Functional and non-functional tests in software testing

Use cases, test types, and automation options for functional and non-function software tests

Key Takeaways

  • Software testing falls into two buckets: functional and non-functional.  Both types of tests are highly valuable for successful product development.

  • A good way to distinguish between the two types of testing is that functional testing assesses what a system does while non-functional testing assesses how well a system performs, based on what it’s supposed to do.

  • Functional testing focuses on usability, accessibility, and functionality (of course). Unit tests, integration tests, and acceptance tests are a few examples of functional testing.

  • Non-functional testing is designed to test for security, reliability, and efficiency.

Software testing falls into two buckets: functional and non-functional.  Both types of tests are highly valuable for successful product development. Understanding their use cases can help you develop a stronger testing strategy for higher quality products and faster delivery times.

The role of functional and non-function testing in software development

Functional testing tests the behavior of an app. The purpose of functional tests is to test every function of the app, by providing the appropriate input and then verifying the output against the Functional requirements.

Meanwhile, non-functional testing tests the readiness of a system and different non-functional software requirements related to usability. The purpose of non-functional tests is to improve the usability and efficiency of an app, as well as maintenance.

A good way to distinguish between the two types of testing is that functional testing assesses what a system does while non-functional testing assesses how well a system performs, based on what it’s supposed to do.

Both functional testing and non-functional testing are critical components to the software testing life cycle. These automated tests help DevOps teams in three key ways. First, testing helps to find or prevent bugs, which improves the end quality of a product. Functional and non-functional tests also shrink development costs by highlighting issues earlier on in the development cycle, before they progress and become major (and expensive) problems to clean up after the fact. Third, automated software testing also ultimately helps devs to release the best, most accurate, high-performing product.

Functional software testing analyzes software performance.

Functional software testing tests if the features of an app perform per the software requirements. Functional software testing is black box testing, and does not test source code. Functional tests focus on testing for:

FunctionalityDoes the main function work?
UsabilityHow easily can a user navigate the app?
AccessibilityHow easily can a user access the app?
Error ConditionsAre error messages suitably displayed?

Overall, functional testing helps determine how well the features of a system work. Within functional testing, there are 5 main types of functional tests including: unit tests, integration tests, integration tests, system tests, and acceptance tests. 

# 1 Unit tests

Unit tests are the smallest types of software tests as they only test a single unit of code isolated from the system. The purpose of unit testing is to validate if a unit of the software code performs as needed and to verify the correctness of a piece of code. 

# 2 Integration tests

Integration tests assess the compliance of a system, feature, or component with specified functional requirements. The big goal of integration tests is to ensure that all of the key components work together.

# 3 Interface tests

The communication between different interfaces, including data exchange, data transfer, messages, calls, or commands.

# 4 System tests 

Evaluate the overall compliance of the system, by integrating all of the components together, to verify if the system performs as expected. The purpose of a system test is to test the end-to-end system specifications. 

# 5 Acceptance tests 

Essentially show testers how a product functions. Acceptance tests display if and how an app meets the final user approval. Acceptance testing comes in many flavors, including beta testing, field testing, and end-user testing.

Non-functional software testing for usability assessment.

Non-functional software testing assesses the specifications that impact a user’s experience, but may not directly influence if and how an app performs. Non-functional tests focus on testing for:

SecurityHow safe is the app from internal and external threats?
ReliabilityHow dependable is the app?
UsabilityHow easily can a user learn, operate, and interact with the app?
EfficiencyHow does the app handle capacity, quantity, and response time?
FlexibilityHow does the app transfer from its current environment?
ScalabilityCan the app expand processing capacity to meet more demands?

Overall, non-functional testing evaluates the usability of an app. There are key non-functional software tests: performance tests (including load, stress, and stability tests), security tests, usability tests, compatibility tests, and regression tests.

# 1 Performance tests

Performance tests evaluate how an app will perform under different workloads and show the stability, speed, and responsiveness under different conditions. The goals of performance testing are to asses the speed, efficiency, and power of app when it comes to output, processing, data transfer, network bandwidth, max users, memory, workload, and response times. There are 3 major kind of performance tests, including:

  • Load tests determine how a system behaves under both normal and peak load conditions. In a load test, the demand is constantly ticked up on the system, in order to discover the system’s max threshold.

  • Stress tests evaluate stability and reliability, with test scenarios performed under heavy load conditions. Stress testing 

  • Stability tests test the efficiency of an app’s ability to function over the long haul, and uncover if and when an app might fail, under normal circumstances. 

# 2 Security tests

Security tests determine if an app will be protected from potential internal and external risks and threats. The aim of security tests are to identify the weaknesses and flaws that could lead to data loss, revenue loss, or hacking. Security tests are an invaluable piece of the testing life cycle and critical to ensuring you and your end users are protected.

# 3 Usability tests 

Exactly what they sound like, usability tests require humans to interact with an app, so that emotions, reactions, and behaviors to the product can be observed.  Meanwhile, cross-browser testing is very similar, and evaluates if an app works for users on varying browsers and devices.

# 4 Compatibility tests 

Compatibility tests are designed to explore if a system performs as needed on different browsers, databases, operating systems, networks, and devices. Compatibility is super important to not only users, but from a business perspective as well. For example, an app that’s compatible with every browser will be more loved by users than a similar app that only works on Google Chrome.

# 5 Regression tests 

Regression testing is not part of functional testing, but it is a form of re-testing previous functional tests after release. Regression tests ensure existing functions have not been negatively impacted by a new code change or updates. Regression tests are performed after a code change, or a bug is discovered, to make sure existing code is not harmed. Regression testing must be continually performed throughout the development and testing cycle, which often makes it a significant bottleneck, dreaded by devs.

Automate functional and non-functional test case selection to shorten test suite runtimes.

It’s pretty clear that functional testing and non-functional testing are critical to the mission success of an app. However, software testing is often the largest hurdle for developers, as massive test suites and slow run times delay development. That’s where Launchable comes in.

Launchable’s Predictive Test Selection dynamically reorders your tests, by ranking tests on importance, based on code changes. With this information, only the tests with the highest likelihood of failing (based on your code and test metadata) and the highest value tests for a specific change are automatically run, which drastically shrinks the size of your test suite and testing cycle times. 

Launchable’s Test Suite Insights also provides invaluable metrics that can help you track the health of your test suite and end test suite entropy. Launchable’s Test Suite Insights offers data on 4 key metrics, including:

  • Flaky test insights - pinpoints the top flaky tests

  • Test session duration insights - shows increases in test session times 

  • Test session frequency insights -  highlights tests are being run less often, have higher cycle times, or diminishing quality.

  • Test session failure ration insights - finds the tests failing often and checks on stability

With Launchable, functional and non-functional software testing becomes faster than ever, while ensuring your team has the highest confidence errors and flaws will always be found.

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