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Black Box testing method

What is ‘Black box’? Black box (Opaque, Closed box, Function-centric) is a testing method that examines the functionality of an application without peering into its internal structures or workings. This method of testing can be applied virtually to every level of software testing: unit, integration, system and acceptance. It is sometimes referred to as specification-based testing. It is a powerful method, which is used to test the system against external factors responsible for possible failures. It focuses on the input, which goes in the software and the output, which this process produces. It is based on checking the system to validate against predefined requirements and emphasizes on the ‘software behavior’.

The Black box is commonly used for testing software usability, overall system functionality, getting a broader picture of the software, viewing the application from the user’s point of view and testing the whole system rather than different separate modules.

Black box testing evaluates all relevant subsystems, including UI/UX, web server or application server, database, dependencies, and integrated systems. It performs DAST (Dynamic Application Security Testing), which carries out tests in staging or production and provides feedback on compliance and security problems. 

The process of the testing is taken in several consecutive steps:

  • Understanding the requirement specifications of the application. An accurate and precise SRS document (Software Requirement Specification, which describes how the software should be developed) is required here.
  • Determining a set of valid inputs and test scenarios. The stage is aimed at saving time and getting good test coverage.
  • Preparing test cases to cover the maximum range of inputs.
  • Test case running. Outputs are generated to be validated with an expected outcome to spot pass or fail.
  • Marking the failed steps and sending the feedback to the development team.
  • Retesting the system with the help of various testing techniques.

 

Types of Black Box Testing

 

There are a number of types and approaches to Black box testing.They evaluate system security and functionality. The most known types are the following:

 

  • Functional testing. It is related to system functional requirements, and tests how well the system executes its functions. It helps to check the possibility of logging in by using correct user credentials only. It focuses on the most critical parts and aspects, such as Smoke testing or Sanity testing (a type of testing which shows the stability of the system in question. It consists of a minimum test set, which is run to test software functionalities), Integration testing (testing integration between the key components) or the system testing on the whole.
  • Non-functional testing. It is related to non-functional requirements and evaluates the readiness of the system by a number of criteria not covered by the functional testing. It helps to evaluate the usability of the software, its efficiency under expected and peak loads, as well as security vulnerabilities and common threats.
  • Regression testing. It is performed after implementing code fixes, upgrades and maintenance to check if the changes affected the existing functionality. It detects regression or degradation in capabilities from one version to the following ones, applied to both functional and non-functional aspects.
  • Vulnerability scanning. It allows checking the system’s vulnerability to attacks, discovering security holes and weaknesses to prevent real hacker attacks in future. During the process of testing automated tools like ZAP (OWASP Zed Attack Proxy) go along with manual vulnerability testing to cover the whole amount of possible issues.
  • Penetration testing. This type of testing simulates real attack scenarios, when the attackers try to get access to the data to compromise the system, and checks the software for abnormal responses or stack trace errors. In the majority of cases it is taken manually, but the automated part (with the help of tools like Powershell suite) can be added to cover it all.
  • Network topology discovery. It helps to study the network layout within the system (including the links between the elements and their interaction). It offers the identification of vulnerable elements to cut the future risks down.
  • Risk assessment. It is usually applied at the first stages of development and prevents security issues in SDLC (Software Development Life Cycle).

 

Among the approaches to Black box testing the main can be singled out:

 

  • Manual UI testing (to check and verify the user data and error messages);
  • Automated UI testing (to find errors and glitches);
  • Documentation testing (also a manual approach, to check purely the inputs and outputs). 

 

Black box testing techniques

 

There are several test case techniques, which include:

 

  • Boundary Value Analysis. It tests the software with extreme values of the test data and is used to identify flaws and errors, which appear due to the limits of the input data.
  • Equivalence partitioning. It checks inputs and outputs by means of dividing inputs into classes. It helps to reduce the redundancy of inputs.
  • State Transition Testing. It checks the software against the sequence of transitions or events and also for behavioral changes in this or that state while maintaining the same inputs.
  • Decision Table Testing. It includes a number of test cases in a decision table form, when every condition is checked for providing accurate outputs. It is useful in case of a large variety of input combinations and numerous possibilities.
  • Graph-Based Testing. It includes a number of test cases to check the relationship between links and input cases.
  • Error Guessing Technique. It helps to guess inputs and outputs to find the errors in the system and fix them later. A special type of error guessing is testing for known vulnerabilities.
  • Comparison testing. It uses two different versions of the same software to compare and validate the results.

 

Benefits of Black box testing

 

The Black box testing method has several benefits, which can be added to the ‘list of pros’ to choose it:

 

  • Not much technical knowledge is necessary and it is essential to see the user’s perspective.
  • The testing is performed after development.
  • It involves extensive coverage, helping detect issues potentially missed by testers.
  • Its methodology is highly flexible.


 

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