How to mock a worker when testing with jest? Should we even test workers?

[manjula-dube]

ReferenceError: Worker is not defined

[manjula-dube]

Reference: jestjs/jest#3449

[nitish24p]

wondering if setting a mock worker class would work

  class Worker {
    constructor(stringUrl) {
      this.url = stringUrl;
      this.onmessage = () => {};
    }

    postMessage(msg) {
      this.onmessage(msg);
    }
  }

and then doing

window.Worker = Worker

[manjula-dube]

I tried but it doesn't work I am wondering should we even test external resources ?

[prateekbh]

did you guys get to close this?
i am kinda stuck on the same thing

[hayait599]

Same issue :(

[nitish24p]

Havent had time to see this but maybe this would help ? https://www.npmjs.com/package/jsdom-worker

[andreasjhagen]

Havent had time to see this but maybe this would help ? https://www.npmjs.com/package/jsdom-worker

Thanks, the package actually works. It produces some error message though, even when all tests pass. It doesn't look like it's maintained any longer unfortunately

[andreasjhagen]

For people like me, that want to keep the console clean and want to get rid of the error message after successfull tests, I created a fork and fixed it:

https://www.npmjs.com/package/jsdom-worker-fix

[ghost]

For people like me, that want to keep the console clean and want to get rid of the error message after successfull tests, I created a fork and fixed it:

https://www.npmjs.com/package/jsdom-worker-fix

@andreasjhagen can u show implementation in create-react-app, if possible

[ViniciusResende]

If your working with Shared Workers this is what has worked for me.
First, you create a mock folder like this :

├── src
│     ├── workers
│        ├── __mocks__
│        │   └── myworker.worker.js
│        └── myworker.worker.js

And then you can add a mock for your worker like this:

class SharedWorker {
  constructor(stringUrl) {
    this.url = stringUrl;
    this.onconnect = () => {};
    this.port = {
      start: () => {},
      postMessage: () => {},
      onmessage: () => {},
    };
  }
}

export default SharedWorker;

finally, in your tests that require your worker, you can do this:

jest.mock('./path-to-your-worker')