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Unit 3: Black Box Testing

the behavior of the code when some modification is made to the original code. Depending on the
behavior of the system, bugs can be found in the software, after the modifications are made to the
original software. Mutation testing is carried after the test software has cleared the preliminary test and
is found bug free. The mutation can vary from a simple change of operator name or variable name to
replacing the logical operator with its inverse. A complex mutation involves changing the order of
execution of the code or removing some lines of codes.
The expression,
a !=b;
can be mutated as,
a ==b;

After the mutation, the software is executed to record the output of its behavior. The test cases used are
those which have been created during preliminary testing. If the test cases are well written, the
mutated program should fail. However, if it clears the test case, either the test case is weak which has to
be re-checked or the program has bugs.

Black Box Testing for Banking Applications

A
global banking firm with over 30 million customers wanted to increase its business
volume by concentrating more on customer retention and enhancing relationship with
them. For this the bank used client-server applications for their banking software.
Every client server application needs continuous up-gradations to facilitate integrated transactions
from common servers and reworking navigation and usability that meets business needs. Any failure
or errors in such applications may lead to severe financial losses to the customers and the bank. This
also affects the reputation of the bank. The bank provides various deposit and loan products,
automobiles finance, housing loans and personal loans for their customers across the globe. Bugs in
the software might cause problems related to availability, scalability, and performance. They have to
be resolved before the application reaches the production environment.

A team of highly skilled testers were given the task of testing the banking application. Subject Matter
Experts gave extensive knowledge and training to the team to make the testers aware of the bank's
business requirements. The testing team developed a high level test plan, and designed business
scenarios, which were extensive black box testing test scenarios to test the application. The team ran
these test cases and scenarios in a configured environment with end-user perspective to detect critical
bugs in the application.
Based on the test case results, the team suggested up-gradation in the application. Since the test cases
were domain specific and end user oriented, the team was able to efficiently carry out the testing
process. Therefore, with the help of extensive black box testing, the testing team was able to address
all the concerns of the bank successfully.
This extensive black box testing helps to:
1. Measure the factors that affect the performance of the application.
2. Provide confidence to the bank in the application’s performance before it is deployed in the
actual working environment.
3. Establish performance standards for all the applications and monitor critical indicators to assess
the change in the expected performance levels.

Questions
1. What was the problem that the bank faced? How was it addressed?
2. Do you think extensive black box testing helped the bank to resolve the issue that it was facing?
Adapted from (http:// www.lntinfotech.com/casestudies/testing/reduction_in_testing_costs.pdf)

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