CODEWITHSUNDEEP
node.jstypescriptunit-testingjestjs
JesterXIII
JesterXIII

Reputation: 139

How can I emit error event in jest and typescript

For example, I'm using Archiver:

archive.on('error', err => {
  if (typeof callback === 'function') {
    callback.call(this, err);
  } else {
    throw err;
  }
});

These lines are uncovered according to jest. How can you emit this error? A mock?

Upvotes: 1

Views: 1111

Answers (1)

Krzysztof Atłasik
Krzysztof Atłasik

Reputation: 22595

You can move your callbacks to other module and then export it, like:

//calbacks.js

const errorCallback = callback => err => {
  if (typeof callback === 'function') {
    callback.call(this, err);
  } else {
    throw err;
  }
}

export {errorCallback} // es6 named export

Then you can import it in your main file:

import { errorCallback } from "./callbacks.js" //path should be correct, this would work if you have both files in same directory

...

archive.on('error', errorCallback(callback)) //pass callback to curried function

You can also just import it in spec and test it:

const spy = jest.fn()

errorCallback(fn)("error")    
expect(spy).toBeCalledWith("error");

and also test case when callback is not function:

expect(() => {
    errorCallback("notFunction")("error")
}).toThrow()

Upvotes: 1

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