November 29, 2012

Black Box Testing

Black Box Testing - QAInsights

Understanding the basics thoroughly helps to become expertise in any field. In this blog post, we will see about Black box testing techniques. Black box testing is also called as Behavioral Testing or Specification based Testing or Business-Transaction driven Testing.

What is Black box testing?

Black box testing is one of the Dynamic Testing techniques. It is used to validate the business requirements and system functionality. Test cases are designed ad executed on external specifications without knowledge of how the system has built. Testers do not consider about the internal behavior of the code and the program structure.

Black Box Testing - QAInsights

Black Box Testing Diagram

Consider a text field which should accepts only number between 18 and 100. It is not possible to write and execute test cases with input data from 18 to 100. It will be time consuming and eats up testers’ effort.

Black box techniques help to optimize the test cases with relevant input data to test. There are three black box testing techniques.

  • Boundary Value Analysis
  • Equivalence Partitioning
  • Error Guessing

Boundary Value Analysis

Boundary Value Analysis (BVA) is a Black box testing technique to optimize the input data for writing test cases. BVA focuses on boundary values of the input data. It has Lower Limit, On the boundary and Upper Limit.

E.g. Credit Card Cash Limit should be from 1000$ to 5000$. Boundary Value Analysis yields:

Boundary Value Analysis Table - QAInsights

Boundary Value Analysis Table

Tester should consider only the boundary values of lower and upper limit and on the boundary values while Test Case Design.

Equivalence Partitioning

Equivalence Partitioning is a Black box testing technique to optimize the input data for writing test cases. Equivalence Partitioning is technique which helps testers to consider only data from equivalence classes instead of exhaustive values in the larger class.

E.g. Credit Card Cash Limit should be from 1000$ to 5000$. Equivalence Partitioning yields:

Equivalence Partitioning - QAInsights

Equivalence Partitioning

Tester should consider only the values in Invalid Classes and Valid Class while Test Case Design.

Error Guessing

Based on the tester experience and intuition test cases can be designed. E.g. Tester can easily identify defects while testing date fields.

Download our simple Boundary Value Analysis and Equivalence Partitioning tool which helps you to understand the concept.

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About NaveenKumar Namachivayam

Hi there! is a passionate and experienced Performance Test Analyst based in Chicago, USA with skill sets in Manual Testing, Test Automation, Performance Testing, and Test Estimation. He loves to learn and experiment new trends and models in Software Testing. Please stop by at his personal blogs: Excel Blog, DealsBrook,, and Affiliate Insights blog and Software Testing Memes.

2 Comments on “Black Box Testing

December 14, 2012 at 2:49 pm

My own take on black box testing is that you need end-users to perform the testing, people who are not necessarily technical. You need someone to represent how the software is likely to be used. For them, it truly is a “black box”. They type the data in one screen and hope to get the right report the right way from another screen. The trick, then, is to nudge those people into truly thinking through all the business circumstances they are likely to encounter so that they apply those real-world situations to the code you want tested. I use the work ‘trick’ because you don’t want to spoon feed everything as that defeats the purpose. The purpose, of course, is to find out what you missed.
I also recommend you to read the fo0llowing article on this:

December 17, 2012 at 1:39 pm

Many thanks Daisy! I agree with your comments. Let me check your link.

Thank you,
NaveenKumar N


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