feat(jasminewd): better error messaging when expect is called with a WebElement

Previously, using expect() with a web element would cause the webdriver
jasmine adapter to go into an infinite loop trying to resolve the promise,
since WebElement inherits from Promise but resolves to itself. Now
throws a more readable error.

Closes #178.

Author: juliemr

jasminewd/index.js

@@ -104,6 +104,10 @@ originalExpect = global.expect;
 
 global.expect = function(actual) {
   if (actual instanceof webdriver.promise.Promise) {
+    if (actual instanceof webdriver.WebElement) {
+      throw 'expect called with WebElement argment, expected a Promise. ' + 
+          'Did you mean to use .getText()?';
+    }
     return promiseMatchers(actual);
   } else {
     return originalExpect(actual);

jasminewd/spec/adapterSpec.js

@@ -10,6 +10,9 @@ var webdriver = require('selenium-webdriver');
 var getFakeDriver = function() {
   var flow = webdriver.promise.controlFlow();
   return {
+    controlFlow: function() {
+      return flow;
+    },
     sleep: function(ms) {
       return flow.timeout(ms);
     },
@@ -108,6 +111,14 @@ describe('webdriverJS Jasmine adapter', function() {
     expect(fakeDriver.getBigNumber()).toBeLotsMoreThan(33);
   });
 
+  it('should throw an error with a WebElement actual value', function() {
+    var webElement = new webdriver.WebElement(fakeDriver, 'idstring');
+
+    expect(function() {
+      expect(webElement).toEqual(4);
+    }).toThrow('expect called with WebElement argment, expected a Promise. ' +
+        'Did you mean to use .getText()?');
+  });
 
   // Uncomment to see timeout failures.
   // it('should timeout after 200ms', function() {