Failed attempt at promise matchers wrapper for jasmine 2

promiseMatchers.js

beforeEach(function () {
  jasmine.Matchers = {prototype: {}};
  jasmine.Env = {prototype: {}};
  require('promise-matchers');

  Object.keys(jasmine.Matchers.prototype).forEach(function(key) {
    var matcher = jasmine.Matchers.prototype[key];
    jasmine.Matchers.prototype[key] = function() {
      return {
        compare: function(actual, done, expected) {
          actual.toString = function() { return 'Promise'; };
          var self = {
            actual: actual,
            env: jasmine.Env.prototype
          };
          return {
            pass: matcher.call(self, done, expected)
          };
        }
      }
    }
  });

  jasmine.addMatchers(jasmine.Matchers.prototype);
});