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Visual Testing vs Functional Testing: Key Differences

Developing a software application is not an easy task. It goes through various testing processes. As a testing team, you must make the software application usable for various users and devices. There are hundreds of devices and web browsers available. And these are used by millions of users across the globe. So, the organization needs to prepare its software applications for use by all these users. You can not restrict users to a specific web browser or device. Because it will lead to user migration from similar companies, it will be a loss to the company. 

Two of the most important testing processes are visual testing and functional testing. These kinds of tests check assertions against desired outcomes. You build software to behave a specific way, and you write tests to ensure that it continues to do so, even as your application grows. Visual testing is a software testing process that ensures the visual components work properly in all web browsers and devices. 

Functional testing is a software testing process that checks whether the application is working as intended.

Each function is compared to the corresponding requirement to ascertain whether its output meets the end user’s expectations. Both these testing processes are essential parts of developing a fully functioning and compatible with various devices and web browsers. In this article, you will see what visual testing and functional testing are, and then you will see the key differences between visual testing and functional testing.

What is Visual Testing?

Visual testing is also known as visual UI testing. It is a type of software application testing in which the testing and QA team ensures that all the visual components of the software application are correctly working, as well as various types of devices’ operating systems and web browsers. As we know, different web browsers accept the visual and CSS components differently. All the elements of a software application or website appear as intended during the development. 

Visual testing helps ensure that each element on the page appears in the right shape, size, and position, helping developers create a unified user experience. Visual testing also helps identify visual dependencies or bugs. It uses various approaches, such as pixel-to-pixel comparison, DOM comparison, etc. You can just compare what it is intended to be and how it looks currently. Ultimately, this helps ensure their product meets usability standards and is fully optimized across platforms.

Using visual testing in the software application development phase, you can ensure that the end user gets the best possible user experience and that all the features and functionalities are working correctly. The field of AI and cloud computing is growing rapidly. You can implement cloud-based tools and frameworks to execute the visual testing. Cloud-based visual testing has several advantages, such as increasing testing scalability. With cloud-based testing, you can also manage the cost of resources, as you need to pay for only those you use. So, after using these resources, you can unsubscribe, and extra money will be used for that.

Advantages of Visual Testing 

  • The various advantages of implementing visual testing are as follows:
  • It increases the code quality and provides a better user interface for the software application.
  • It helps to detect any kind of rapid bugs and errors.
  • Using visual testing, you can reduce manual code testing.
  • It ensures fast and easy implementation.
  • It provides control of views on different devices and browsers.

Disadvantage of visual testing

Now, let us briefly examine the various disadvantages of visual testing.

  • One major drawback of visual testing is that it cannot detect smaller defects and errors. 
  • Implementing visual testing for your software application requires very few skills.
  • While performing visual testing, there are some situations in which the video recording is not clear, which creates issues in performing the visual testing, and hence the result may be improper.
  • There are possibilities of containing the detection even though testing has been implemented.

What is Functional Testing?

Functional testing is a type of software application in which the testing and QA team checks if the functionality of the software application is working correctly or not. The ultimate goal of functional testing is to make sure that the software application performs according to the development it was made for. Generally, it has nothing to do with the internal coding or something internally. For example, you can use the Black Box Testing technique to check whether a provided input returns the output as intended to be. Functional testing is a very important part of the software development cycle because you need to perform this testing to understand whether your application functions as intended accurately. 

There are various types of functional testing. Let us have a brief look at these functional testing types in the section below. 

Unit Testing: Unit testing is the testing in which you break the desired outcome into separate units. Doing so allows you to predict any minor issues as you check if the small number of inputs are working properly output or not. As the name suggests, unit testing is done to precisely perform smaller tests and then merge them to get a proper testing result.

Smoke Testing: Smoke testing is used to check the software application’s functionality at a basic level. When you perform smoke testing, it is first passed to the testing process and is not intended to be exhaustive. If the application is not operational at a basic level, you do not need to proceed with the detailed testing. The software application can be moved to the development team for review. 

