How To Proceed With Functional Testing? A Detailed Guide

Functional Testing Guide

Functional testing is one of the most important fundamental steps to ensure that all the elements of the application are justifying their functional specifications and expectations. The most common strategy of performing these tests is providing some predetermined sets of input and observing if the outputs are coming accordingly. Those observations can help you analyze if the application would serve the users’ purposes that they are developed for.

In most of our articles, we have discussed how important software testing is and how efficient it is to automate them using advanced low-code testing tools like Preflight. Testing tech products are often considered much more important than focusing on developing numerous features because a successful business should always prioritize maintaining efficiency, consistency, and positive progress that will eventually lead their users to trust in their products. Offering numerous attractive features that often break and fail to serve users’ purposes is not going to stay as a long-term foundation.

However, here we are going to discuss more of the operational sides of functional testing so that you can figure out which strategy will get you the best results.

What Is Functional Testing?

Functional testing is the method of checking if any tech product as well as all of its components are functioning as they should. You have already got to know a lot about it in the article “What Is Functional Testing?” However, if we just mention the key aspects, this form of testing consists of a few different types of testing techniques that have almost the same goal of letting the app’s components perform their operations on some predetermined inputs and observing if they are producing the outputs that they are expected to. Now, we are going to focus on how you should perform them efficiently to get the best results.

How To Perform Functional Testing?

Functional tests are performed at a very basic level of the entire process and that’s what makes them very crucial to make the decisions for the further phases. So, let’s take an in-depth look at the step-by-step approach to effectively performing functional tests.

1. Understanding The Users’ Needs & Pain Points

This is an absolutely unavoidable and highly important step for every business. You are developing products to serve its potential users and its features must solve the problems that they were struggling with.

Sounds complicated?

Well, let us simplify it. The idea of building a tech product mostly comes from observing an issue that a set of people are facing. Various surveys are conducted and stats are collected to make the plans before starting to build the app. Similarly, when you are performing the functional tests, you must have an idea about what the users need from the app and what pain points they are trying to get rid of using it. Hence, the first step of the functional testing process always involves collecting those details.

2. Creating A Great Test Plan

Almost nothing can be done properly without strategic planning. So, it is almost impossible to execute complex test suites without making proper plans for them. Users can proceed through the various components of your app in numerous ways and it is impossible for the testing team to predict all their actions. Now, based on different user actions, the app can function differently, and run into different consequences. That’s why it is highly important to consider all the possible scenarios and create tests for them accordingly. This will help you get a clearer idea of the potential challenges that you may face during the tests, and to make effective counter strategies for them. Effective test plans lead you to easily detect the bugs in the functional testing level so that you can make decisions about conveying them to the development team for debugging and quality improvement. Test plans are also useful for their capability of letting you decide the tools to be used, roles & responsibilities for different team members, the scope of work, timeline for deliverables, workflows, etc.

3. Writing A Test Case

Now, as you have your test plans ready, it’s time to move ahead with actually writing the tests. As we mentioned in our article “What Is Functional Testing?”, the ultimate results of these tests should be either “pass” or “fail”. So, for that, you need to have a predetermined set of ideal results ready, and then analyze the actual results to categorize them into passed or failed tests. Hence, you must keep that factor in mind while writing your tests and then be ready to maintain spreadsheets of the passed or failed tests.

4. Executing The Test Cases and Analyzing The Results

After writing the test cases, now you must go on with executing them according to the test plans you prepared earlier. You must pay utmost attention to comparing the actual outputs with the expected outputs for the predetermined inputs. If there is any difference in those two sets of outputs, make sure to document them in the order of most to least important. Maintaining proper records for the test results of each test case is essential as those records will let you know if the new code changes are affecting the existing codebase.

5. Performing Regression Tests

This is somewhat of an occasional step. As you have already seen in our regression testing article, these tests are performed to ensure that the new changes to the code are not harming the existing code. Hence, if in the result analysis phase mentioned above, it is found that the new code changes that are being deployed are causing new issues in the application, regression tests should be performed. These are also super-important types of functional tests, and you can learn more about how to perform them from the article “How To Perform Regression Testing? The Complete Guide”.

Functional Testing Techniques

To perform the functional tests with maximum efficiency in different use case scenarios, different effective techniques are followed. We have jotted them down below.

1. End-user Based/System Tests

The phenomenon of these tests is testing the combinations of all the functionalities that the users use to perform their tasks. For example, posting an image on Facebook will need to perform the following tasks -

  • Logging on to
  • Entering your User ID and Password.
  • Clicking the “Log in” button.
  • Clicking the “Upload Photos/Videos” button.
  • Selecting the image.
  • Entering any caption or description if you want.
  • Clicking the upload button.

Hence, to ensure that all the UI components involved in the task are working properly, you must test the entire combination of the components.

