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What is Black Box Testing – HelpingTesters

September 18, 2017
Black Box Testing, Black Box Testing meaning, Black Box Testing techniques, Black Box Testing types

Black box testing or functional testing or behavioral testing or structural testing is a testing technique or method in which tester is not aware of internal structure / design / implementation of the application and tester is supposed to check the functionality of the application based on the requirement knowledge he/she is having. Since the tester is not aware of internal algorithms or code structure of the application, the application is like the black box to him/her. 

Black box testers only focus on expected output after giving the variety of inputs to the system/ application. The input may be in the form of keystrokes and clicks also, to verify what happens after performing these operations. Technical features are hidden from the testers. When and undesirable output follows the input, a bug is reported. Test cases are developed according to software specifications like functionality, usability, and performance.


⇒ Advantages of Black Box Testing

  • The tester can be non-technical and need not learn a programming language to test the functionality of the application.
  • Verification of the contradictions in actual systems and specifications.
  • Black box testing can help in developing software in a more user-friendly way than mentioned in requirement document as a tester is supposed to test the application from user’s point of view.
  • Testing can be done once the application is released by the development team and does not have any dependency on the development team for testing.
  • Once the functional specification is complete, test cases can be designed.

⇒ Disadvantages of Black Box Testing

  • There are chances of leaving unidentified conditions in absence of knowledge of programming structure.
  • In short span of time, it is quite difficult for the testers to identify all possible inputs to write test cases for a particular scenario and test it.

⇒ Software test life cycle for Black Box Testing

  • Requirement – In this stage, the requirement regarding the software application to be tested is gathered to start testing.
  • Test planning– In this stage, the test plan is developed containing the description of how to proceed to test.
  • Analysis– Analysis is done to consider things like feasibility, risks, and mitigation plan etc.
  • Design– In this stage, a test case is designed and also automation test script is developed (if required), as per the requirement specification and business need.
  • Test execution: In this stage, test cases are executed and automation test script is run (if required). Regression testing and retesting of the issues or bug is done before test closure.
  • Regression testing: After the test is executed, defects are reported to the development team. After defects are fixed by the development team, it is again tested by the tester to verify if a defect has been fixed otherwise again reported to development team till it is fixed and the defect is closed. Regression testing also ensures that defects fixed by developer do not have any impact on other parts of the software before the release of the software application. Regression testing also reports the defect which arises due to new functionality added in the recent build.

Black box testing is done in almost all levels of testing except unit testing and white box testing. Black box testing is done in following levels of testing

  • Integration testing
  • System testing
  • User acceptance testing

Black Box Testing Techniques

Some of the techniques used for designing black box test are as below:

  • Equivalence Partitioning

This testing technique divides whole input range into partitions which can be a valid partition and invalid partition. The idea behind this partition is to test each partition once. So the assumption is that any input within the partition or range is equivalent and give the same result and produces the same output.

  • Boundary Value Analysis

This test design technique involves testing of data on the boundary as well as testing adjacent data on each side of the boundary defined as input data range or in other words, we can say that this design technique involves testing of data on the boundary as well as adjacent value inside/ outside of the boundaries. Boundary value analysis test design technique is based on assumption that the system behaves differently on either side of a boundary.

  • Cause Effect Graphing

The Cause Effect graph black box testing technique shows the relationship between given output and the factors that influence the output graphically. Cause stands for input condition that brings an internal change in the system. Effect represents an output condition, system state resulting from a combination of causes. By studying cause and effect, cause effect graph can be prepared which helps in preparing test cases

  • Error Guessing

This test design technique is based on experience based testing. Domain expert tester who is having good experience of testing the specific type of software, are in better position to find out bugs which repeatedly occurs in such type of software. Domain expert testers are able to find out defects with less effort and in less time.

Overall, we can say that black box testing is a type of testing in which tester test the software application matching the actual output with the expected output without knowing the internal algorithm of the software.

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