A Comprehensive Guide to Black Box Testing

Timothy Joseph
Timothy Joseph
| June 9, 2020

A Comprehensive Guide to Black Box Testing

Behavioral testing, opaque-box testing, closed-box testing, specification-based testing, eye-to-eye testing - yes, there are quite a few alternate names for the practice of black box testing.

No matter what you call any of these approaches of black box testing, it maintains its essential status from project to project, from one development cycle to the next.

But what is black box testing? What is the purpose of black box testing? And when is it right to use black box testing?

Let’s take a closer look at the role black box testing can play in your internal testing practices.

What is Black Box Testing?

Black box testing is a software testing method where the tester does not know the internal structure, design and/or implementation of the software product requiring testing. The best time to use black box testing is when testers are required to create and execute test cases but have no access to the application’s source code.

Think of black box testing like a black box. A tester from the outside cannot see what the black box holds on the inside. The tester must discover what’s missing or what’s broken through running test cases designed to uncover these defects or errors.

What is the Purpose of Black Box Testing?

The purpose of black box testing is to see if the application satisfies the customers expectation of the software product experience. Black box testing is used to uncover the following errors within the software product:

  • Errors in data structures or external database access
  • Interface errors
  • Behavior and performance errors
  • Incorrect or missing functions
  • Initialization and termination errors

What are the Types of Black Box Testing?

There are two main approaches of black box testing. While opposite in approach, both types of black box testing should be performed to verify the soundness of the software system before market launch.

  • Functional Testing focuses on the functional requirements and specifications of the software product. It tests the behavior of the application and verifies whether or not it performs as expected. Functional tests executed during black box testing include:
    • Smoke testing: Do the critical functions of the system perform correctly?
    • Sanity testing: Do the new functions of the system perform correctly?
    • Integration testing: Do units and modules within the system work together seamlessly?
    • Regression testing: Does existing functionality of the system perform correctly?
    • Localization testing: Does the system perform as expected for target regions or locales?


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  • Non-functional Testing focuses on all other aspects of the software product. It tests the quality of the application, particularly the accuracy, time, correctness, stability and durability of the application across various situations. Non-functional tests executed during black box testing include:
    • Load testing: Does the system perform as expected with multiple users during normal circumstances?
    • Stress testing: Does the system perform as expected during high peak usage?
    • Usability testing: Is the User Interface intuitive and user-friendly?
    • Compatibility testing: Does the system perform as expected across all browsers, operating systems and devices?
    • Scalability testing: Does the system perform as expected when the number of user requests scales up or down?

What are the Different Black Box Testing Techniques?

A well-designed test case intends to be systematic, thorough and efficient. Testers can follow these four approaches of black box testing techniques in order to structure strong test cases and execute all required testing during the project.

  • Equivalence Partitioning: Divide input values into valid and invalid partitions, then select representative values from each partition as test data. This black box testing technique minimizes the number of possible test cases to an optimum level, ensuring reasonable test coverage during testing.
  • Boundary Value Analysis: Focus on the values at boundaries to determine whether or not a certain range of values is acceptable by the system. This black box testing technique reduces the number of test cases and is most suitable for systems where the input is within specific ranges.
  • Decision Table Testing: Identify the test cases as input conditions and the effects as output conditions to produce a cause-effect table. This black box testing technique analyzes every object relationship so that test cases can be written appropriately to uncover defects.
  • Error Guessing: Apply previous experience with the application behavior and functionalities to hypothesize error-prone areas of the system. This classic black box testing technique relies on a tester’s familiarity with the application as well as with the development team’s programming approach.

Best Tools for Black Box Testing

These approaches of black box testing cannot enhance test result accuracy without the assistance of automated tools designed for black box testing. The right automated testing tool can streamline the testing process, thus supporting best agile development practices. We recommend checking out these black box testing tools to see which automated testing tools are the right fit for your team.

Advantages of Black Box Testing

Successful teams apply various approaches of black box testing within their QA practices because of the results these kinds of tests deliver. You can expect to enjoy these advantages of black box testing once it’s implemented within your internal team practices:

  • No technical background required: Testers do not need any knowledge of programming languages or understanding of software implementation to test. Therefore, you can potentially have a large group of black box testers.
  • Ensure product quality: By testing from the user’s point of view, your testers can more easily expose discrepancies within the experience and product specifications.
  • Independent test execution: Once development is complete, testers can start testing immediately without relying on the development team for input or guidance.
  • Earlier detection of defects: Black box testing allows testers to discover issues and errors within the system sooner, so that the development team has time to apply fixes before market launch.

Disadvantages of Black Box Testing

Your team will notice certain downsides to black box testing, despite the insight gains received from its substantial benefits. Expect some of these disadvantages of black box testing to occur throughout your testing cycle so that your team can strategize a solution to combat each issue:

  • Lack of technical understanding: Since there’s no visibility into the source code, testers can often miss testing certain conditions or scenarios.
  • No complete test coverage: Because black box testing is designed to cover a reasonable amount of test case possibilities, testing is not comprehensive and cannot guarantee an error-free product before launching to market.
  • No clear specifications: Test cases are difficult to structure without any guidance from the development team on direction or intention.
  • Redundant testing: A QA tester can run the same test case already executed by a software developer due to no insight on the development process

Need some guidance to implement black box testing? You can choose to partner with a QA services provider like QASource. Our 800 experienced engineers are skilled in all approaches of black box testing and are well-versed in executing automated testing across functional and non-functional test cases. With our team of experts, your business can onboard black box testing within your internal practices faster so that your team can realize more accurate testing results and retain software product quality. Get in touch with a QASource expert today.

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This publication is for informational purposes only and nothing contained in it should be considered legal advice. We expressly disclaim any warranty or responsibility for damages arising out of this information and encourage you to consult with legal counsel regarding your specific needs. We do not undertake any duty to update previously posted materials.