Black Box Testing – A Practical Guide for all Beginners

Black Box Testing is a software testing strategy which verifies the behavior of a system from the outside without knowing its internal design or implementation details. Hence, it has got another name as Behavioral Testing. It mostly examines the functional aspects but does cover some of the non-functional areas as well.

Black Box Testing of a Software

In this type of testing, the software got treated as a black-box which means that it can only be seen, observe or use from the outside. That’s why this method got famous with names like a Black box or behavioral testing. IT helps the testers to reveal the following types of errors:

  • Incorrect functions or gaps in functionalities
  • User interface issues
  • Improper use of data structures or databases
  • Usability errors
  • Performance bottlenecks
  • Unexpected failures at startup or abrupt finish

Black box Testing as per ISTQB

ISTQB represents the International Software Testing Qualifications Board. It is a non-profit Belgium based organization which contributes to global testing standards and provides testing certifications. Let’s hear how does ISTQB define the Black box Testing?

Black box Testing:

It is a testing methodology which could either be functional or non-functional and doesn’t require any reference to the internal structure of the software for execution.

Black box Test Design Process:

Test design and selection is entirely based upon the functional or non-functional specifications and happen independently without needing any details of the internal structure.

Black box Test Scenario:

A testing professional who is not aware of the internal data structures and implementation of an e-commerce portal examines the different pages by navigating them in a browser, performs actions (open/click links) and checking the results and matching with the expected behavior.

Black box Testing Applies to:

This method touches upon the following areas of manual testing:

1- Integration,
2- System, and
3- Acceptance

As the level goes higher and higher, more becomes the complexity of the box.

Black box Testing Techniques:

There are a bunch of popular black-box testing methods which a tester can learn to perform.

1. Equivalence Partitioning:

It is a commonly used black box testing technique for designing test cases that suggest dividing data values into right and wrong partitions and picking representational values from each partition as test input data.

2. Boundary Value Analysis:

It is a manual testing design technique that requires the following:

1. Calculation of boundaries for input data values, and
2. Choosing values that are on edge and directly inside/outside of the borders as test data.

3. Cause-Effect Graphing:

It is a simple test design technique that requires distinguishing the cases (input conditions) and outcomes (output conditions), drawing a Cause-Effect Graph, and forming test cases accordingly.

Black box Testing Benefits:

1. Tests take care of the user’s perspective and assist in revealing the inconsistencies in the specifications.
2. Tester doesn’t have to know the programming languages or the technologies used for developing the software.
3. Test execution can happen independent from the developers, providing a subjective aspect and eliminate any biases.
4. Test case generation can start once the specifications are in place.

Black box Testing Drawbacks:

1. The test data is small and can only cover limited paths causes parts of the program untested.
2. Test designing is not easy when no clear specifications are available.
3. Tests can be repetitive if the programmer has already got them covered in his unit test cases.
4. Execution in black box testing is somewhat like a soothsayer shuts his eyes while foretelling events.