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What’s the Difference Between Functional and Non-functional Testing

Every software built in this world is first tested before its release. However, how these software are tested is one question that comes to everyone’s mind. Software Testing is broadly categorised into two types: Functional and Non-functional testing. Testing is essential to software development since it guarantees the functionality, dependability, and quality of software products. To produce reliable and effective software solutions, developers, testers, and other external members or stakeholders must comprehend the distinctions between these two forms of testing.

But why are they important so much? Functional testing compares the operations of the application to a list of standards or requirements. Non-functional testing evaluates an application’s characteristics, such as performance, security, reliability, and dependability under load, that aren’t essential to functionality but still improve the end-user experience.

In this article, we will understand the differences between functional and non-functional testing. We will see how they differ in their testing methodologies, what things are tested in each, what techniques & tools are used, as well as the importance and challenges of both.

What is Functional Testing?

Functional testing is a type of software testing in which the software is tested for its functionality against the requirements and specifications. It is done to ensure that the software application is working with all the features and functionality defined in the user requirements. In simple words, it is done to make sure that all features of the software operate as intended and that the program acts as expected. Its main goal is to confirm the system’s functionality.

For example, testing the login functionality of a website where the testing is done against various test cases. The test may include validating the user input credentials to see if the required errors are received or not, testing whether the forgot password functionality is working, whether the email verification is done, etc.

Another example can be testing a calculator. In a calculator, we test the functionality of all the arithmetic operations and see if they work properly and produce the desired result.

Features of Functional Testing

1. Functional testing is done based on the user requirements and specifications to ensure all requirements are fulfilled.
2. It simulates real-world test scenarios to make sure that all the functionalities laid out in the SRS are working correctly.
3. Functional testing is also referred to as “black box” testing since it doesn’t require the tester to understand the application’s core logic or code.
4. Functional testing is done based on the inputs and the expected results.
5. It helps in validating the functionality of software efficiently.
6. It can be performed manually or using automated testing tools.

Types of Functional Testing

The given below testings are the various types of functional testing:

1. Unit Testing- This type of testing tests the smallest unit of an application. The part of the application is done in isolation. The unit testing is done during the development phase and is usually done by developers only. There aren’t many unit tests, though. Application-wide functional tests frequently identify changes in functionality that unit tests miss when the application deviates or regresses.

2. Integration Testing- Once the units of an application are tested, they are combined and integrated to test all together. It makes the application’s various modules or components communicate with one another properly by testing their interactions.

3. System Testing- In this testing, the complete system is tested as a whole to verify that the software system is working as expected and as per the specified requirements.

4. Smoke Testing- Smoke testing is an initial test to see if a software’s fundamental features work or not. It is a broad but shallow testing technique for testing the main functionality of a software product.

5. Regression Testing– This testing is done to ensure that new code changes do not affect the existing functionalities of the software. This testing addresses the common problem that every developer faces in its life cycle. It is a type of testing in the SDLC that runs after every change or modification to ensure that the modification introduces no unintended breaks in the application.

6. User Acceptance Testing- In this, the end users test the program to make sure it meets specifications and can perform necessary activities in real-world circumstances. This is also known as alpha or beta-level testing. It is done before the software is released into production.

7. Sanity Testing- Sanity testing, a subset of regression testing, verifies that a specific feature or bug remedy functions as intended. It is done to validate whether the changes done in the fewer parts of the application do not affect the existing application, and software still functions as expected after the change.

Techniques in Functional Testing

1. Equivalence Partitioning: To cut down on test cases and split input data into valid and invalid segments. In equivalence partitioning, the testers divide the inputs into classes or groups of data that are expected to output similar results.
2. Boundary Value Analysis: In this technique, the boundary values between the equivalence classes are tested. Here, we test the boundary values to look for off-by-one mistakes.
3. Decision Table Testing: This method involves representing and testing various input combinations and their corresponding outputs using decision tables. Here, we try to create test cases to cover every user condition.
4. State Transition Testing: Testing the application’s many states and the transitions between them is known as state transition testing.
5. Use Case Testing: To make sure the application functions as intended, real-world scenarios are tested based on the use cases.

What is Non-Functional Testing?

Non-functional testing is a type of software testing in which the software is tested against all the non-function test requirements. Non-functional testing checks to see if the system is acting as per the requirements. It tests all other aspects of the software which were not tested in the functional testing. The purpose of non-functional testing is to examine the non-functional features of a software application.

Non-functional testing is concerned with evaluating the software’s readiness and its ability to deliver a satisfactory user experience. It ensures that the software is providing the best performance to the user, with no security issues.

For example, Making sure the website stays responsive and stable in the face of numerous concurrent users or transactions is the fundamental objective of assessing a website’s performance under load. Doing this type of testing is essential to comprehend the behaviour of the website during periods of high traffic, such as during a significant sale or a product launch in scenarios like Amazon Great Indian Sale or Flipkart’s Big Billion Day sale events. To see how a website responds to an increased load, performance testing usually entails simulating a sizable number of visitors accessing the site concurrently.

Another example is to check for scalability. Evaluating a website’s scalability is determining whether it can expand and handle rising demand by adding servers, databases, or network capacity. Finding out if the website can smoothly grow to handle additional visitors, data, and transactions without experiencing a decrease in performance is the goal.

Features of Non-Functional Testing

1. Non-functional testing is done to ensure the performance of the software is stable under different conditions like stress, load, etc.
2. It evaluates against the non-functional requirements.
3. It is not mandatory but is preferred.
4. It helps in assessing the overall quality attributes such as reliability, usability, and maintainability of a software product.
5. It guarantees that the program meets customers’ expectations for speed, reliability, and performance while offering a positive user experience.
6. Non-functional testing helps in finding security flaws, usability issues, performance bottlenecks, and other non-functional defects before they have an impact on end users.

