Best Practices for Functional Testing | Global App Testing

What is functional testing? What are the functional software testing best practices? Our guide discusses the differences between non-functional and functional software practices, functional testing best practices, and how to test software functionality. 



Table of contents

  1. What is functional testing in software testing?
  2. How to test software functionality
  3. Non-functional vs functional testing
  4. 5 Functional testing best practices
  5. Make functional testing part of your QA strategy

What is functional testing in software testing?

Functional testing is a type of black-box testing. It answers the fundamental questions “does this actually work?” and “can the user do what we expected?” This method of software testing tests the functional requirements of an app, verifying whether the software works as per customer needs. Functional testing is not concerned with how processing occurs, but rather, with what the results of processing should be.

Functional testing checks:

  • The main functions of a piece of software or a web application. Quite simply: do the features work as intended?
  • How easy it is to access - can the end-user interact with everything they need to?
  • Usability. The end-user should be able to make use of it without any difficulties.
  • What happens when errors occur - are there appropriate messages, and a way of logging them?

How to test software functionality

There are 6 steps in the functional testing process: 

  1. Identify and clarify the functions that you expect the software or web application to perform
  2. Create input data based on these functional specifications
  3. Determine the output based on these functional specifications
  4. Write and execute test cases to gather test data (these can be manual or automated tests)
  5. Compare the results of actual and expected output
  6. Make changes if the results don’t match the end user’s needs
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Non-functional vs functional testing

So what is the difference between non-functional software testing and functional testing? The answer is relatively simple: non-functional testing is concerned with how, and function testing is concerned with what. Functional testing verifies what the system should do, and non-functional testing tests how well the system works. Functional testing is carried out to verify software actions, and non-functional testing validates the performance of the software.

Another comparison you might see when discussing this is black box testing vs white box testing. Black box testing looks at the functionality of the software without looking at the internal structures. White box testing looks at these internal structures.

Functional vs non-functional testing comparison.

Types of functional testing:

  • Unit testing
  • Functions
  • Accessibility
  • Smoke testing
  • Integration testing 

Many functional tests will be designed around given requirement specifications - meeting business requirements is a vital step in designing any application. For instance, a requirement for an ecommerce website is the ability to buy goods.

A practical example of this is: when a customer checks out of a shopping basket, they should be sent to a secure payment page, then to bank security verification and then they should receive a confirmation email. Functional testing verifies that each of these steps works.

Types of non-functional testing:

  • Performance testing
  • Load testing
  • Reliability
  • The readiness of a system
  • Usability testing

A practical example would be: checking how many people can simultaneously check out of a shopping basket.

Not every type of software test falls neatly into these two categories, however - for instance, regression testing could be considered both depending on how the tests are run.

5 Functional testing best practices

  1. Use exploratory testing
    Exploratory testing is a particular testing method that involves a lot of freedom on the testers part. In exploratory testing, the testers investigate an app to try and identify potential bugs. This method is relatively unstructured, and testers have the freedom to run tests how and when they see fit. This simultaneous process of test design and test execution is hugely beneficial for functional testing.

    Testers explore your software to ensure that it performs the tasks it was designed for, discovering any potential bugs in functional aspects of your app. Since it’s focused on how the app works, rather than how it’s put together, these testers don’t need any particular background in a language like Python or Java - just a familiarity with QA.

    Testers are tasked with investigating an app in its entirety, in real-world scenarios with real devices. By testing on-demand with minimal preparation required, you can receive fast and valuable direction on the bugs in your app or software product.

    Partnering with a company like Global App Testing can improve your quality assurance process by providing you with 15-20 professional testers. These testers come armed with the best practices to locate reproducible bugs within your app. Your exploratory test results will come back to you in 24-48 hours.

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  2. Automate some (but not all!) of the process

    Test automation can save time and money. If you are repeatedly testing a specific function, it does not make sense to waste valuable resources on either your DevOps or QA team physically testing the same function again and again. By writing test cases for automation, you can run thousands of tests at once, verifying that the specific feature you are targeting works as expected.
    But you cannot automate all functional testing. Exploratory testing, for example, cannot be automated in its entirety. That’s because it requires the creativity of testers to initially explore the app and decide which parts of it to test. System testing and user acceptance testing also require manual efforts. Luckily, there are many functional testing tools available to make it easier.

    To create a high-quality product, you need to implement a blend of manual and automated testing. Creating a Requirement Traceability Matrix (RTM) is one way you can ensure all business requirements are tested, whether by automation tools or your testing team. By making this combination part of your QA strategy, you will ensure that you discover more software bugs and cover more testing bases.

  3. Use well-planned test case execution

    Test execution is the process of testing specific workflows in your app. This is crucial to functional testing. By using test execution, your testers can work their way through particular functions for your mobile or web app, ensuring that they work as they should within the pre-planned workflow.

    Let’s say you write a test case for your ecommerce app. You want to ensure that users can search for ‘red trainers’, click on a specific pair, add to their shopping bag and checkout. Within each of these steps, testers will be testing specific functions like the search bar, card payment, and shopping bag, to see if they get the expected results. They can then report on the application’s conformance to the requirement specifications, and the development team can make appropriate changes.

    By planning test execution rigorously, you can ensure that the test case covers all functionalities.

  4. Test early and test often

    You need to catch issues with functions on your app or website early in the software development lifecycle (SDLC) to prevent them from having a real impact on your company. By testing functionality early, you can save your company money by identifying design issues with specific functions before they become too costly. 

    For example, if the checkout function of your shopping app is full of bugs, you will see a direct effect on revenue. Equally, if the ‘sign up’ functionality on your website isn’t working correctly, you will inevitably suffer a loss of sign-ups. Running functional tests early dramatically reduces the chance of this happening.

    You don’t want to wait until the last stages, or the UAT (user acceptance testing) phase to find out what’s wrong! Implement testing techniques like unit testing in the design and development stages of your product to avoid functionality issues further down the line.

  5. Partner with a professional team

    If you partner with a company like Global App Testing, you can shift the time spent on functional testing to a crowd of testers, so you have more time to focus on test strategy and analysis. This will free up internal resources so that you can focus on developing new features and designing app updates.

    For exploratory testing, Global App Testing uses a team of 15–20 experienced testers per test, armed with the best practices to discover potential bugs in your software.

Make functional testing part of your QA strategy

Functional testing is essential, and when executed correctly, it can reduce the number of software bugs you encounter, and improve the experience for your customers.

As discussed, functional testing is best undertaken through a combination of manual and automation testing. The automation means that simple, repetitive tasks are thoroughly checked, whilst manual testing is great for finding those odd bugs caused by user interaction.

Whether you’re designing software, web apps, or an API, it’s important that it works. Functional testing is the key to understanding whether it does - and if it doesn’t, how to fix it.

Why not speak to one of our team to learn more about how Global App Testing can help with your functional testing needs today.

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