¿Cómo puedo burlarme del argumento del evento en karma chai sinon mocha?

 it('should have onmute event on tracks', async () => { if (fakeAudioTracks[0].onmute !== null) { console.log('before fakeAudioTracks[0] ', fakeAudioTracks[0]); eventCallbackSpy = Sinon.spy(); subscriptions.events['track:mute'].set(subscription.listener.id, eventCallbackSpy); fakeAudioTracks[0].enabled = true; fakeAudioTracks[0].onmute(new Event('mute')); Sinon.assert.called(eventCallbackSpy); // expect(eventCallbackSpy.getCall(0).args[0].action).to.be.equal('muted'); console.log('After fakeAudioTracks[0] ', fakeAudioTracks[0]); expect(eventCallbackSpy.getCall(0).args[0].action).to.be.equal('muted'); } });

Este es mi caso de prueba, quiero pasar un argumento fakeAudioTracks[0] a fakeAudioTracks[0].onmute(new Event('mute')); este.

Mi onmute -

 export function onmute(event: Event) : void { console.log('event ', event.target); const onmuteListeners: eventListeners = subscriptions.events['track:mute']; for (const entry of onmuteListeners) { const listener = entry[1]; if (listener) { listener({ action: 'muted' || 'unmuted', // need to check the event.target and return this. // action: event.target.enabled === 'true' ? 'muted' : 'unmuted', track: <MediaStreamTrack> event.target, }); } } }