How can one stub ffmpeg

[gmbwa]

How can one stub ffmpeg while testing the function below.

I wanted to test out the a few different scenarios eg.
error,
.on('end'
calling .on('progress' a few times

function resizeMe(url){
      ffmpeg(url)
      .on('end', async (e) => {})
      .on('error', (error) => {})
      .on('progress', (progress) => {})
      .size(size)
      .output(`${filePath}`)
      .run();
}

(note: if the problem only happens with some inputs, include a link to such an input file)

Expected results

Observed results

Checklist

• I have read the FAQ
• I tried the same with command line ffmpeg and it works correctly (hint: if the problem also happens this way, this is an ffmpeg problem and you're not reporting it to the right place)
• I have included full stderr/stdout output from ffmpeg