What is Black Box Testing?

Firstly we will learn what is Black Box Testing? Here we will discuss about how black box testing is perform, different BBT Techniques used in testing.

Black Box Testing Method:

Black box testing is the Software testing method which is used to test the software without knowing the internal structure of code or program.

Most likely this testing method is what most of tester actual perform and used the majority in the practical life.

Basically software under test is called as “Black-Box”, we are treating this as black box & without checking internal structure of software we test the software. All testing is done as customer’s point of view and tester is only aware of what is software is suppose to do but how these requests are processing by software is not aware. While testing tester is knows about the input and expected output’s of the software and they do not aware of how the software or application actually processing the input requests & giving the outputs. Tester only passes valid as well as invalid inputs & determines the correct expected outputs. All the test cases to test using such method are calculated based on requirements & specifications document.

The main purpose of the Black Box is to check whether the software is working as per expected in requirement document & whether it is meeting the user expectations or not.

There are different types of testing used in industry. Each testing type is having its own advantages & disadvantages. So fewer bugs cannot be find using the black box testing or white box testing.

Types of Black Box Testing Techniques: Following black box testing techniques are used for testing the software application.

  • Boundary Value Analysis (BVA)
  • Equivalence Class Partitioning
  • Decision Table based testing
  • Cause-Effect Graphing Technique
  • Error Guessing

1) Boundary Value Analysis (BVA):

Boundary Value Analysis is the most commonly used test case design method for black box testing. As all we know the most of errors occurs at boundary of the input values. This is one of the techniques used to find the error in the boundaries of input values rather than the center of the input value range.

Boundary Value Analysis is the next step of the Equivalence class in which all test cases are design at the boundary of the Equivalence class.

Let us take an example to explain this:

Suppose we have software application which accepts the input value text box ranging from 1 to 1000, in this case we have invalid and valid inputs:

Invalid InputValid InputInvalid Input
0 – less1 – 10001001 – above

Here are the Test cases for input box accepting numbers using Boundary value analysis:

Min value – 1


Min Value


Min value + 1


Normal Value

1 – 1000

Max value – 1


Max value


Max value +1


This is testing techniques is not applicable only if input value range is not fixed i.e. the boundary of input is not fixed.

2) Equivalence Class Partitioning

The equivalence class partition is the black box test case design technique used for writing test cases. This approach is use to reduce huge set of possible inputs to small but equally effective inputs. This is done by dividing inputs into the classes and gets one value from each class. Such method is used when exhaustive testing is most wanted & to avoid the redundancy of inputs.
In the equivalence partitioning input are divided based on the input values:

  • If input value is Range, then we one valid equivalence class & two invalid equivalence classes.
  • If input value is specific set, then we one valid equivalence class & one invalid equivalence classes.
  • If input value is number, then we one valid equivalence class & two invalid equivalence classes.
  • If input value is Boolean, then we one valid equivalence class & one invalid equivalence classes.

For More Details Go To The:What is Boundary Value Analysis and Equivalence Class Partitioning?” article.

This Post Has 25 Comments

  1. Installation laps completed, track is still damp in places. Corvettes now in pit lane waiting for track to dry before serious testing.

  2. Hi,
    What a comprehensive article on Black Box Testing article, cleared basic concept, Thank you very much sir!

    But I have one question “where do you derive the inputs for Black Box testing?”, this is asked in the interview please answer this question.

  3. good job! nice nice.

  4. what an nice info, keep posting to get updated information.

  5. Thank you! Excellent example!

  6. it is the very good articles and provided with very good basics knowledge of application testing. thanks

  7. I am preparing for interview, I have total about 1.3 yrs of experience. very very helpful article for tester like me. Thanks very much for great post!

  8. Most important topic for test engineers
    Thank you very much

  9. It is great every time i stumble on a really good publish like this. Getting a bit drained with the bad high quality posts a few bloggers create on their blogs. Hold it up. You now have a normal visitor now!

  10. very nice explanations

  11. Really very good content

  12. thank you so much!!

  13. what about error guessing techniique

  14. Kya baat hai.. waah made my day!!!!

  15. Unit testing comes under which one…. white box testing or black box testing?

  16. Article was so clear and easy to understand.

    @ Mukund :- Unit testing comes under White Box Testing because in Unit Testing we have to test the source code for a Module.
    In white box testing we have to know internal structure(coding) of a software and same we do in unit testing.



  19. Explained in a very simpal language and with comprehencive example
    Thanku …….

  20. it was vey useful for me to attend an interview ,Thanks a lot!!

  21. Very Very basic. I have never seen Such a detail .

  22. you are awesome

  23. thanks this is very good artical.but ihave one dought sove anakytical question examples

  24. How to Build test plan for black box testing?

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