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What is Black Box Testing?

Author: Joe Schulte

Diagram of Black Box Testing showing input and outputs through a system under test

Overview


Black Box Testing, also known as behavioral testing, is a way to test software functionality without diving into a system’s source code and inner workings. Black Box Testing validates software functionality by using inputs and outputs based on various software requirements. This enables engineers to test hardware-software integration and the overall functionality of a system.


While Black Box Testing is primarily used to test functionality, it can also be used for non-functional test purposes such as load testing, stress testing, or performance testing. In our lab at Array of Engineers, we have used Black Box Testing to develop, test, and understand embedded software functionality for projects in the aerospace, defense, medical device, and space sectors. We have also used Black Box Testing for our own custom hardware systems, cable harnesses, programs, applications, and APIs at Array of Engineers.


Types of Black Box Testing


  • Functional Testing - Functional testing is a type of software testing that determines whether software features meet the needs of software requirements. By matching up and comparing features with requirements, you can determine whether software meets the expectations of the end user. Black Box Testing can be used to test certain hardware and software functions of the system under test. These tests can include unit testing, integration testing, smoke testing, system testing, and user acceptance testing.

  • Non-functional Testing - Non-functional software testing analyzes software performance, accessibility, and its overall user experience. Some examples of non-functional testing include API testing, maintainability testing, usability testing, and security testing. Black Box Tests can test an application’s performance under peak conditions, test a system’s hardware and software configurations, and test an application’s ability to update.

  • Regression Testing - Regression testing consists of re-running functional and non-functional tests as a way to validate software performance after a change. Black Box Testing can be employed to verify whether a new version of software works as intended.

Black Box Testing Methods


There are many software testing techniques that fall under the Black Box Testing realm, each with their own specific test goals and advantages. Here are some of the main testing techniques:

  • Decision Table Testing - Decision table testing is a software testing technique that tests system behavior for different combinations of inputs. This technique helps testers learn the effects of various input variables.

  • State Transition Testing - State transition testing is a software testing technique used to determine the change in behavior/state of an application under various input conditions. For this type of testing, both positive and negative inputs are used to observe system behavior.

  • Equivalence Partitioning - Equivalence partitioning testing, also known as equivalence class partitioning, is a software testing technique that divides input variables into various classes of valid and invalid values based on test requirements. Test cases are then designed to cover each of the partition categories.

  • Boundary Value Analysis - Boundary value analysis testing is a software testing technique used to test and identify errors in the upper and lower limits of variable ranges. Variables at the upper and lower extremes of the input range typically result in more errors than variables at the center of the input range.

  • Error Guessing - Error guessing is a software testing technique that can be used when there is no specific methodology to identify errors. A test engineer uses their own experience and expertise to guess potential software issues.

What are the Pros and Cons of Black Box Testing?


While Black Box Testing has its many advantages, it is only one part of an overarching comprehensive test strategy and therefore comes with its drawbacks. It does not examine the internal workings of a system, which is where its counterpart, White Box Testing, comes into play. White Box Testing tests the internal code and structure of a system as opposed to looking at system behavior. Here are some of the primary pros and cons to Black Box Testing:


Pros

  • Tests are typically less complicated

  • Tests have lower chance of false positives

  • Testers do not need to be technical experts on the system under test

  • Tests are generally less time consuming

Cons

  • Tests can be difficult to automate

  • It can be hard to determine the root cause of failure

  • It is not practical to test all functionality

  • Tests do not examine internal software


Final Thoughts on Black Box Testing


Black Box Testing tests the external behavior and overall functionality of a system under test. It can be used for system testing or even acceptance testing, although it does not look at the internal workings of software. Its various software testing techniques each offer their own advantages, which can be sure to help your business verify systems in development.


 


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