Property `*` does not exist in the provided object

Question

I have a class

export class Player {
  constructor() {}
  play = async (soundUrl: any) => {
    const { sound } = await Audio.Sound.createAsync(soundUrl);
    await sound.playAsync();
  };
  faillure = () => {
    this.play(testFailedSound);
  };

  success = () => {
    this.play(successSound);
  };
  exerciceSuccess = () => {
    this.play(exerciceSuccess);
  };
}

When I try to mock the success method with a spyOn

const successSoundSpy = jest.spyOn(Player.prototype, "success");

I got the error message Property 'success' does not exist in the provided object

Answer 1

I spent at least 3 hours trying to figure out why my code wasn’t working, and it turns out the issue was with how I defined the success function. I initially used an arrow function:

success = () => {
    this.play(successSound);
  };

But this approach didn’t bind this to the class instance correctly, causing issues when trying to call class methods.

The fix was to change the function to a standard method:

success(){
    this.play(successSound);
  };

This correctly binds this to the class instance, solving the problem.