Non-Functional Testing

As opposed to functional testing, the purpose of which is to verify that the actual product functions meet the functional requirements, as you might have guessed, the purpose of non-functional testing is to verify that the properties of the application match its non-functional requirements.

Non-functional testing means testing properties that are not related to the functionality of the system. These properties are determined by non-functional requirements that characterize the product from such sides as:

• Reliability (system response to unpredictable situations).
• Performance (system performance under different loads).
• Usability (investigation of the usability of the application from the user’s point of view).
• Scalability (requirements for horizontal or vertical scaling of the application).
• Security (security of user data).
• Portability (portability of the application to different platforms).
• And many others.

These properties of the system can be investigated using the following types of testing:

• Installation testing is verification of the successful installation of the application, its configuration, and removal. Reduces the risk of loss of user data, loss of application performance, etc.
• Usability testing characterizes the system in terms of the usability by the end user.
• Portability testing tests the performance of a software system under the conditions of various software configurations.
• Failover and Recovery Testing checks a software system for recovery from errors and failures. Evaluates the reaction of the application to errors.

As you can see, although non-functional testing does not check the system functions specified by the customer, it allows you to control more global properties: safety, performance, and reliability. These requirements characterize the quality of the software system, which leaves an impression on the user that affects how popular the developer company is.