What is White Box Testing
A software testing technique that evaluates the working of an
application software by testing the functioning of its source code
and its internal structure.
- The source code is accessible or visible to the software
testers and needs to be tested. So, programming knowledge or
skills are inevitable for software testers.
- Every line of the source code is tested here which
ultimately results in inspection of the inner working of the
entire software system.
- Software developers also do white box testing as this
involves testing of the functioning, structure and working
flow of the source code. Software developers do this mostly
- fixing a bug, or
- after the completion of a new functionality or feature
or a module, and
- before the changes are submitted for the software
testers to test further.
Advantages of White Box Testing
The advantages of white box testing can be briefly summarized as,
- Very meticulous as it tests the entire source code and structure
—> The transparency of the internal code structure is beneficial
as it helps to identify the type of input data needed for
- Code optimization occurs as a result of white box testing and
the lines of code which are error- prone and not required or not
significant gets removed.
- This type of testing can be started at an earlier stage without
waiting for the completion of development.
- The test cases for white box testing are easy to automate.
- Communication burden between software developers and software
testers gets reduced as software testers performing white box
testing are expected to possess knowledge in programming
languages and skills.
White Box Testing Process
White box testing begins by scrutinizing and understanding the source
code, its design and structure, corresponding to the application
software to be tested, so that proper test cases can be created.
1. Familiarizing the Source code:-
- The software tester should familiarize with the internal source
code, its structure and its process flow.
“The tester should also be well versed with
programming language used to develop the
- The different functionalities embedded in the application should
be understood through its source code. This will be helpful in
identifying and creating different test cases for testing the
- The tester should be aware of secure coding practices as
security is a major concern while testing an application.
2. Make Test Cases and Execute them:-
- Test cases for each process in the application software to be
tested are created and executed by the software tester either
manually or after automating it through scripts.
- Test cases for every single path in the working flow of the
source code are created and executed.
- The results are analysed and recorded after executing the test
Types of White Box Testing
White Box testing includes different testing types which are used to
evaluate an application software.
i. Unit Testing:-
- Tests a Unit, which is the smallest block of code that can be
logically used for a purpose. Unit testing ensures the proper
functioning of each component of the source code as intended.
ii. Mutation Testing:-
Based on modifications or mutations made to the source code to
examine if the test cases executed can reveal bugs in the code.
- If all the test cases fail, then the source code tested is
- If any of the test cases passes the test, it signifies an error
or bug in the source code.
iii. Integration Testing:-
Intended to check the combined working of different
Units/Modules/Components of the application’s source code.
- Ensures that the modules that worked correctly independently are
also working fine when combined.
"The purpose of this
type of testing is to expose any errors in the interaction
of different units when associated together."
White Box Testing techniques
White box testing aims to scrutinize the source code of an application
1. Code Coverage Analysis:-
- Identifies areas of a program that are not yet tested by the set
of test cases created and executed. After identifying these
gaps, further test cases are created to test and verify the
untried parts of the code.
white box testing techniques related to Code Coverage are
Statement Coverage, Branch Coverage, Path Coverage, Function
Coverage, Condition Coverage and Multiple Condition
5. Function Coverage:-
- Evaluates the defined functions within the source code. Required
input parameters are passed to these functions to examine if the
working of each function is logical as intended.
6. Condition Coverage:-
- Evaluates the variables or expressions in a conditional
statement. The end result of each logical condition is evaluated
and tested here.
7. Multiple condition coverage:-
- Evaluates all the different combinations of the possible
outcomes of conditions for a decision to be made.
The ease and speed with which white box testing can be executed depends
on the size of the application software being tested. Small applications
can be tested fast but large applications may consume more time.
- Since the testing happens through the source code of the
application, maximum structural loopholes and bugs can be
identified at a profound level.
- Software developers and QA personnels can bring greater
efficiency, accuracy, and cost-effectiveness to white box
testing through its automation.
- Because white box tests can be automated, they can be executed
in CI pipelines to provide faster feedback for the software
developers while evaluating the source code.
- White box testing is widely used in the software industry
especially for applications dealing with high risk or critical