mocha-failure-snapshot.js

const sanitize = require('sanitize-filename');

// Declared outside any describe() or context() block so that it's called after every test.

// this is bound by Mocha to let us have access to the current test state, so we make sure
// to avoid a fat-arrow function declaration here.
afterEach(function(){
  const filename = `${sanitize(this.currentTest.title.replace(/\s+/g, '-'))}-${+new Date()}`;

  if (this.currentTest.state === 'failed') {
    return captureLogs(`${filename}.log`)
    .then(() => takeScreenshot(`${filename}.png`));
  }
});