This article is posted by IBM and explains how the Mock Object can be used. In this article we will find some of the benefits of using Mock Objects for writing Unit tests for objects that act as mediators. Unit testing has become widely accepted for software development. When you write an object you must also provide an automated test class containing methods that put the object through its paces, calling its various public methods with various parameters and making sure that the values returned are appropriate.When we're dealing with simple data or service objects, writing unit tests is straightforward. However, many objects rely on other objects or layers of infrastructure. When it comes to testing these objects, it is often expensive, impractical, or inefficient to instantiate these collaborators. For example, to unit test an object that uses a database, it may be burdensome to install, configure, and seed a local copy of the database, run your tests, then tear the local database down again.A mock object conforms to the interface of the real object, but has just enough code to fool the tested object and track its behavior. For example, a database connection for a particular unit test might record the query while always returning the same hardwired result. As long as the class being tested behaves as expected, it won't notice the difference, and the unit test can check that the proper query was emitted.
Here are some of the common coding style for testing with mock objects:
- Create instances of mock objects
- Set state and expectations in the mock objects
- Invoke domain code with mock objects as parameters
- Verify consistency in the mock objects
Citation
https://www.ibm.com/developerworks/library/j-mocktest/
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