code: function copyAttributesToBodyCopy(bodyCopy, testingContainer) {
    let attributesToCopy = testingContainer.prop('attributes');
    percyJQuery.each(attributesToCopy, function() {
      // Special case for the class attribute - append new classes onto existing body classes
      if (this.name === 'class') {
        bodyCopy.attr(this.name, bodyCopy.attr('class') + ' ' + this.value);
      } else {
        bodyCopy.attr(this.name, this.value);
      }
    });
  }
docs: Copy attributes from Ember's rootElement to the DOM snapshot <body> tag. Some applications rely on setting attributes on the Ember rootElement (for example, to drive dynamic per-route styling). In tests these attributes are added to the #ember-testing container and would be lost in the DOM hoisting, so we copy them to the to the snapshot's <body> tag to make sure that they persist in the DOM snapshot.