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Monday, July 9, 2012

List out the technical details of mock object?

Mock objects are much in talk these days and seem to be marking themselves as one of the effective tools in carrying out unit testing. 

What are Mock Objects?

- Mock objects are simulated objects counterparts of the original or the non mock object that is intended to mimic the behaviour and working of the original non mock object in a way that is controlled and defined. 
- Classes with heavy code bases are such a pain to test and can be tested only by the mock objects. 
- Ever tried implementing unit tests in a project but failed to do so because of the dependency of the module and difficulty in its isolation?
- Within a budget and time constraint it becomes difficult for configuring and setting up all the external dependencies of the modules. 
- Mock objects are a feasible option for overcoming such problems. 
- Problem with most of the mock tools is that they do not come with documentation so it becomes difficult to work them out. 
- These technical details of mock objects are the center point of this article. 
- Since the mock objects simulate the real object, they are said to possess the same interface as that of the real objects that they are imitating. 
- Nowadays many mock object frame works are available using which the programmers and developers can specify which all methods are to be invoked by the mock object and in which order. 
- Also, the parameters that have to be passed to the mock object can be specified along with the values that will be returned by the mock object. 
- We have divided the technical details of the mock objects in to three categories:
1. Mocks, fakes and stubs
2. Setting expectations
3. Writing log strings

Mocks, fakes and stubs: 
- Some consider the mock objects and fakes to be different things saying that the fakes are much simpler than the mock objects. 
- The fakes are simply used to represent just the interface of the object which they are mimicking and responses that they return are pre-arranged. 
- Thus, we can say a set of method stubs is provided by the fake objects. 
- On the other hand, the mock objects are fake objects but they help in determining whether some other object passes or fails the test to which it is subjected. 
- It does so by the verification whether of the interaction if any took place on the object. 
Everything else apart from these two i.e., fake objects and mock objects is considered to be a stub. 
- Stub is anything unreal is fake and based up on its usage it can be classified as stubs and mocks. 
- Mock objects possess a little more functionality which is that their method implementations contain assertions that are truly theirs. 
- This furthermore implies that the context of each and every call is examined by the true mock object.
- The examination includes the checking of the order of calling of the methods and performing tests on the data that has been passed as arguments to the method calls.

Setting expectations: 
It is ensured by a mock setting that the calls to the system will cause the system to throw some exception like getting hanged or crashing.

Writing log strings: 
Mock methods can be used to make an entry to the public log strings which otherwise could result in invisible performance sapping bugs.

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