Introduction:
AngularJS projects, it’s common to use promises to handle asynchronous operations. However, when writing tests, you may encounter situations where you need to mock a promise and its associated methods. This blog post will guide you on how to mock a promise in a Selenium-Karma test and address the specific issue of “Cannot read property ‘success’ of undefined.”
Understanding the Problem:
The error message “Cannot read property ‘success’ of undefined” suggests that the mocking of the promise is not set up correctly in the test case. The code snippet provided shows an attempt to create a fake service method that returns a promise with the ‘success’ method. However, something seems to be missing, leading to the error.
Solution:
To resolve this issue, we need to adjust the way the promise is mocked in the beforeEach function. Instead of manually adding a ‘success’ method to the promise, we can leverage AngularJS’s built-in $q service to create a resolved promise. Here’s how you can update the mocking code:
code
beforeEach(function() {
spyOn(ServerService, 'methodName').and.returnValue($q.resolve());
});
By using returnValue($q.resolve()), we instruct the mocked methodName to return a resolved promise without any specific data. This approach eliminates the need to define a ‘success’ method on the promise, as it is deprecated in newer versions of AngularJS.
Updating the Test Case:
Now that we have fixed the mocking issue, let’s update the test case to verify the behavior:
code
it('should test the save method', function() {
// Test assertion stuff
expect(ServerService.methodName).toHaveBeenCalledWith(param1, param2);
});
In this updated test case, we can expect that ServerService.methodName is called with the correct parameters. This ensures that the method is invoked correctly within the code under test.
Conclusion:
In this blog post, we addressed the issue of “Cannot read property ‘success’ of undefined” when mocking a promise in a Selenium-Karma test. By using the $q service and returning a resolved promise, we can effectively mock the desired behavior without relying on deprecated methods. Remember to update your test cases accordingly to verify the correct invocation of the mocked method.
I hope this solution helps you overcome the error and enables you to proceed with your testing successfully. If you have any further questions or need assistance, feel free to leave a comment below.
