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Functional Testing vs Non-functional Testing | Quick Guide

Navdeep Singh Gill | 27 September 2022


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  • Functional Testing: This testing to verify the software's functionality mainly focuses on the functionality, not the actual code. This testing only validates the software's working, whether the software is working as expected or not, and doesn't test how the software is working.
  • Non-Functional Testing: Nonfunctional testing means you don't want to test the software's functionality. You need to focus on the execution speed, performance of software, and how much time it takes for the software to do a particular task. It means testing how the software is to work instead of testing what the software is doing.
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Why testing is important?

Importance of Functional Testing listed below:

  • Enhance the behavior: It enhances the application's behavior because it tests what the software does, what the software's functionality is, and is based on the business's requirements.
  • What the product does: It is what the software or products will do. It doesn't test how they only focus on the business requirements needed to fulfill those requirements.

Importance of Non-Functional Testing listed below:

  • Verifies non-functional features: Non-functional testing to those aspects left in Functional Testing, such as performance, usability, and reliability of the software.
  • How the product works: It is of how the product will work and its loading speed. The main goal of this testing is to test the performance of the software instead of testing what the software will do.
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What are the various types?

The types of Functional Testing below mentioned

  • Unit testing: Testing each individual's unit of the software. The unit is the single testable part of the software.
  • Smoke testing: Used to determine whether the build is testable or not, which does not require any design test case for testing the software.
  • Integration Testing: Used to test the interfaces between the software modules, performed after the unit testing. Test the communication between the tested modules of the software.
  • Regression testing: Used to determine whether the software is still working fine after bug resolution or doing some changes in the code to solve the bugs. In which test cases are re-executed to retest the things.
  • User Acceptance: Used to test the end-to-end flow of the requirements of the software, which is performed at the end of the final stage.

The types of Non-Functional Testing described below:

  • Performance Testing: Test the software performance or response time by applying load on software. It performs after performing it properly.
  • Volume Testing: Used to test the software's performance by applying the software's load in a certain amount, not overload. A certain amount means either load is less than this or equal to the actual load of the software.
  • Usability Testing: Used to test the software from an end-user point of view whether the software is working as accepted. This testing determines whether the software is easy to use or not for the target user.
  • Stress Testing: Used to test the performance of the software by applying the load on the software in a more significant amount than the actual amount of the software.
  • Compliance Testing: Used to test whether the system developed meets the organization's prescribed standards or not. This testing determines how a system under test confirms it meets the independence requirements of a particular standard, standards like IEEE, W3C, or ETSI.
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Difference between Functional and Non-Functional Testing?

Functional Testing Non-Functional Testing
Customer requirements: It's based on the customer requirements which helps enhance the application's behavior. Customer expectations: It's based on the customer's expectations, which helps improve the software's performance.
Used to: This testing is used to identify what the software does, not how it works. This means it tests the functionality of the software. Used to: This testing is used to identify how the software will do it to test the performance of the software.
Focus on: Expected and actual results. Focus on: Performance, speed, and response.

What are the best testing tools?

Best tools for functional testing are:

  • Selenium: Selenium is not just a tool. It's a set of tools such as Selenium IDE, Selenium RC, Selenium WebDriver, and Selenium Grid. This tool supports various languages like JavaScript (Node. JS), Python, Ruby, Java, Kotlin (programming language), and C#. It's an open-source automation set of tools. It doesn't support any desktop applications.
  • Test Complete: Test Complete will cover all tests, like regression and parallel tests. Testers have used this tool when they want to speed up testing cycles. With the complete test tool, the tester can write automated test cases for Web, Android, and iOS applications.

Best tools for non-functional testing are:

  • JMeter: JMeter tool is used to measure the performance of software services and products and analyze them. Used to perform load testing and functional testing of web applications. How it performs the testing:
    Create the testing request for testing, receive the response from the server after sending the request to the server, analyze/visualize the result, and then generate the test results in various formats, such as JSON XML for the tester. This tester analyzes the result.
  • Load Complete: This load testing tool runs automated load tests for web servers and services after creating the test. It monitors various server metrics, such as CPU usage during the test run. It supports all types of web servers and client web applications (browsers)
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In conclusion, functional and non-functional testing both play a significant role in testing because these testing functionality and performance are tested properly on the software. There are lots of tools for both testing, such as selenium, JMeter, and load completely. All the tools are handy. The goal of both tests is different: one is testing functionality, and another is testing the software's speed and performance.