function evaluator (_selector) {
    return document.querySelectorAll(_selector).length
  }
A custom Nightwatch assertion. The assertion name is the filename.

Example usage:
  browser.assert.elementCount(selector, count)

For more information on custom assertions see:
  https://nightwatchjs.org/guide/extending-nightwatch/#writing-custom-assertions


@param {string|object} selectorOrObject
@param {number} count