•  If system is not functioning properly, its a functional defect.
• If system is not performing well, its a performance defect.
• If system is not usable, its a usability defect
• If system is not secure, its a security defect
• and so on..

Identify these different defects require different skill set, different techniques and different type of test cases. Testing is divided into different types to reflect, what kind of defects can be uncovered by those activities. This division also helps management in managing these activities effectively. Also, it is very rare to have someone with skills in all the types of testing and this division helps in getting proper resources for team.

Hope you understand importance of this categorization and also how important it is to have understanding of different types. This understanding will enable you to spot more defects which in turn will improve quality and make you more effective software tester.

There are many ways in which software testing can be categorized. Some of them are described as follows: 

Categorization of testing based on the knowledge of system

• Black Box Testing
• White Box Testing
• Gray Box Testing

• Unit Testing
• Integration Testing
• System Testing
• User Acceptance Testing

• Functional Testing

In functional testing, the focus of testing activities is on functional aspects of the system. In functional testing, test cases are written to check the expected output. Functional testing is normally performed in all the test phases from unit to system testing.

The following types of test activities are normally performed under Functional Testing


• Installation Testing
• Regression Testing
• Upgrade and backward compatibility testing
• Accessibility testing
• Internationalization and localization testing
• API Testing


• Non-Functional Testing

In non-functional testing, the focus of the testing activities is on non functional aspects of the system. Non functional testing is normally carried out during the System Testing phase only. The focus of non functional testing is on the behavior and user experience of the system.


• Performance, Load and Stress Testing
• Usability Testing
• Security testing
• more to come..

Testing can also be categorized based on how it is executed. Execution  could be in the form of verification or static analysis or it could be validation or dynamic analysis. Verification and validation can be categorized further according to how it is done.

• Verification

In very simple terms, verification is the human examination or review of the work product. There are many forms of verification which ranges from informal verification to formal verification. Verification can be used for various phases in SDLC and can be in the form of formal inspection, walkthrough or buddy-checking.

• Validation

  Validation or dynamic analysis is the most frequent activity that as a tester you perform. Whether you are doing black box testing, non functional testing or any type of testing, chances are that you are performing validation or dynamic analyses. Validation or dynamic analyses is associated with the execution, and could be related to the execution of test cases or testing in general. There are many ways in which testing can be executed, for example

  • Manual Scripted Testing
  • Exploratory Testing
  • Automated Testing
  • Model Based Testing
  • many more..