Protractor toContainClass custom matcher

gistfile1.js

beforeEach(function() {
  this.addMatchers({
    toContainClass: function (expected) {
      var self = this;
      var deferred = protractor.promise.defer();

      self.actual.getAttribute('class').then(function(classes) {
        var result = classes && classes.search(new RegExp(expected, 'i')) > 0;

        if (result) {
          deferred.fulfill(true);
        } else {
          deferred.reject(classes + ' did not contain class ' + expected);
        }
      });

      return deferred.promise;
    }
  });
});