Functional Testing VS Unit Testing – Comparison with Examples

October 17, 2024

Functional Testing VS Unit Testing – Comparison with Examples -Testing is a process or system for identifying characteristics and problems. It is considered the backbone of software development. Testing is crucial, as it helps identify issues and defects in a product so that they can be fixed before the product is delivered. 

This also ensures that code behaves as expected and meets the requirements, ultimately guaranteeing the quality of the software. However, with so many available options, it can be difficult to determine which tests to use, from unit test vs functional test. 

You need to read the entire blog to decide between functional testing vs unit testing. This will help you gain insight into the specific scenarios in which each type of testing is relevant and complements the other. 

In this blog, you will find a simple guide to help you understand the different aspects of unit testing vs. functional testing. So, have a glance at the following simple and quick guide.

What is Functional Testing?

Functional testing is a procedure of testing software systems to confirm whether the software matches its design. It focuses on the entire system and determines how effectively it executes its intended functions, confirming whether it meets user expectations

Functional testing services aims to validate the system’s features, capabilities, and interaction with different components. It allows you to accurately verify the input and output, data manipulation, and user interaction, allowing testing of all the functions.

By running a functional test, you can detect bugs or glitches that developers might miss while building the app. Thus, functional testing is crucial information for software quality checks and prevents potential faults in fulfilling your users’ and business requirements.

What is Unit Testing?

Unit testing checks small code to deliver information early and often and focuses on individual units and components. It aims to confirm that each software unit functions as intended and fulfills the requirements.

Developers usually perform unit testing early in the development process before the code is integrated and tested as a whole system. This practice is well-liked and adopted by many organizations, and it is beneficial for eliminating bugs in code. 

Unit testing aims to review all code units and ensure they are bug-free and functioning correctly. This enables the project’s sustainable growth and execution to ensure expected behaviour and results. 

Difference Between Functional Test vs Unit Test 

Functional vs unit testing aims to identify and prevent defects and deliver a quality product. However, some qualities distinguish them. Below is the table to identify the difference between unit testing vs functional testing.

Key Factors to Differentiate Unit Testing vs Functional Testing

Testing aims to ensure the delivery of high-quality, efficient, and reliable products. It is a systematic and disciplined approach that helps identify and troubleshoot defects, errors, and issues during the development cycle. Below are the purposes of functional vs unit testing. 

1. Purpose

✅ Unit Testing Purpose 

Unit testing is an important step in the development process because its main purpose is to isolate written code and test whether it works as planned. It is easy to create and run and requires little cost. 

Unit testing aims to isolate the smallest testable parts of an API (Application Programming Interface) and verify that they function properly. From the developer’s perspective, unit testing is to build a robust codebase with minimal cost. 

Another vital factor is to provide documentation for high-level testing. High-level testing can confirm different behavioral characteristics of the system under test. However, it mainly verifies that the SUT (System Under Test) produces correct results. 

✅ Functional Testing Purpose 

Functional testing helps test the functionality of the entire software. It is performed to identify whether each application feature works according to the software requirements. The objective of testing is to check the system’s functionalities. 

It checks the entire application, hardware, and networking infrastructure, from the front UI to the back-end database. Functional testing is from integration testing, confirming that different parts work together as predicted. 

Unlike unit testing, functional testing doesn’t tell what is broken and where to locate failure in the codebase. While functional texting just informs that something needs to be fixed. 

2. Improving software quality

✅ Unit Testing 

Developers thoroughly understand the work and then write a test to run the new code. Unit testing offers a security net of tests, giving developers the confidence to refactor code. 

This makes it easier and safer to refactor the code by placing tests that ensure refactoring occurs without problems or disruption. It removes the risks of changing older source code. 

Unit testing forces developers to write modular, maintainable, and easily manageable code. It also provides great benefits, such as improved code quality and better team collaboration and productivity. 

For example, if a developer breaks the code in 6 months, they then can run the test to secure the code. This is how unit testing aids in preventing regression. Thus, unit tests help identify possible defects in your system through a bug report, so developers don’t need to invest extra time and resources in the long run.

✅ Functional Testing

Functional testing ensures that the entire system works as predicted. Each function is compared to the correspondence requirements, ensuring the critical app capabilities behave as expected. 

This type of testing includes various subsets, each offering specific benefits. System testing validates that the entire app or software is in the context of a real user. However, end-to-end tests increase coverage and reduce the risk of integrating new codes into an application. 

For example, integration testing ensures the smooth operation of all integrations. Another type of function testing is smoke testing, which helps you check essential software features, minimise regression, and save time.

3. When to perform

✅ Unit Testing

Although unit testing is a replacement for functional testing, it is the basis of the testing process on which the rest of the testing process should be built. Developers generally execute unit testing during the development stage. 

Test Drive Development (TDD) is a prevalent software development method that supports tests before the code. Over time, the advantages of writing unit tests have become apparent. 

✅ Functional Testing

Functional testing is performed when two modules interact with each other. After this, testers test features. It is performed in the project’s early phase that user requirements are freshest. 

Functional testing is on another level. This type of testing comprises various subsets, each offering specific benefits. It ensures that all the crucial user functionalities, such as sign-ups, logins, and purchasing workflows, are working as desired.

4. Type of Testing Technique

✅ Unit Testing

According to the purpose and definition of unit testing, it is a white-box testing technique. The system’s internal perspective and programming skills are used to design test cases. The criteria for this is to execute path and data structure sensitisation. 

Unit testing is a quality assurance technique in which application codes are broken into component building blocks. It is designed to test single units of code in isolation. Unit tests are easy and quick to create and help find and fix bugs in the early development cycle. 

✅ Functional Testing

Functional testing is considered a black-box testing technique. This technique tests the software’s functionality without noticing any internal code structure. Functional testing is performed against users or business requirements, comparing results with the expected outcomes.  

5. Purpose of Test Coverage

✅ Unit Testing

Test coverage in unit testing aims to catch most bugs before they make it to production. It reflects all the necessary parts of the software development process. The test coverage tool keeps track of the code that gets executed and does not. 

High code coverage gives developers confidence that the entire project is well-developed and maintained. It ensures that the test suite is comprehensive and all the critical functions of an application have been covered.

✅ Functional Testing

Functional testing can establish traceability between the requirements and test cases. Test coverage is the key element in evaluating the effectiveness of functional testing. 

It ensures that all necessary functions are tested, using various input parameters to test logic. Functional testing gives an indication of what features are implemented and how they satisfy the acceptance criteria. 

6. Complexity in Writing Test Case

✅ Unit Testing

In TDD (Test Drive Development), the complexity of unit testing has been seen. In TDD, developers must plan the code design based on your software requirements. Hence, if your code design is initially unclear, it will evolve and ask you to repeat the same test. 

For example, if you work with frequently changing algorithms, it would be best to delay unit testing until you understand the code design better.

✅ Functional Testing

In functional testing, you can mock out all the dependencies in different stories. Generally, developers split their time into parts: developing new features and fixing defects. 

A sustainable portion of the release is spent on testing functionality already released and used. The development of every new feature needs a test plan and maintenance efforts on existing tests. 

For example, testing a screen that processes data from the cellular network will not function without an internet connection, making executing a functional test very challenging in such cases.

Conclusion

Hope this guide has helped you to understand functional testing vs unit testing. Developers and testers must distinguish between the intent and scope of functional vs unit testing. Both tests are used for different purposes and have their limitations. So, to familiarise yourself with functional testing vs unit testing, read the complete blog.