Types of Non-Functional Testing

The given below testings are the various types of non-functional testing:

1. Performance Testing- This testing is done to test the application’s performance under various conditions in terms of responsiveness and stability. It evaluates the program’s responsiveness to user requests, its capacity to handle traffic, and its performance in different network conditions.
2. Load Testing- To test for high traffic under expected and peak load, load testing is performed. Through load testing, a system’s ability to resist peak loads and gracefully fail in the event that it is not equipped to handle spikes in workload is verified.
3. Stress Testing- In stress testing, the system is put through rigorous testing to see how well it manages stress and bounces back from errors.
4. Scalability Testing- It is done to check whether the application can easily be scaled up horizontally or scaled down as needed.
5. Usability Testing- This is done to test the entire user experience, user interface, and ease of use of the application. It is possible to test if users can find the application’s basic functionalities on a webpage with ease.
6. Compatibility Testing- This kind of testing verifies if a system or piece of software is compatible with other systems or pieces of software, browsers, operating systems, etc.
7. Reliability Testing- It guarantees that the software operates without error over an extended period of time and ensures consistency. It verifies that under the stated circumstances and for the designated amount of time, the application can work without any interruption.
8. Compliance Testing- It ensures that the program complies with all applicable laws, rules, and standards.

Techniques in Non-Functional Testing

1. Benchmarking: In this, we compare the performance of the system as per the benchmark set against industry standards among other things.
2. Profiling: Profiling is done to analyse the system’s performance to find out the software bottlenecks and identify the areas for improvement in the software application.
3. Simulation: To test the software in the real world, we try creating a controlled environment and simulate the functionalities of the software to evaluate the system’s performance.
4. Monitoring: Testing is done to continuously monitor the system’s performance and identify issues and bugs in a real-time environment.

Importance of Functional and Non-Functional Testing

It is important to perform both functional and non-functional testing when delivering software. A lack of attention to one or the other results in partial verification and validation; this leads to a product that could be technically sound but not compliant with performance, security, or usability requirements. Therefore, it is necessary to implement both these testing techniques effectively, keeping in mind the following aspects:

• Quality Assurance: Functional testing aims at verifying that the software meets all specified requirements as per the SRS (software requirement specification doc) while non-functional testing focuses on guaranteeing good performance in different conditions. Having the focus of testing on each of their tasks, they can provide you with the best quality software.
• User satisfaction: Functional testing guarantees that the software possesses the features and functionality it is supposed to deliver, whereas non-functional testing is a positive user experience. Both testing techniques satisfy the user only if the software possesses the required functionality of features and performs well with no security, performance, or any other non-functional issues.
• Mitigation of Risks: Through functional testing, we can spot defects or issues related to specific functionalities. However, risks related to performance, security, and reliability can be managed with non-functional testing.
• Costs Reduction: Both functional and non-functional testing ensures that the development costs of the organisation are reduced before putting into production. When the product is tested before the release, costs can be reduced, otherwise, after release the software development costs can be increased 3 to 4 times the earlier testing cost.
• Compliance: Both these tests play an important role in establishing whether a system meets industry standards, regulations, and laws.

While functional and non-functional testing offers various advantages and is important for an organisation building software products, it also comes with various challenges. Here are some of the challenges in functional and non-functional testing techniques:

Functional Testing

1. Whenever the functional testing is done, it is done by creating different test cases. So, when frequent changes are being made, it creates a challenge to keep the test cases updated.
2. Testing one functionality may create another issue or bug simultaneously.
3. Testing complex interactions between different modules can be difficult and time-consuming.
4. Small modules of testing make the development phase more time-consuming and increase costs.
5. If the test plans and required functionality don’t match, it becomes very difficult to execute the test cases. The entire amount of time needed to adjust the test environment and ensure that the right configurations are supported.
6. Inconsistent reports from different team members and reports with low priority or severity mismatch may be another challenge.
7. Ensuring thorough test coverage to include all possible scenarios and edge cases.

Non-Functional Testing

1. Significant resources, including hardware, software, and qualified staff, are needed for this type of testing, particularly for performance and load testing.
2. It can be difficult to accurately simulate real-world test cases, and the outcomes might not always accurately represent user behaviour.
3. It might be challenging to manage and analyse the large amounts of data produced by this type of testing and becomes time-consuming.
4. Automation testing solutions may be necessary because managing this type of testing manually can be challenging.
5. Software must work with widely used browsers, operating systems, and other settings. If not, then there will be a compatibility issue.

Key Differences Between Functional and Non-Functional Testing

The given below are some of the key differences between Functional and Non-Functional Testing:

Conclusion

Testing for software is both with regard to whether it functions or not and irrespective of function, which are two major areas where an equal balance must be maintained. Functional testing guarantees that the software correctly executes its intended functions. The non-functional evaluates the performance, usability, and quality attributes of the software regardless of its correct functioning.

Both types of testing play a critical role in producing high-quality software that satisfies the user’s expectations and can perform well under any circumstances. In this article, we have seen the types and techniques of both functional and non-functional testing. We also saw the importance and the challenges of both types of testing.

Distinguishing between functional and non-functional testing helps development teams implement appropriate best practices for each, ensuring they address the reliability, security, and user-friendliness of the software— which otherwise might slip through the cracks. To ensure the best and defect-free software product, both types of testing need to be done effectively with a proper plan and environment.