unit test raises error because of .getContext() is not implemented

I am writing tests using Jest for components that use canvas elements. I keep getting an error when I run my tests that looks like this.

Error: Not implemented: HTMLCanvasElement.prototype.getContext (without installing the canvas npm package)

From my understanding Jest uses jsdom for its testing and that jsdom is compatible with canvas if you install the canvas or canvas-prebuilt packages.

I have tried installing each of these packages and neither of them have resolved the error. The only thing that I think could be going wrong is that jsdom cannot find the canvas or canvas-prebuilt packages. Does anyone know a way to fix this error or test to see if jsdom is finding the other packages? Thanks a lot!

My team is using create-react-app and we had previously addressed this problem by adding the npm package jest-canvas-mock. Now after upgrading to react-scripts 3.4.1, we also had to add a specific import to our src/setupTests.ts file:

import 'jest-canvas-mock';

You can create your own mock of the function in a jest setup script

HTMLCanvasElement.prototype.getContext = () => { 
  // return whatever getContext has to return
};

I had similar problem with my Jest tests, and solved it by installing jest-canvas-mock.

Both answers above work. However, just wanted to add that in case of create-react-app, it doesn't support the 'setupFiles' required by jest conf in package.json for jest-canvas-mock.

I got around this by adding the import statement in each of the test files that were invoking the canvas element(in my case 3). Then, I moved the import statement to the setupTests.js file and removed that requirement as well.

I've solved it by installing jest-canvas-mock

npm i --save-dev jest-canvas-mock

And adding this configuration on package.json

{
  "jest": {
    "setupFiles": [
      "jest-canvas-mock"
    ],
  }
}

I experienced the same problem using react-scripts 3.0.1 and solved it by installing jest-canvas-mock as a dev dependency and importing it (import 'jest-canvas-mock') on my app.test.js file (where I got that error from) only as importing it on setupTests.js would unnecessarily import the package in every single test file.