Sanity Testing: Sanity testing is a cousin to smoke testing, as it is also intended to verify basic functionality and potentially avoid detailed testing of broken software. The difference is that sanity tests are done later to test whether a new code change has had the desired effect. It is a “sanity check” on a specific change to determine if the new code roughly performs as expected. 

Integration Testing: This testing process is defined as a combination of whether software modules are working properly or not. The individual modules have already passed the independent tests, but they are still dependent on other modules for successful operation. This kind of testing is termed integration testing. 

Regression Testing: Regression testing is a software testing technique that re-runs functional and non-functional tests to ensure that a software application works as intended after any code changes, updates, revisions, improvements, or optimization. Visual regression testing can be performed using cloud-based utilities like LambdaTest for more beneficial testing output.

LambdaTest is a comprehensive test orchestration and execution platform that leverages artificial intelligence to facilitate the seamless and efficient running of manual and automated tests on a large scale. Focusing on providing a versatile testing environment, LambdaTest empowers users to conduct both real-time and automated testing across an extensive array of environments, encompassing over 3000 configurations, including browsers and real mobile devices.

The platform supports automated testing, allowing users to script and execute test scenarios. This is instrumental in achieving faster and more reliable test execution, especially for repetitive and regression testing tasks.

LambdaTest supports cross-browser testing across many browsers, ensuring that web applications are compatible and function seamlessly on different browser versions. This is critical for delivering a consistent user experience to a diverse user base.

It extends its testing capabilities to real mobile devices, providing a realistic environment for testing mobile applications. This includes testing on various devices, operating systems, and screen sizes, addressing the complexities associated with mobile app development.

Advantages of Functional Testing

The various advantages of using functional testing are as follows:

  • Functional testing allows the testing and QA team to develop a defect-free product.
  • Functional testing ensures that the end user is getting the right software application and is user-friendly in terms of functionality.
  • Functional testing allows the delivery of software applications with security and safety.
  • It ensures the proper functioning of all the functionalities of an application/software/product.
  • Testing the features and functionality also improves the software quality.

Disadvantages of Functional Testing

  • The various disadvantages of functional testing are as follows:
  • When you perform the functional testing, some critical and logical errors may be missed in the system.
  • Functional testing does not guarantee that your software application will go live. Because there are other tests still required to develop the software application successfully. 
  • The possibility of conducting redundant testing is high in functional testing.

Key Differences Between Visual Testing and Functional Testing

Now, let us examine the various parameters that show how visual testing differs from functional testing.

1. Testing Objectives

The first point to be considered when defining visual and functional testing is the testing objective. Visual testing ensures the visual components and checks if the visual elements are correctly working across different types of web browsers, devices, and their versions. You can check any kind of visual defects and bugs by comparing the testing results with previous ones.

The goal of functional testing is to test the functionality of a software application or website. For example, if you add functionality to your website and need to check if this function is properly working with all web browsers and various devices, you will perform functional testing. Many types of functional testing help the QA team make their software application work fully. Some are Integration testing, regression testing, etc.

2. Test Cases

The next key difference is the test case that we use to perform visual testing and functional testing. Visual testing is done using screenshots of the software application as a test case. These test cases help the testing team find any differences in the software application before and after applying the code changes.

Functional testing does not use screenshots as a test case. Instead, you must create tests based on user features and functional requirements. Basically, you perform testing based on user feedback. The test cases of functional testing may be inputs, outputs, etc. 

3. Tools and Technologies

Tools and technology are another important aspect of any testing process. The tech and tools we use have a great impact on the testing results. For visual testing, you need specialized tools to help you compare screenshots and other visual aspects. Some concepts used in visual testing are pixel diffing algorithms, visual validation libraries, etc.

On the other hand, functional testing uses various testing tools that help to detect and rectify errors and bugs related to the features and functionality of the software application. The various test frameworks and tools used in functional testing are unit testing frameworks, API testing tools, and behavior-driven development (BDD) frameworks. Both manual and automated testing approaches are used in functional testing.


Visual testing and functional testing are both very important aspects of software testing. Visual testing helps to ensure the visual components appear as intended. In contrast, functional testing is used to check the features and functionality of the software application and ensure it is working correctly after bringing any updates. What are the differences between visual testing and functional testing?

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