When working on a piece of software, testing is one of the most crucial elements of the production process. It allows the development team to find out what works and what doesn’t, and doing it in a proper, standardized manner will give your entire work crew a better sense of communication. With proper testing practices, you can ensure your product stays at its highest quality, minimizing the number of bugs and flaws the users may experience and speeding up the development process.

Functional testing is one of the general software testing categories, meant to verify the functionality of an app or a website. Testing isn’t something done only at the very end of development – in fact, in the early planning stages of the project, you should create a list of functional specifications. Simply put, make a list of what your software is supposed to accomplish.

Implementing a proper functional testing phase can be very beneficial to your development process. How exactly to implement it properly? Let’s see what functional testing is all about with some examples to make it easier to understand.


Who can perform functional testing?

Since functional testing is a black-box software testing technique, the tester doesn’t need any knowledge about the inner workings of your software. In fact, the tester doesn’t even need to know anything about programming – functional testing is all about user experience, so the tester shouldn’t need any more knowledge than an average user is privy to. In fact, functional tests are most effective when performed by someone without deeper knowledge of the system they are testing.

With functional testing, you can easily check the main functionality of your software, confirming whether all required features work as intended. It also gives you the ability to see how accessible the app is to standard users – as a developer and (most probably) a programming specialist, your knowledge allows you to instinctively use an app or a system in a way that a standard user wouldn’t be able to. Functional testing lets you see exactly how usable the software is for such users, letting you see whether the end-user can use the software comfortably and what exactly happens when an error occurs.

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What are the types of Functional Testing?

Since functional testing is more of a category of software tests than an individual testing methodology, there are a variety of types of functional tests. The most common types of functional testing are:

  • Sanity Testing
  • Smoke Testing
  • Integration Testing
  • System Testing
  • Component Testing
  • Unit Testing
  • User Acceptance Testing

Sanity Testing is performed whenever your software gets updated with new bug fixes and changes. It verifies all of the newly introduced functionalities, making sure they work as intended. Most often, sanity testing is considered as a type of regression testing, and many programmers get it confused with smoke testing – let’s see why.

Smoke Testing is very similar to sanity testing, but there is a definitive difference. Smoke testing is performed on initial builds of the software, verifying that basic functionality works. This type of testing isn’t exhaustive – and it isn’t supposed to be. It aims to go over only the most fundamental components of your software. 

Integration Testing gives you the ability to confirm whether individual functionalities and components of your software perform well together. It is performed after all of the individual modules have been confirmed to work without flaws and is one of the most popular types of functional testing. Integration testing can be easily automated, and often is, making it a simple step in the QA process.

Once you are sure that all functionalities operate fine individually and when integrated together, it’s time for System Testing. System testing is performed not to confirm whether something works, but whether your software complies with specific requirements. These are most often requirements given to you by your client, and system testing gives you the ability to easily measure how well you have achieved what your client wanted of you.

Component Testing is performed before integration testing to verify the individual performance of every component of your software. Keep in mind that these components aren’t simply consisting of a single functionality. For example, a component test for the login component of a website might include testing the visibility of the UI, page loading, SQL performance, and end-user experience.Finally, Unit Testing is a very thorough test that directly examines the code of your software’s components to make sure it is doing exactly what it is supposed to do. Unit testing can provide valuable documentation of your code development as you progress with the software’s production, which can be extremely useful to communicate between teams and speed up the work. Without unit testing, failed tests can be much harder to explain, and finding error sources will take much more time.

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Conclusion – how to understand Functional Testing?

Since there are so many types of functional testing tests, it’s impossible to provide an example that would fit all of them. Instead, we want to demonstrate to you first a simple functional testing framework. In its simplest form, functional testing can be said to have three steps.

  1. Prepare input values and categorize them into test cases
  2. Verify your test cases
  3. Compare the results to the software requirements and expected results

However, functional tests can have varying degrees of complexity. Let’s consider the example of a login functionality test. Unit testing would require dozens of test cases and many scenarios, including every part of the login process. In turn, a simple smoke test would require much fewer cases, only verifying the functionalities critical for the end-user to log in.

As you can see, functional testing is a fascinating and very comprehensive subject, with many software testing types that will surely be useful to any software developer. With proper testing practices, your software can achieve better quality much faster, fostering communication and cooperation between different teams working on the same project.

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