Test automation has become an indispensable part of software development. But writing and running tests against complex systems can be hard. This is where mocking and stubbing come in. In this article we look at what mocking and stubbing are, how they are used, and what they buy you.
What Is Mocking?
Mocking is the process of creating fake objects that imitate the dependencies of the unit under test. These fake objects simulate the behavior of the real ones, but they respond in a controlled way.
How Do You Use Mocking?
- Identify the unit to be tested.
- Determine the unit’s dependencies.
- Create mock objects for those dependencies.
- Define the expected behavior of the mock objects.
- Run the test and verify the results.
What Is Stubbing?
Stubbing is replacing the behavior of a method or function with a fixed, predetermined response. Stubs are usually simpler and carry less functionality.
How Do You Use Stubbing?
- Identify the method to be tested.
- Define the method’s expected inputs and outputs.
- Create the stub object and set the expected behavior.
- Run the test and check the results.
Advantages of Using Mocks and Stubs
- Isolation: Tests become independent of one another, which makes debugging easier.
- Speed: Tests run faster because fake objects are used instead of real ones.
- Control: You can build test scenarios more easily and more precisely.
- Stability: You get consistent test results that aren’t affected by external factors.
- Cost Savings: Simulated environments cost less than standing up real systems.
- Coverage: You can test scenarios that would otherwise be hard to reach.
Mocking and stubbing are essential tools in test automation. With them you can write more reliable, faster and more thorough tests, and raise the quality of your software. But as with any technique, use them in balance and in the right places. Overuse pulls your tests away from real-world scenarios.