(true);
});

5. What is the difference between shallow, mount, and render in Enzyme?

• shallow: Shallow rendering renders only the current component, not its children. It’s useful for isolating the component under test.
• mount: Full rendering renders the current component and its children, including all lifecycle methods. It’s useful for testing the component’s interactions with child components and the DOM.
• render: Static rendering renders the current component and its children to static HTML. It’s useful for snapshot testing and generating HTML for server-side rendering.

6. How do you find elements using Enzyme’s selectors?
Enzyme provides various selectors to find elements within a rendered component.

Some examples include find, filter, contains, hasClass, and more.

Here’s an example using find:

const wrapper = shallow(<MyComponent />);
const element = wrapper.find('.my-class');

7. How do you simulate events using Enzyme?
   You can use the simulate method to simulate events on elements in Enzyme. Here’s an example:

const wrapper = shallow(<Button onClick={handleClick} />);
wrapper.find('button').simulate('click');
expect(handleClick).toHaveBeenCalled();

8. How do you test the state of a component using Enzyme?
   You can access and test the state of a component using the state method from Enzyme.
   
   Here’s an example:

const wrapper = shallow(<MyComponent />);
expect(wrapper.state('count')).toBe(0);

9. How do you test the props of a component using Enzyme?
   You can access and test the props of a component using the props method from Enzyme.
   
   Here’s an example:

const wrapper = shallow(<MyComponent name="John" />);
expect(wrapper.props().name).toBe('John');

10. How do you test the lifecycle methods of a component using Enzyme?
    You can use the Enzyme methods like componentDidMount, componentDidUpdate, and componentWillUnmount to test lifecycle methods.
    
    Here’s an example:

const componentDidMountSpy = jest.spyOn(MyComponent.prototype, 'componentDidMount');
const wrapper = mount(<MyComponent />);
expect(componentDidMountSpy

).toHaveBeenCalled();
componentDidMountSpy.mockRestore();

11. How do you test Redux-connected components with Enzyme?
    To test Redux-connected components, you can use the Provider component from react-redux and wrap your component in it.
    
    Here’s an example:

import { Provider } from 'react-redux';
import configureStore from 'redux-mock-store';

const mockStore = configureStore([]);
const store = mockStore({});

const wrapper = mount(
  <Provider store={store}>
    <ConnectedComponent />
  </Provider>
);

12. How do you test components that use React Router with Enzyme?
    You can use the MemoryRouter component from react-router-dom to wrap your components during testing.
    
    Here’s an example:

import { MemoryRouter } from 'react-router-dom';

const wrapper = mount(
  <MemoryRouter initialEntries={['/']} initialIndex={0}>
    <MyComponent />
  </MemoryRouter>
);

13. How do you test components that use context with Enzyme?
    You can use the React.createContext function and the Provider component to provide context values for testing.
    
    Here’s an example:

const MyContext = React.createContext();

const wrapper = mount(
  <MyContext.Provider value={contextValue}>
    <MyComponent />
  </MyContext.Provider>
);

14. How do you test components that use hooks with Enzyme?
    Enzyme’s mount method supports testing components that use hooks. Simply render the component using mount as usual.
    
    Here’s an example:

const wrapper = mount(<MyComponent />);

15. How do you test components that make API calls using Enzyme?
    You can use the jest.mock function to mock API calls in Enzyme tests.
    
    Here’s an example:

import axios from 'axios';

jest.mock('axios');

test('component with API call', async () => {
  axios.get.mockResolvedValue({ data: 'mocked data' });

  const wrapper = mount(<MyComponent />);
  await wrapper.instance().fetchData();

  expect(wrapper.state('data')).toEqual('mocked data');
});

16. How do you test components with asynchronous behavior using Enzyme?
    You can use async/await or promises along with the update method from Enzyme to test components with asynchronous behavior.
    
