Page 36 - SOFTWARE TESTING & QUALITY ASSURANCE

Unit 3: Black Box Testing

4. This type of testing cannot be focused on specific segments of function that may be very complex,
therefore bugs can go undetected.
When there is a complex system to be tested like the online Indian railways
booking system, it is difficult to identify tricky inputs and write test cases to
cover all possible scenarios. .

Performing a black box test, the tester attempts to find the following errors based on
the behavior of the software:
Missing or incorrect functionality.

1. Errors in interface.
2. Data structure errors.
3. Performance errors.

4. Initialization and terminal errors.

As a part of black box testing strategy, it is very important to use test monitoring tools.
This is needed to track the tests that have already been executed, to avoid repetition and
to aid in the software maintenance.
3.1.2 White Box Testing
White box testing is also called as glass box testing. In this test, the tester focuses on the structure of the
software code. The tester develops test cases to check the logical working of the software code.

Black box testing helps to answer the validation question "are we building the right software?", but
white box testing helps to answer the verification question "are we building the software right?"
White box testing helps the tester to check how exactly the calculator performs
the addition of two numbers and if it is the efficient way to perform the
addition operation.
In white box testing, each software module is tested independently. The tester has to develop test cases
not only to test the individual module of the software, but also to test how exactly the modules interact
with each other when software is executed. All the tests are carried out at the source code level. The
tester checks all the parameters of the code such as efficiency of the code written, branching statements,
internal logic of the module, interfaces between external hardware and internal module, memory
organization, code clarity, and so on. Therefore, the test cases must be carefully designed in order to
cover the internal working of the application.

The tester who writes the test cases to perform white box testing has to be very well
aware of the language and logic used to develop the test software. He/she needs to
know programming concepts as well.
Advantages of White Box Testing
1. As the tester has the knowledge of internal coding, it is very easy to develop test cases to test the
software effectively.
2. Testing is carried out at the code level; hence it helps in optimizing the code.
3. Unnecessary or extra lines of code which can generate hidden bugs can be removed.

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