What is functional testing in software testing?
Functional testing 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.
How to test software functionality
There are 6 steps in the functional testing process:
- Identify and clarify the functions that you expect the software to perform
- Create input data based on these functional specifications
- Determine the output based on these functional specifications
- Write and execute test cases
- Compare the results of actual and expected output
- Make changes if the results don’t match a customer’s needs
Non-functional software testing types 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.
Non-functional testing checks:
- Performance
- Readability
- Reliability
- The readiness of a system
- For example, checking how many people can simultaneously check out of a shopping basket
Functional testing checks:
- Usability
- Functions
- Accessibility
- For example, 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.
5 Functional testing best practices
1. Use exploratory testing
In exploratory testing, 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. This is a valuable technique in exploratory testing, as it allows testers to investigate 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. Partnering with a company like Global App Testing can provide you with 15-20 professional testers 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.
2. Automate some (but not all!) of the process
Automation can save time and money. If you are repeatedly testing a specific function, it does not make sense to waste valuable resources on many testers 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.
To create a quality product, you need to implement a blend of manual and automated testing. By making this careful combination part of your QA strategy, you will ensure that you discover more software bugs and cover more testing bases. Find out more about automation vs humans in our article here.
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 e-commerce app. You want to ensure that users can search for ‘red trainers’, click on a specific pair, add to shopping bag and checkout. Within each of these steps, testers will be testing specific functions to see if they work as expected like the search bar, card payment, and shopping bag functions.
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 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. 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. In this guide, we have shown the value of functional testing in:
- Discovering bugs that may affect your users
- Ensuring the functionality of your software works correctly
- Saving your company time and money