    Here’s an example:

test('component with async behavior', async () => {
  const wrapper = mount(<MyComponent />);
  await Promise.resolve(); // Let the promises resolve
  wrapper.update();
  // Perform assertions on the updated component
});

17. How do you test components with Redux-saga using Enzyme?
    You can use the redux-saga-test-plan library to test components with Redux-saga.
    
    It provides a testing DSL specifically designed for testing sagas.
    
18. How do you test components with GraphQL using Enzyme?
    You can mock the GraphQL client or use a library like apollo-boost to provide a mocked client for testing components with GraphQL.
    
    Here’s an example:

import { ApolloProvider } from '@apollo/client';
import { MockedProvider } from '@apollo/client/testing';
import { GET_USERS_QUERY } from './queries';

const mocks = [
  {
    request: {
      query: GET_USERS_QUERY,
    },
    result: {
      data: {
        users: ['John', 'Jane'],
      },
    },
  },
];

const wrapper = mount(
  <ApolloProvider client={mockedClient}>
    <MockedProvider mocks={mocks} addTypename={false}>
      <MyComponent />


 </MockedProvider>
  </ApolloProvider>
);

19. How do you test components with authentication using Enzyme?
    You can provide a mock authentication context or use a library like react-mock-auth to simulate authentication for testing components with authentication.
    
20. How do you test components with internationalization (i18n) using Enzyme?
    You can provide a mock i18n context or use a library like react-intl to simulate internationalization for testing components with i18n.
    
21. How do you test components with animations using Enzyme?
    You can use the requestAnimationFrame API or mock it using a library like raf to test components with animations.
    
    Here’s an example:

import raf from 'raf';

test('component with animations', () => {
  raf.polyfill();

  const wrapper = mount(<MyComponent />);
  // Perform assertions on the animated component
});

22. How do you test components that use portals using Enzyme?
    Enzyme supports testing components that use portals.
    
    Simply render the component as usual, and the portal content will be included in the component’s output.
    
23. How do you test components that use React.lazy and Suspense using Enzyme?
    Enzyme doesn’t natively support testing components that use React.lazy and Suspense.
    
    However, you can use libraries like enzyme-async-helpers to handle the loading state and test the component once it’s loaded.
    
24. How do you test components with CSS modules using Enzyme?
    Enzyme doesn’t directly interact with CSS modules.
    
    You can test components with CSS modules by asserting on the rendered component’s HTML structure and classes.
    
25. How do you test components that use Redux-thunk using Enzyme?
    You can mock Redux actions and use the redux-mock-store library to test components that use Redux-thunk.
    
    Here’s an example:

import configureMockStore from 'redux-mock-store';
import thunk from 'redux-thunk';
import { fetchUsers } from './actions';

const mockStore = configureMockStore([thunk]);

test('component with Redux-thunk', async () => {
  const store = mockStore({ users: [] });
  await store.dispatch(fetchUsers());
  const actions = store.getActions();
  // Perform assertions on the dispatched actions and store state
});

26. How do you test components with WebSocket functionality using Enzyme?
    To test components with WebSocket functionality, you can mock the WebSocket object and simulate WebSocket events using Jest’s jest.spyOn or by manually triggering event callbacks.
    
27. How do you test components that use drag and drop functionality using Enzyme?
    You can use libraries like react-dnd-test-utils or react-beautiful-dnd-test-utils to simulate drag and drop behavior and test components with drag and drop functionality.
    
28. How do you generate code coverage reports for Enzyme tests?
    You can generate code coverage reports for Enzyme tests by using Jest’s built-in code coverage functionality.
    
    Running npm test -- --coverage will generate a coverage report in the coverage directory.
    
29. How do you mock external dependencies in Enzyme tests?
    You can use Jest’s jest.mock function to mock external dependencies and provide custom implementations.
    
    This allows you to isolate the component under test.
    
30. How do you configure Enzyme with custom settings?
    You can configure Enzyme with custom settings by using the enzyme.configure method.
    
    For example, you can configure Enzyme to use a different adapter or enable features like React 17’s new rendering behavior.