2. Equivalence Tests

In this functional testing technique, the test data is divided into multiple partitions, and the data in each partition is expected to respond in the same way. That means if the condition that is being tested works in one partition, it must work in the other partitions too. For example, in any form, there must be a specific character limit of 10 digits for an Indian mobile number in an input field, and it must accept numbers only. So, if someone tries to enter any type of data other than numbers, the input field should not allow that. And, the same should happen when someone tries to enter a number with more than 10 digits, and for every other case except the ideal one.

3. Boundary Value Tests

These tests somehow have the specific objective of checking the system’s behavior when there are boundary values or data limits set for different components of the system. For example, if the minimum character limit is set as 8 for an input data type, the boundary value tests should check the response of the system when any data is entered in a format other than the set boundary values. If the entered inputs are less than the boundary values, the tests are considered negative testing.

4. Decision-based Tests

As the name suggests, these tests check for the accuracy of an outcome based on a decision taken. That means these tests will ensure that the expected results are being received when a particular condition is met. For example, if we consider the case of image uploading that we saw in the previous part, the decision-based tests that can be performed are -

  • If the user enters incorrect login details, the page will show warnings about incorrect details. Sometimes, the entire page should be reloaded.
  • If the user enters the correct login details, the system should let the user enter his/her profile and take the user to the home page.
  • If the user enters the correct login details but cancels the login, the system should not open his/her profile and instead should reload the login page.

So, similarly, numerous test cases can be created based on the huge number of decisions possible to be taken at any point of operation.

5. Ad-hoc Tests

The specialty of these tests is that these tests are expected to put light on the issues that were not identified earlier by any other test. These tests usually have the target of breaking the system and checking how it responds. For example, if a user instructs the system to delete or deactivate his/her account while being logged in and performing other tasks. So, the actions of the system in such a new situation are tested through ad-hoc tests.

Functional Testing Best Practices

The best practices that you can follow for functional testing are the following.

Pick The Right Test Cases

As the world is effectively adopting test automation for most tests, it is also highly important to know which test cases should not be automated in order to get the best results. For example, test cases that require some specific setup or configuration during or before execution should not be automated. Now, considering such different conditions you must pick the right test cases for automating. Some of the most suitable types of tests that should be automated are -

  • The same tests that need to be repeated with different data.
  • Test cases that are completely repeated.
  • P1, P2 test cases that consume much time and effort.
  • Same tests that are repeated in different platforms like different operating systems, browsers, devices, etc.
  • Tests that are prone to human error.

Have A Dedicated Automation Team

Automation is a blessing when it is properly done. That means if you are willing to get the benefits of test automation, you must ensure that the automation measures are completed by expert professionals who have the proper knowledge, skills, experience, and tools. Hence, make sure to have expert QA professionals in your team or if you want to save your time & resources, consider using advanced AI-based low-code test automation tools like Preflight that can enable anyone to create, run, and maintain automated tests without any coding knowledge.

Perform Data-Driven Tests

Automated tests that use multiple data sets should be written in such a way that they are reusable. For that, the test data can be written in XML files, text, or property files, or read from a database. You can create a structure for the automation data to make the framework easier to maintain and the test scripts more effective for reuse.

Always Be On The Lookout For Breaks In Tests

Your test cases and the test automation tool must be capable of adapting to potential UI changes. For example, an earlier version of Selenium used the location to identify UI elements. Now, if for any reason, the locations of those elements change, the tests will eventually fail. Hence, you must use AI-based automated testing tools like Preflight that use advanced context awareness to understand the objective behind a webpage and adapt to every change in the UI.

Test Frequently

Adapt the practice of preparing an automated test bucket and strategize frequent execution of that bucket. Such a practice can make you have a robust QA and leads to easier detection of more bugs.

Functional Testing vs Non-functional Testing

Functional Testing

Non-functional Testing

These tests are performed using the functional specification provided by the client and they ensure that the system fulfills the functional requirements.

These tests check the performance, reliability, scalability, and other non-functional aspects of the system.

Besides automation tools, manual testing can also be used.

Automation tools are the best choice for these tests.

Functional tests are executed first.

Non-functional tests are executed after the functional tests.

Functional tests describe what the product does.

Non-functional tests describe the performance of the product at whatever it does.

Business requirements are used as inputs for functional tests.

The inputs for non-functional tests are the performance parameters like speed, scalability, etc.

Manual functional tests are easier to perform.

Manual non-functional tests are difficult to perform.

Examples of functional tests are -

  • Unit testing

  • Integration testing

  • Smoke testing

  • Sanity testing

  • Black box testing

  • White box testing

  • Regression testing

  • User Acceptance Testing

Examples of non-functional tests are -

  • Performance testing

  • Load testing

  • Stress testing

  • Volume testing

  • Installation testing

  • Security testing

  • Compatibility testing

  • Penetration testing

  • Migration testing


Functional testing is one of the essential parts of the entire software testing process and you must follow efficient strategies for the best results from these tests. Make sure to use advanced low-code test automation tools like Preflight to have your entire product team working on the testing works collaboratively regardless of their coding knowledge.

For more information about this amazing tool and more awesome products from us, make sure to check out our website, and feel free to contact us for any queries. Also, if you like to read informative technical articles, do consider visiting our blog page.