Functional Testing Vs Integration Testing – Key Differences

When a software is in the testing phase, different types of testing techniques and methodologies are followed on different layers. Two such types of testing are functional testing and integration testing. Both play a significant role in ensuring the quality of the product and delivering a top-notch product. In this article, we will discuss functional and integration testing – when to perform them, the benefits of executing these tests, and then the key differences between them.

Difference Between Functional and Integration Testing

Functional testing helps verify that the software works as expected and meets user’s expectations. It is a type of black-box testing that involves testing various aspects of the application, such as user interfaces, APIs, databases, and other system components, to validate that they are working as expected. It doesn’t involve looking into the internal working of software functions – just observing output on the appropriate input.

Integration testing is when two or more components are integrated and tested as a whole. It ensures that smaller components are working correctly together after integration and provides an error-free user interface for the end users. It helps to improve the performance and scalability of the software and increase the overall software quality.

Read all about Integration Testing

Functional Testing vs Integration Testing: Purpose

Purpose of Functional Testing

Functional testing helps verify that the software meets the functional requirements. It ensures that the software behaves as expected and aligns with the business requirements. 

It checks everything like the end-to-end workflows, functionality of the application, APIs, database, client-server communication, security, etc. Every functionality is tested with different inputs, and the test result will be compared with the expected output.

Purpose of Integration Testing

Integration testing helps test the interactions between different software modules after they have been individually tested. 

The main aim of integration testing is to ensure that the integrated components work together as intended and to identify any issues that might arise due to their interactions. Typically, integration is done after unit testing. 

Functional Testing vs Integration Testing: Workflow Comparison

Let’s take a look at the workflow difference between the integration test vs functional test,

Functional Testing Workflow

• Understand the software requirements and functional specifications provided by the development team or stakeholders.
• Create test cases that cover different functional aspects of the application and test scenarios.
• Now, create a document for the traceability matrix after designing the test cases.
• Create test data and start executing test cases.
• Once the test is complete, compare the actual result with the expected result to validate if the product works as it is intended to be.

Integration Testing Workflow

• Understand the requirements and specifications provided by the developers.
• First, divide the application into smaller modules and understand each module’s functionality. 
• Next, find where you start and finish in each part and create a test plan. 
• Choose the best integration testing approach based on the app’s needs and identify test conditions.
• Then, start to design test cases to perform integration testing and analyze the results.

Functional Testing Vs Integration Testing: Use Case Comparison

Functional testing and integration testing are both critical aspects of the software testing process, but they serve different purposes and focus on different aspects of a software application. Let’s consider different use cases to understand this,

Functional Testing Use Case

Use Case: Consider you are testing an e-commerce application’s shopping cart functionality.

• User Scenario: Add to Cart Functionality
• Test Description: Test the cart’s functionality. That is, when a user adds a product to the cart, the cart should be updated with the correct name, price, and quantity of the product.
• Expected Result: The application should accurately update the cart and show the correct product details.

Integration Testing Use Case

Use Case: Consider an e-commerce website where users can browse products, add them to their cart, and proceed to checkout. The website is made up of several components: a product catalog, a shopping cart, a user authentication system, and a payment gateway.

• User Scenario: Test the interactions between these components to ensure they work as expected.
• Integration Test: Test the cart module, checkout module, etc. That is, adding multiple products to the cart and verifying the cart’s accuracy. Next, add a product to the cart, log out, and then log in again to ensure the cart items are retained. Then, add products to the cart, proceed to checkout, and verify that the payment gateway works correctly.
• Expected Outcome: The user should be able to browse products, add items to the cart, login, proceed to checkout, and complete the payment.

Challenges of Integration Testing vs Functional Testing

Let’s take a look at the challenges between integration testing vs functional testing,

Challenges of Functional Testing

• Designing comprehensive and effective test cases for all possible functional scenarios can be complex and time-consuming. 
• Functional testing can become complex when requirements change frequently, requiring constant updates to test cases and test data.
• Functional changes or bug fixes in one area of the software can unintentionally impact other areas. Ensuring that new functional additions don’t break existing functionality requires robust regression testing. Get here the Comparison between Regression Testing vs Integration Testing
• Defining clear test requirements for every change is difficult due to the detailed and measurable information they contain.
• Keeping a simple report to decide whether something works or not with functional tests might not work well. This is because reports are divided based on features and defects.
• It takes a long time to fix recurring issues and to set up the test environment.
• Creating test metrics to analyze and improve applications is challenging due to software complexities and varying test requirements.

Challenges of Integration Testing

• When you replace mock data with real modules, you might find new bugs.
• It is time-consuming and needs good coding skills to create integration tests because programs and data required for testing are mocked. 
• It is difficult to understand the logic because the software code is written by multiple teams separately.
• It is difficult to understand the code because it is written by different teams separately.
• Testing integrated parts of the software is complicated because various things like the database, platform, and software environment affect the tests.
• Choosing the right testing approach can become harder when you have multiple options to consider.
• Integration testing gets even more complex when external features, tools, and libraries from different companies with their own dependencies are involved.

Core Differences – Functional Testing Vs Integration Testing

The table below depicts the integration test vs functional test core differences,

Functional Testing	Integration Testing
Helps verify that the software is functioning as expected and meets the user’s requirements	Helps test how different software modules interact with each other
Executed by testers	Executed by testers and developers
Helps identify issues that might interrupt the application’s working	Helps identify issues that might occur while integrating different components
It is performed before integration testing	It is performed after unit testing and functional and before system testing
It is quite complex when compared to integration testing, as the entire application is tested.	It is less complex as we test the modules.
It uses the black-box technique.	It uses the gray box testing technique (both white box and black box testing)
Tools used – Testsigma, Selenium, Katalon, Tricentis, etc.	Tools used – Testsigma, Selenium, JUnit

When to Automate?

You should automate the functional and integration testing if you repeatedly execute the same functional and integration tests, and you see an ROI on automating them. Automated testing, when planned and executed well, reduces the total time and effort required to perform testing, thus accelerating the time to market, and also provides an ROI.

Testsigma is a powerful test automation tool that lets you automate web, mobile, and desktop applications in the same place. It is an AI-driven platform that lets you create test cases in plain English, which makes the testing 5x faster.

The following are some of the top benefits offered by Testsigma,

• It is a no-code test automation tool that lets you author simple and complex tests in simple English
• It is very simple and easy to use
• Also comes with a record and play feature to record user actions and later automate them as test cases on the cloud.
• Automate cross-browser testing across 3000+ real devices and 1000+ browser/OS combos.
• A no-code test automation tool that does not require coding to write test scripts
• Automate your web, mobile, desktop, and API tests in one place
• Easy test maintenance on the cloud
• No need to download any tools or frameworks
• Supports parallel test execution

Testsigma is also available as an open source and free version.Start automating your functional and integration tests with Testsigma Open Source

Wrapping Up

Functional testing and integration testing are closely related to each other, but they are not the same. We hope that this article helped you understand them and their differences better.

Frequently Asked Questions

Is functional testing manual or automation?

Functional testing can be both manual and automated. Manual functional testing involves human testers executing test cases manually to verify the software’s functionality. On the other hand, automated functional testing involves using automation testing tools to execute test cases and compare actual results with expected results. Automated functional testing is typically faster, more efficient, and repeatable than manual testing.

Is integration testing the same as UAT?

No, integration testing is not the same as user acceptance testing (UAT). They both serve different purposes in the SDLC. Integration testing is focused on verifying the interactions between different modules of the application, while UAT is focused on validating the software from the perspective of end-users.