javascript - How to see what the rendered React component looks like in the Jest unit test? - Stack Overflow

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I'm trying to run a test for the React ponent. I need to check how it looks like after rendering. Tried to use ReactDOMServer.renderToString() but it fails. Here is the code:

import { NewRec } from '../src/ponents/edit';
import { shallow } from 'enzyme';
import React from 'react/lib/ReactWithAddons';
import ReactDOMServer from 'react-dom/server';

jest.mock('react-dom');
jest.mock('react/lib/ReactDefaultInjection');

describe('NewRec ponent', () => {
    const ponent = shallow(<NewRec />);
    it('returns true if blah blah', ()=>{
        var htmlstring = ReactDOMServer.renderToString(<ponent />);
    });
});

I'm getting the following error:

Invariant Violation: There is no registered ponent for the tag ponent

I tried to call it like: var htmlstring = ReactDOMServer.renderToString(ponent); then I get this error:

Invariant Violation: renderToString(): You must pass a valid ReactElement.

Does anyone knows where the problem is?

I'm trying to run a test for the React ponent. I need to check how it looks like after rendering. Tried to use ReactDOMServer.renderToString() but it fails. Here is the code:

import { NewRec } from '../src/ponents/edit';
import { shallow } from 'enzyme';
import React from 'react/lib/ReactWithAddons';
import ReactDOMServer from 'react-dom/server';

jest.mock('react-dom');
jest.mock('react/lib/ReactDefaultInjection');

describe('NewRec ponent', () => {
    const ponent = shallow(<NewRec />);
    it('returns true if blah blah', ()=>{
        var htmlstring = ReactDOMServer.renderToString(<ponent />);
    });
});

I'm getting the following error:

Invariant Violation: There is no registered ponent for the tag ponent

I tried to call it like: var htmlstring = ReactDOMServer.renderToString(ponent); then I get this error:

Invariant Violation: renderToString(): You must pass a valid ReactElement.

Does anyone knows where the problem is?

• javascript
• unit-testing
• reactjs
• jestjs

Share Improve this question Follow edited Nov 9, 2016 at 22:09 Andreas Köberle 111k5858 gold badges280280 silver badges307307 bronze badges asked Nov 9, 2016 at 10:01 BirishBirish 5,83277 gold badges3636 silver badges5656 bronze badges

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2 Answers 2

Sorted by: Reset to default 2

There is the snapshot feature in Jest where it stores the rendered tree as a file. Note that you have to install enzyme-to-json as well to convert the enzyme rendered ponent to something the snapshot method can understand.

import { NewRec } from '../src/ponents/edit';
import { shallow } from 'enzyme';
import { shallowToJson } from 'enzyme-to-json';

describe('NewRec ponent', () = > {
  it('returns true if blah blah', () = > {
    const ponent = shallow(<NewRec />);
    expect(shallowToJson(ponent)).toMatchSnapshot();
  });
});

This will create a new file in __snapshot__ folder in your test folder, where you can inspect the rendered result. Every time you rerun the test, the ponent will be tested against the snapshot.

If you don't use enzyme, you can use Facebook's react-test-renderer too, it's even simpler:

import React from "react";
import renderer from "react-test-renderer";

test("Test 1", () => {
  const ponent = renderer.create(
    <TestItem />
  );

  let tree = ponent.toJSON();
  expect(tree).toMatchSnapshot();
});

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