Introduction to Object Oriented Testing Methods

Object oriented testing begins in the small with a series of tests designed to exercise class operations and check whether errors exist as one class collaborates with other classes. Use based testing along with fault based testing is applied to integrated classes. In the end, use cases are used to uncover errors at software validation level.

Encapsulation can create a minor problem when testing because testing reports on concrete and abstract state of an object. Multiple inheritance complicates testing by increasing number of contexts for which testing is required. Black box testing methods are appropriate for object oriented systems as they are for systems developed using conventional software engineering methods.

The strategy for fault based testing is to hypothesize a set of possible faults and then derive the tests to prove each of that hypothesis. The effectiveness of these techniques depends on how testers see a plausible fault.

Inheritance complicates the testing process. even though the base class has been properly tested, there is a need to test all classes derived from it.

Scenario based testing will uncover errors that occur when any actor interacts with the software. It concentrates on what the user does and not what the product does. This type of testing uncovers interaction errors.

Surface structure is an externally observable structure of object oriented program. Testing surface structure is similar to black box testing. Deep structure refers to the internal technical details of object oriented program. It exercises dependencies, behaviors and communication mechanisms. It is similar to white box testing.

What are different elements of the analysis model?

Analysis model provides description of required information, functional and behavioral domains of computer based systems. There is a set of generic elements that is common to most analysis models:

- Scenario based elements are the first part of the analysis model that is developed. They serve as input for creation of other modeling elements. In another method for scenario based modeling, if we use functions or activities that would have been defined when the requirements elicitation was being done. These functions are a part of the processing context. When you have the analysis model, you would have defined a sequence of activities and these activities in turn describe the processing within a limited context. As stated earlier in previous post, when you take the analysis model, activities can be described at multiple levels of abstraction.

- In class based elements, a usage scenario has a set of objects which are categorized into classes which is a collection of things that have similar attributes and common behavior.

- In behavioral elements, the behavior of a system effects the chosen design and implementation approach that is applied. A state is an externally observable mode of behavior. State diagrams represents behavior of system depicting states and events that cause system to change state.

- In flow oriented elements, information flows through a computer based system. System accepts input,transform them using functions and produces output.

Understanding Scenario Based Testing

Scenario based tests (SBT) are best suited when you need to tests need to concentrate on the functionality of the application than anything else.
Suppose, you are testing an application which is quite old and it is a banking application. This application has been built based on the requirements of the organization for various banking purposes. Now, this application will have continuous upgrades in the working.
Let us assume that the application is undergoing only functional changes and not the user interface changes. The test cases should be updated for every release. Over a period of time, maintaining the test ware becomes a major set back. The Scenario based tests would help you there.
As per the requirements, the base functionality is stable and there are no user interface changes. There are only changes with respect to the business functionality. As per the requirements and the situation, it is clearly understood that only regression tests need to be run continuously as a part of testing phase. Over a period of time, the individual test cases would become difficult to manage. This is the situation where we use scenarios for testing.
To derive scenarios, the following can be used as a basis:
- From the requirements, list out all the functionality of the application.
- Using a graph notation, draw depictions of various transactions which pass through various functionality of the application.
- Convert these depictions into scenarios.
- Run the scenarios when performing the testing.

Scenario based tests are not only for legacy application testing, but for any application which requires you to concentrate more on the functional requirements. I f you can plan out a perfect test strategy, then the scenario based tests can be used for any application testing for any requirements. Scenario based tests will be a good choice with a combination of various test types and techniques when you are testing projects which adopt UML (Unified Modeling Language) based development strategies.