Functional Testing: Why It’s So Important & Where to Start?
Picture this: you bought new earphones that stopped working after the first usage. The device you paid for does not perform the required function. Frustration, disappointment, anger… And a bunch of other emotions, not to mention questions doubting the quality of the product and brand reliability.
The described situation is not rare in the IT world when solutions do not get the accurate dose of testing before the release or after some updates.
Considering that the primary goal of any product is to make a profit, we can hardly reach it without proper solution functioning. Here functional testing takes center stage. Thus, we decided to highlight one of the most important types of testing in this article.
Getting off the ground
Functional testing is used to check whether a solution or its components perform the assigned set of (business) functions and comply with predicted results. Any inconsistency between the actual and foreseen result is considered as a bug unless the case is described in specifications.
To test the software functionality, it’s necessary to have a precise list of the implemented functions and clearly understand the expected results of completing the prescribed tasks.
If there are no testing requirements provided by the customer, to form the list a QA engineer uses the software specifications, analyses functional requirements from both customer’s and end-users’ perspectives.
The next evolution step of this info after being explored and organized is the development of test cases (an ordered set of data required to verify each unit under test), supporting documentation vital for full-fledged testing.
Functional testing: when and how?
Functional testing can be done on different integration levels of system components, with the usage of various methods and tools.
Based on this, there are such peculiarities of and approaches to functional testing we’d like to cover:
- Levels of functional testing or when to test.
- Methods of functional testing or how to test.
- Types of functional testing or what to test.
- Boosting the process with automation testing.
Levels, methods and types of a functional testing
Levels of functional testing or when to test
There are different stages or levels of the software development life-cycle. Software testing can be conducted on unit, integration, system, or acceptance levels.
- Unit testing allows checking separate components of the system to verify whether they cope with the assigned tasks.
- During integration testing, the QA engineer focuses not on the functional blocks but on their connections, the degree of their interaction with each other, the connection order, fault tolerance, and the impact they have on the system functioning. The aim of checking a product on the integration level is to verify the components interaction and the correctness of the operation of functional subsystems.
- Speaking about the system level, here we check the entire system functioning and whether it fulfills the tasks the product was created for.
- Finally, acceptance testing is done to check software for acceptability, define its compliance with the business requirements, and readiness for delivery.
Methods of functional testing or how to test
As you may probably know, there various approaches to how to test a solution.
To be more specific, a QA engineer can choose from the black-box, white-box grey-box testing method.
Speaking about functional testing, the black-box testing method is used in most cases. Here, the QA engineer does not work with the program code, does not know what happens during the task run, what components and modules are involved in the process. In other words, the test engineer gets an opportunity to walk in the customer’s shoes, check the external work of the solution, and evaluate the system from the ordinary user’s perspective.
The main advantage of this method is that you’ll be able to release a product perfectly fitting the expectations of your target audience.
Using the white-box or clear-box testing method, a software tester gets access to the code of the solution under check and to the technologies used for its creation, verifying the internal structure of the program. The QA engineer should have the expertise and act on the developer level here.
In the context of functional testing, this approach allows detecting logical flaws in the code structure and spotting far more serious issues in the early stages of software development. Often, such testing is conducted by developers. It’s up to you to decide on whether to do it in-house or get a dedicated QA specialist and an outside perspective.
There are situations when it’s simply impossible to detect errors without understanding the operating concept of the program code from the UI side. The grey-box testing method is a kind of hybrid of white-box and black-box ones. It allows a tester to check the solution through the external interface, basing tests on knowledge of code parts.
As a result, we get the most effective verification of the product, detecting hard-reproducible, as well as non-obvious logical errors in the program code.
Types of functional testing or what to test
Smoke or build verification testing is conducted to cover the most important functionality of a system or its components to define the build stability and readiness for further planned testing.
This type of testing can be also performed at the final development stages to establish the product release or revert it for some improvements.
Smoke testing can be applied on integration, system, and acceptance levels providing the following advantages:
- Early detection of errors and problems.
- Integration issues disclosure.
- Confidence that made changes haven’t touched the functionality covered by functional testing.
Feature testing has a self-explanatory title and implies testing of the newly added or modified features. It can be done on all software testing levels using, in most cases, the black-box testing method with the following value-adds:
- Verification of different configurations and integrations of the software under test.
- In-depth check of all software elements.
- Elaboration of the feature metrics for further validation.
- Early issues detection, and, as a result, timely bug fixes.
Confirmation testing or retesting is performed after the issue fixing to make sure that the defect was corrected and won’t cause additional headaches reappearing in the future.
It can be done at all levels of testing, introducing such an obvious benefit as the solid assurance that the detected bug is neutralized.
The implementation of a new feature or enhancement of the existing one, configuration or design changes, code refactoring, or even a trivial bug fixing can open the Pandora box and trigger the appearance of new defects. It’s scary to imagine possible consequences. If you don’t want to deal with them in practice, it’s better to pay due attention to regression testing that can be both functional and non-functional.
This type of testing helps to confirm that implemented changes have not affected existing functionality.
Depending on the time, effort priorities and overall QA objectives, you can opt for full or partial regression testing. If you’d like to ensure the flawless functioning of the entire solution after made alterations, it makes sense to run the full set of test cases prepared for the product. If you consider that it’s more relevant to make general or version-specific prioritization based, for example, on critical or frequently used functionality, business impact or version based changes, and specific areas influenced by these changes, partial testing will be quite suitable here.
In most cases, this type of functional testing is applied on the system level, although it’s no less effective during unit, integration, or acceptance testing.
Automate or not to automate?
The functionality of any program comprises many tasks that should be regularly checked both during the software development process and after the release.
To increase software testing efficiency and exclude the so-called “human factor” in fulfilling humdrum activities, it’s better to use automation testing.
It may sound simple, but the reality is a bit different. There are cases when even all available diversity of tools for automating functional testing can’t help since not every check or test can be automated. Besides, not that easy to create a proper automated test. Be ready to spend a good deal of your time and effort on this task and analyze whether such a test is worth the trouble.
Summing up
Considering the outlined above complex of QA activities, it’s hardly possible to underestimate the importance of functional testing, including checks at the early stages of the software development life-cycle.
Functional testing is one of the fundamental tools for assessing the quality of a developed product.
And who wants to compromise on quality when dealing with the solution release to end-users and putting on the line reputation and money?
Do you always pay due attention to functional testing of your software?
