React testing library: Test styles (specifically background image)

Asked 2/11, 2018 at 13:4 Answered 26/2 at 10:6

Solved reactjs typescript unit-testing jestjs react-testing-library

I'm building a React app with TypeScript. I do my component tests with react-testing-library.

I'm buildilng a parallax component for my landing page.

The component is passed the image via props and sets it via JSS as a background image:

<div
  className={parallaxClasses}
  style={{
    backgroundImage: "url(" + image + ")",
    ...this.state
  }}
>
  {children}
</div>

Here is the unit test that I wrote:

import React from "react";
import { cleanup, render } from "react-testing-library";
import Parallax, { OwnProps } from "./Parallax";
afterEach(cleanup);

const createTestProps = (props?: object): OwnProps => ({
  children: null,
  filter: "primary",
  image: require("../../assets/images/bridge.jpg"),
  ...props
});

describe("Parallax", () => {
  const props = createTestProps();
  const { getByText } = render(<Parallax {...props} />);
  describe("rendering", () => {
    test("it renders the image", () => {
      expect(getByText(props.image)).toBeDefined();
    });
  });
});

But it fails saying:

● Parallax › rendering › it renders the image

    Unable to find an element with the text: bridge.jpg. This could be because the text is broken up by multiple elements. In this case, you can provide a function for your text matcher to make your matcher more flexible.

    <body>
      <div>
        <div
          class="Parallax-parallax-3 Parallax-primaryColor-4"
          style="background-image: url(bridge.jpg); transform: translate3d(0,0px,0);"
        />
      </div>
    </body>

      16 |   describe("rendering", () => {
      17 |     test("it renders the image", () => {
    > 18 |       expect(getByText(props.image)).toBeDefined();
         |              ^
      19 |     });
      20 |   });
      21 | });

      at getElementError (node_modules/dom-testing-library/dist/query-helpers.js:30:10)
      at getAllByText (node_modules/dom-testing-library/dist/queries.js:336:45)
      at firstResultOrNull (node_modules/dom-testing-library/dist/query-helpers.js:38:30)
      at getByText (node_modules/dom-testing-library/dist/queries.js:346:42)
      at Object.getByText (src/components/Parallax/Parallax.test.tsx:18:14)

How can I test that the image is being set as a background image correctly with Jest and react-testing-library?

Silvanus answered 2/11, 2018 at 13:4 Comment(0)

getByText won't find the image or its CSS. What it does is to look for a DOM node with the text you specified.

In your case, I would add a data-testid parameter to your background (<div data-testid="background">) and find the component using getByTestId.

After that you can test like this:

expect(getByTestId('background')).toHaveStyle(`background-image: url(${props.image})`)

Make sure you install @testing-library/jest-dom in order to have toHaveStyle.

Bacchius answered 2/11, 2018 at 13:21 Comment(6)

This is not working for me, I get TypeError: expect(...).toHaveValue is not a function even with jest-dom installed. Could it be because I'm testing a styled-component? – Benedicite 13/1, 2020 at 22:45

Got it, had to add import '@testing-library/jest-dom/extend-expect' to the test file. Found it here spectrum.chat/testingjavascript/help/… – Benedicite 13/1, 2020 at 22:54

I really suggest you will make a setupTests file which import this to any jest file you use :) and than all of the "toHaveStyle, Content, etc...." will auto import. at any test file. keep the development faster and solve issues you may have when you forgot to import it. – Photomicroscope 16/8, 2020 at 14:9

@LuizHenriqueGuerra your error msg says: toHaveValue The answer says toHaveStyle – Amye 20/10, 2020 at 13:40

@Amye either way none of the methods from the expect api were working without the import in my next comment – Benedicite 27/11, 2020 at 1:50

Install @testing-library/jest-dom, not jest-dom – Anchor 1/9, 2022 at 3:15

If you want to avoid adding data-testid to your component, you can use container from react-testing-library.

const {container} = render(<Parallax {...props})/>
expect(container.firstChild).toHaveStyle(`background-image: url(${props.image})`)

This solution makes sense for your component test, since you are testing the background-image of the root node. However, keep in mind this note from the docs:

If you find yourself using container to query for rendered elements then you should reconsider! The other queries are designed to be more resiliant to changes that will be made to the component you're testing. Avoid using container to query for elements!

Nape answered 19/6, 2019 at 18:50 Comment(1)

One way to avoid the problem of making the implementation-detail assumption that it's the container's first child that carries the background image might be to give the element with the background image an aria-role of an image (role="img") and then use getByRole('img') instead of container.firstChild. Then the tester looks up the tree for the first element that acts as an image. – Schubert 2/1, 2020 at 11:12

in addition to toHaveStyle JsDOM Matcher, you can use also style property which is available to the current dom element

Element DOM API

expect(getByTestId('background').style.backgroundImage).toEqual(`url(${props.image})`)

also, you can use another jestDOM matcher

toHaveAttribute Matcher

expect(getByTestId('background')).toHaveAttribute('style',`background-image: url(${props.image})`)

Emlen answered 7/5, 2022 at 0:36 Comment(0)

Simple solution for testing Component css with react-testing-library. this is helpful for me it is working perfect.

test('Should attach background color if user
      provide color from props', () => {
render(<ProfilePic name="Any Name" color="red" data- 
 testid="profile"/>);
//or can fetch the specific element from the component 
const profile = screen.getByTestId('profile');

const profilePicElem = document.getElementsByClassName(
  profile.className,
);
const style = window.getComputedStyle(profilePicElem[0]);

//Assertion 
expect(style.backgroundColor).toBe('red');
});

Cetacean answered 23/6, 2021 at 5:38 Comment(0)

I'm encountering an issue with backgroundImage in my Vite React TypeScript Jest project. When I create a project using create-react-app, everything works as expected. However, when I use Vite, the following code:

getByTestId('background').style.backgroundImage

returns url(default), instead of the expected value.

I suspect I might be missing some configuration. Is there anyone here who can assist me in resolving this issue? I'm using Vite with React, TypeScript, and Jest.

Perfection answered 26/2 at 10:6 Comment(1)

@Emlen please look into this – Perfection 26/2 at 10:12

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