jest-electron

jest use JSDOM instead of a browser

As a result, it can't handle canvas or storage.

Canvas [object HTMLCanvasElement] is unable to provide a 2D context.

That's where electron comes in.

package.json

code:diff

+ "runner": "jest-electron/runner",

+ "testEnvironment": "jest-electron/environment",

- "testEnvironment": "jest-environment-jsdom-fourteen"

Now we can run tests involving canvas.

$ DEBUG_MODE=1 npm test

to display the browser and run the test.

Which means you'd expect the app screen to come up, but it doesn't...

I wonder how we'll see that screen when the test fails...

$ npm test

I couldn't see the console.log output even with various options when I did the following, but maybe it is supposed to be viewed on electron

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$ npm install --save jest-electron

need eject before config

Out of the box, Create React App only supports overriding these Jest options:

These options in your package.json Jest configuration are not currently supported by Create React App:

• verbose

• runner

• testEnvironment

If you wish to override other Jest options, you need to eject from the default setup. You can do so by running npm run eject but remember that this is a one-way operation. You may also file an issue with Create React App to discuss supporting more options out of the box.

$ npx create-react-app --typescript test-jest-electron

$ cd test-jest-electron/

$ npm run eject

config

package.json

code:diff

+ "runner": "jest-electron/runner",

+ "testEnvironment": "jest-electron/environment",

- "testEnvironment": "jest-environment-jsdom-fourteen"

code::

console.error node_modules/jest-environment-jsdom-fourteen/node_modules/jsdom/lib/jsdom/virtual-console.js:29

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

Keep the electron browser window for debugging, set process env DEBUG_MODE=1.

DEBUG_MODE=1 jest

$ DEBUG_MODE=1 npm test

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