How to test handler with jest?

user_5729613 0
Viewed 1245

I'm trying to mock an event handler from the arcgis js library using jest, but am having trouble getting a reference to the handler and triggering the callback function. I decided to mock the event handler using node's built-in events module but when I emit the event, the callback is never entered.

foo.ts

  createSomething(
    onComplete: fooCompleteCallback
  ): void {
    if (this.isReady()) {
      const handler = foo.addEventHandler((event) => {
        if (event.state === EVENT_COMPLETE) {
          handler.remove();
          onComplete(event.graphic);
        }
      });
      foo.create();
    }
  }

foo.test.ts

import events from 'events';

class foo {
  eventEmitter = new events.EventEmitter();
  
  addEventHandler = () => this.eventEmitter.on('complete', (callback) => callback({state: 'complete'}));
  isReady = jest.fn().mockImplementation(() => true);
  create = () => this.eventEmitter.emit('complete');
}
export default new foo();
jestjs handler events
1 Answers

I was pretty close, here is what the correct test code looks like

foo.test.ts

class foo {

  eventEmitter = new events.EventEmitter();
  handler = {remove: jest.fn()}

  fooEvent= {
    state: 'complete'
  }
  
  addEventHandler = (callback) => {
    this.eventEmitter.on('complete', () => callback(this.sketchEvent)); 
    return this.handler;
  };

  create = (createOptions) => {this.eventEmitter.emit('complete')};
}
export default new foo();
user_57296130
Related