old_contents: /**
   * Checks if the given element is visible on the page.
   *
   * ```
   * this.demoTest = function (browser) {
   *   browser.assert.visible('.should_be_visible');
   *   browser.assert.visible({selector: '.should_be_visible'});
   *   browser.assert.visible({selector: '.should_be_visible', suppressNotFoundErrors: true});
   * };
   * ```
   *
   * @method visible
   * @param {string|object} definition The selector (CSS / Xpath) used to locate the element. Can either be a string or an object which specifies [element properties](https://nightwatchjs.org/guide#element-properties).
   * @param {string} [msg] Optional log message to display in the output. If missing, one is displayed by default.
   * @api assertions
   */
  exports.assertion = function(definition, msg) {
    this.options = {
      elementSelector: true
    };
  
    this.formatMessage = function() {
      const message = msg || `Testing if element %s ${this.negate ? 'is not visible' : 'is visible'}`;
  
      return {
        message,
        args: [this.elementSelector]
      }
    };
  
    this.expected = function() {
      return this.negate ? 'is not visible' : 'is visible';
    };
  
    this.evaluate = function(value) {
      return value === true;
    };
  
    this.actual = function(passed) {
      return passed ? 'visible' : 'not visible';
    };
  
    this.command = function(callback) {
      this.api.isVisible(definition, callback);
    };
  };
  
new_contents: /**
   * Checks if the given element is visible on the page.
   *
   * ```
   * this.demoTest = function (browser) {
   *   browser.assert.visible('.should_be_visible');
   *   browser.assert.visible({selector: '.should_be_visible'});
   *   browser.assert.visible({selector: '.should_be_visible', suppressNotFoundErrors: true});
   * };
   * ```
   *
   * @method visible
   * @param {string|object} definition The selector (CSS / Xpath) used to locate the element. Can either be a string or an object which specifies [element properties](https://nightwatchjs.org/guide/working-with-page-objects/#element-properties).
   * @param {string} [msg] Optional log message to display in the output. If missing, one is displayed by default.
   * @api assertions
   */
  exports.assertion = function(definition, msg) {
    this.options = {
      elementSelector: true
    };
  
    this.formatMessage = function() {
      const message = msg || `Testing if element %s ${this.negate ? 'is not visible' : 'is visible'}`;
  
      return {
        message,
        args: [this.elementSelector]
      }
    };
  
    this.expected = function() {
      return this.negate ? 'is not visible' : 'is visible';
    };
  
    this.evaluate = function(value) {
      return value === true;
    };
  
    this.actual = function(passed) {
      return passed ? 'visible' : 'not visible';
    };
  
    this.command = function(callback) {
      this.api.isVisible(definition, callback);
    };
  };
  
subject: Update visible.js (#2393)