Detecting Functional Bugs: A Guide, Tools, and Implementation

In short: A functional bug is a discrepancy between what a feature is supposed to do and what it actually does. Detecting it early prevents it from affecting users and revenue. This guide explains what functional bugs are, how to detect them through functional testing, how they differ from non-functional testing, and a step-by-step process—from creating a test plan to choosing an automation tool.

Detecting functional bugs plays a crucial role in the software development process.

In this article, we’ll take an in-depth look at the detection of functional bugs, provide a step-by-step guide, and introduce some tools and best practices to ensure the highest quality for your websites and applications.

What are functional bugs?

Simply put, any component of an application or website that does not work as expected is a functional bug.

This refers to a discrepancy between an application's expected behavior and its actual behavior.

This can result in display errors or even crashes.

Some examples of functional bugs:

• A “Login” button that does not allow users to log in
• An e-commerce shopping cart that doesn't update properly
• A search field that does not return results
  

Functional bugs must be identified and resolved as early as possible in the development process to prevent faulty user flows in the production environment, where the damage caused by these bugs is more significant.

How can you detect functional bugs?

Of course, to identify functional bugs, you have to run functional tests! 🤓

There is a wide range of functional tests available to identify each type of functional bug.

Types of Functional Tests

Unit Tests

Unit tests are run by developers as they write code and build the application.

The goal is to validate the functionality of a unit or component by ensuring that the desired outputs are generated given a set of inputs. As the most granular type of test, it establishes a solid foundation for more complex functionalities.

Smoke Test

When a new build is complete, it is handed over to QA for smoke testing, during which only the most critical and essential features are tested to ensure they produce the expected results.

The smoke test adds an extra layer of verification to determine whether the new construction can move on to the next stage or needs to be reworked.

Integration Tests

Although modules and components may function properly on their own, QA teams must always ensure that they work together as a whole.

Since the components of a system are typically built separately by different developers, integration testing is essential to verify that they work together properly.

Regression Testing

Regression testing is designed to verify that new changes made to a software system have not introduced regressions—that is, errors or problems in features that previously worked correctly.

User Acceptance Testing (UAT)

User acceptance testing involves having end users or customers participate in validating the application or system to ensure that it meets their needs, functions properly, and is ready for use in a real-world environment.

UI/UX Testing

These tests are designed to verify that all user interface features work as intended. The goal is to ensure that buttons, links, forms, and all intended interactions respond correctly to user actions.

 

What is the difference between functional and non-functional testing?

Functional tests verify whether the specified functional requirements are met, while non-functional tests are used to test non-functional aspects such as performance, security, scalability, or application quality.

In other words, functional tests allow us to verify whether key features are working, while non-functional tests focus more on how operations are carried out.

How to Identify Functional Bugs Step by Step

Now that we've established what a functional bug is and the types of functional tests used, we'll outline the steps you need to follow to orchestrate your functional tests with confidence:

1. Planning and Design of the Testing Process

The first step is to define the parameters of your functional testing process.

What is the scope? Which steps in the process will you automate?

It is also at this stage that the budget and staff expertise are taken into account to develop a plan that aligns with your company's capabilities.

2. Choose an automated testing tool

Once you have defined your testing requirements, the next step is to research the various automated functional testing tools available on the market.

Among the best known are:

• Selenium
• Playwright
• Cypress
• Appium
• TestComplete
• Katalon
• Mr Suricate
• Ranorex
• Leapwork
• Tricentis
• LambdaTest

Although manual testing has its place in the development cycle, an automated testing tool allows you to speed up your deliveries while eliminating the risk of human error in your processes.

Key Features to Consider When Choosing an Automated Functional Testing Tool

Reporting Capabilities: Review all the reporting features supported by a tool.

Ease of Use: The importance of ease of use depends on your team’s skill level. A “no-code” automated testing tool is a solution for all types of users, even those considered “non-technical.”

Flexibility: To accommodate different types of tests, the tool must be flexible enough to support multiple testing frameworks, operating systems, and devices.

Technical Support: The supplier must provide adequate support and maintenance services, including updates.

Price: The price will depend on the type of tool—commercial or open source.

Open-source tools are distributed free of charge, but require technical skills to be used to their full potential.

Commercial solutions are generally easier to use and have teams to help you with test automation.

3. Create your test framework and customize the environment to suit your needs

The next step is to set up the framework and environment in which all your tests will take place.

This includes:

• Description of Testing Standards
• Defining the practices you will use
• Choosing Between Data-Driven, Keyword-Based, and Frequent Testing Methodologies

Setting up a test environment involves installing and configuring your testing tool.

It's also important to plan the schedule for the tests to make things easier for your teams.

4. Creating and Running Your Test Scenarios

Create test scenarios that cover all of the application's features, and run them.

The more comprehensive your tests are, the more likely you are to uncover potential functional bugs.

5. Bug Analysis and Reporting

Once the tests have been completed, analyze the results and prioritize the functional bugs based on their severity and their impact on the user experience.

Create detailed reports for each bug, including information on how to reproduce it, screenshots, and the steps to reproduce it.

6. Correction and Verification

The next step is to fix the identified bugs. Once the fixes have been made, run the tests again to ensure that the issues have been resolved and that no new bugs have been introduced in the process.

Detecting Functional Bugs – Best Practices

Select the right test cases

It is important to strategically choose which test cases you will automate.

For tests that require configuration before or during execution, it is best not to automate them.

As a general rule, automate the following types of tests:

• Tests that must be performed repeatedly
• The same tests with different data
• Tests Prone to Human Error
• The same tests on different operating systems, browsers, devices, etc.

Data-Driven Testing

Automated test cases that require multiple datasets must be written in a way that allows for reuse.

To do this, data can be written to sources such as XML files, text files, or property files, or read from a database.

Creating a structure for automation data makes it easier to maintain the framework. It also allows for more efficient use of existing test scripts.

Test frequently

Prepare a set of basic automation tests and schedule them to run frequently.

This allows QA team members to improve the automation framework and make it more robust.

Find Your Functional Bugs with Mr Suricate

By following a methodical approach, using automated testing tools, and carefully documenting issues, your teams can significantly improve your customers’ experience while protecting your brand image.

The no-code SaaS solution Mr Suricate a wide range of automated tests to help you manage your acceptance testing and provide your users with the best possible experience.

Take control of your applications and detect bugs in real-time across your websites, applications, and APIs by regularly reproducing your user journeys.

FAQ

What is a functional bug?

It is a discrepancy between a feature’s expected behavior and its actual behavior: a button that doesn’t respond, an incorrect calculation, or a form that doesn’t validate. Unlike a performance or security issue, it directly affects usability.

How can you detect functional bugs?

Through functional tests that simulate user flows and verify that each feature meets the requirement. By automating these tests, we run them with every update and detect regressions before they reach production.

What is the difference between functional and non-functional testing?

Functional tests verify what the software does (its features); non-functional tests verify how it does it (performance, security, accessibility, load). Both are necessary.

To see the solution in action, check out our functional tests.

See also: Why Can Functional Test Automation Fail?