Functional Testing (also known as Black-box testing) is defined as the testing of a mobile application or a web application in which a tester does not know the design of it or how it works.
He uses it and reports irregularities occurring in its functioning.
The black box metaphor does not appear here without reason.
A mobile or web application that undergoes Functional Testing is treated like the proverbial black box.
It is the “outside” part of it (e.g., the interface) that is tested, not its “inside” (e.g., the source code).
The opposite of Black-box testing is White-box testing, in which the “inside,” meaning application code, is being tested. In particular, it is tested for its structure and logic of operation.
Functional Testing of an application allows you to check the following:
- proper operation of a function
- consistency and completeness of functional and non-functional requirements
- user interface
- client-server communication.
In addition, many problems involving requirements are apparent at the Functional Testing design stage, long before testing is performed on a finished software.
Performing Functional Testing also makes it possible to understand how the system works under certain conditions.
What is equally important is the collaborative testing of software by business analysts, programmers, and customers that results in a consistent and shared vision of how an application should work.
Testing is an effective and recommended tool used equally to validate and verify requirements.
Who are the testers performing Functional Testing?
Usually, testers are not programmers, and their programming knowledge and experience are similar to that of the average application user. The lack of knowledge and experience of testers is intentional and desirable.
It is about obtaining a specific perspective of a "non-technical" person.
Testers, of course, are told what the application is for, but they are not familiar with how it works or performs calculations.
Functional Testing is about checking the performance of a web application or mobile app from the perspective of a person who will be its potential user.
A user who expects it to operate intuitively, simply, and similarly to the operation of analogous applications.
And, of course, without errors. An app that allows achieving goals and tasks.
An application undergoing Functional Testing is primarily intended to work according to the expectations of its users, not its developers, who evaluate it to meet technical requirements. Functional Testing verifies that an application works according to specified requirements.
What are the purposes of Functional Testing?
The primary purpose of Functional Testing is to check how the application works from a functional point of view.
To put it in slightly more technical terms, the purpose of Functional Testing is to check how functionalities contained in the System Requirements Specification are implemented.
The method is all about answering questions – How does the system behave? How does the user perceive it?
How does it perform tasks? How does it help to achieve objectives?
An entire application, or parts of it, can be the subject of testing. Testing also encompasses how the application works with other external systems.
Like any testing, Functional Testing is focused on detecting and analyzing emerging bugs or imperfections in application performance.
They are used not only for diagnostics but also for determining the cause of an error. Although, of course, we don't mean causes in the technical sense.
However, the testing of a mobile or web application is not haphazard but is usually carried out based on test scenarios used to diagnose individual functionalities.
A test scenario is a collection of actions that an application tester should perform.
Looking at Functional Testing from yet another perspective, it can be said that its purpose is to see how and to what extent the application can meet business objectives.
Functional Testing is focused on the following:
- testing the most important functions of the application
- checking the basic usability of the application, in particular, whether moving from one screen to another is trouble-free
- determining the application availability level
- determining error conditions.
When can Functionality Testing be performed?
It may seem that only the finished, completed version of a mobile or web application can be tested. However, this is not a necessary condition.
Both finished products and those just in the production process can be tested. These tests can be performed at any stage of the work. A very popular method is to test the application at successive crucial phases of its development.
Regular and scheduled testing helps avoid many errors and costs involved in fixing them.
They differ from tests performed on a completed and implemented application.
The latter is more focused on testing the consistency of the application, its completeness, and the security it provides to users.
Tests performed after the completion of a given stage of work are more geared toward verifying the proper operation of a given functionality and how it helps achieve business objectives.
Functional Testing Types
The most fundamental distinction of software tests is the division by tester criteria. It could be a human or testing program.
In the first case, we are talking about manual tests; in the second, we mean automatic tests.
Manual tests, inevitably, are more demanding in terms of:
- organization of testing sessions
- credibility, reliability, and correctness.
The risk of mistakes, of not following a methodology, or a test scenario, is higher wherever the tester is a human being.
However, manual tests also have a huge advantage; they allow you to test applications from a purely human perspective.
They provide insight into automatically performed actions that can lead to desired or undesired results (application works as expected vs. application does not work as expected).
They allow you to see the very human dimension of human–software interaction.
And this is of colossal importance in terms of offering a satisfying User Experience.
Manual Functional Testing usually focuses on the performance of the application interface. It provides answers to the question of whether the function is working properly, as well as whether it is working satisfactorily.
This very important feedback is something that automated tests, unfortunately, cannot guarantee. That is why they are less useful in UX research.
Automated tests are performed based on a test script and allow verification of the application's performance in multiple dimensions.
Their main advantage is the execution speed, much higher reliability, and less susceptibility to errors.
They are especially recommended when expanding the application, adding new features, or checking the application's behavior after the implementation of a repair or optimization work.
Benefits of testing web and mobile applications
Why perform Functional Testing? The main argument in favor of application testing is, of course, the cost that errors generate.
And as a rule, the cost of fixing errors increases with the complexity of the application. It is lowest at the early stages of its production and very high when the application is already functioning on the market.
Unfortunately, fixing bugs in already implemented applications that are functioning on the market has the disadvantage of being a source of errors.
Improving the performance of a function can influence the operation of other functions, which complicates the work and increases the repair cost.
That is why function testing should take place while the application is still in production. This reduces the risk of errors, conflicts, or contradictions in the operation logic.
Repair work is also much easier to perform under such conditions.
When we say cost, we mean not only financial cost but also loss of credibility, trust, and deterioration of the application's reputation. In conclusion, the image of the brand suffers.
And losses in this dimension translate into financial losses. Rebuilding a reputation is a difficult and also costly task in the world of digital products.
Testing is also necessary for a more obvious reason. Creating a flawless application is very difficult. The source of the error can sometimes be a mistake, an oversight, or a wrong assumption.
Not only programmers but all stakeholders involved in developing the application are susceptible to making mistakes.
Another obvious fact is also worth mentioning.
From the point of view of a mobile or web app user, a buggy application is useless, risky, and untrustworthy.
Eliminating errors is essential if the application is to succeed on the market.
It is safe to say that a buggy application is as attractive to a user as a car with no wheels is to a racing driver.
Best practices for Functional Testing
Testing can be done in at least several ways, depending on your needs and the goals you want to achieve.
Functional Testing of web or mobile applications may consist of the following:
- verifying the functions of the application according to the specifications
- performing specific tasks in the application
- spontaneous use of the application without a clear purpose or scenario.