Non Functional Testing – A Detailed Overview

May 10, 2024Yamini Priya
Non Functional Testing - A Detailed Overview

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Imagine you’re driving a car with the engine roaring, the wheels spinning, and the wind blowing through your hair. Everything might seem perfect until you step on the brakes, and it takes 10 full seconds to bring the car to a stop. Conducting thorough testing can help detect such flaws. Non functional testing, here, will help test the braking system’s response time, how well it works, how effective it is, its performance, and so on.

Similarly, non functional testing in software testing helps understand how well the product works. It is the process of testing a product to evaluate its performance, reliability, usability, and other aspects that are not directly related to its functionality. It is like putting your car through a rigorous set of tests to ensure that it handles all expected and unexpected situations well.In this blog, we will explore various aspects of non-functional testing, its pros and cons, its different techniques along with non functional test cases example, and more.

What is Non Functional Testing?

Non-functional testing is a software testing type that tests the non-functional aspects of an application, such as usability, performance, scalability, reliability, security, compatibility, and more. In contrast, functional testing focuses on testing its functional behavior.

Simply put, non-functional testing checks the product’s quality rather than its features. You need to understand the impact that non-functional testing has on a product. In the world of software development, non-functional testing is as necessary as functional testing. Without it, a system may work perfectly fine in a controlled environment but may fail spectacularly in the real world.

Why Non Functional Testing?

Both functional and non-functional testing are important for every newly developed software. Functional testing ensures that the internal functions work correctly, while non-functional testing checks how well the software functions in the external environment.

It helps check non-functional aspects like performance, stability, responsiveness, portability, and more.

Non-functional testing assesses software installation, setup, and execution. It gathers measurements and metrics for internal research and development. This testing provides in-depth insights into product behavior and technologies used. It helps reduce production risks and associated software costs.

To understand this better, let’s consider situations that focus on testing the non functional aspects of the application,

  • How does the application work under normal load?
  • What happens when many users log in at once?
  • Can the application handle high stress?
  • Is the application secure from potential threats?
  • Can the application recover from disasters?
  • Will the application work the same way in different environments or operating systems?
  • Is it easy to port the application to another system?
  • Are the user manuals/documents easy to understand?

Importance of Non Functional Testing

Non functional testing is of crucial importance in the software development and testing process. While functional testing ensures that the software meets its intended functionality, non-functional testing validates other critical aspects of the system. 

Non functional requirements were not given proper importance in the initial test cycles, but now it has changed for good. 

Non functional testing is crucial to identify all the performance and security-related issues. It focuses on the non-functional aspects of the application. For example, using performance testing is a type of non-functional testing that lets you check the performance of an application under heavy traffic or user load. Also, it helps ensure that your application is stable and can handle heavy loads.

Non Functional Testing Example

Let’s take an e-commerce website as an example to understand how non-functional testing plays a vital role in product quality.

The website works well on normal days. But how should the website prepare for a sale day? To ensure this, the QA team will have to estimate the maximum number of people expected to visit the website in one day.

Also, they would have to estimate the average visits expected in a day. Then the website will be tested for a maximum and average load. The website should have to work well at the highest expected load, and the website should continue functioning if it is subjected to an average load over the period of the sale.

Characteristics of Non Functional Testing

The key characteristics of non functional testing are as follows,

  • Non functional testing has to be quantifiable. Hence using subjective terms like “good,” “better,” “best,” etc., will not be suitable for this type of testing.
  • It may not be possible to determine the precise figures at the beginning of the requirement process.
  • Prioritizing the requirements is highly important.

Objectives of Non Functional Testing

Some of the objectives of non functional testing are,

  • To improve the performance, usability, portability, efficiency, and/or security of the product.
  • To help minimize the cost related to the non-functional aspects of the application.
  • To reduce the production risk associated with the non-functional aspects.
  • To improve the understanding of the product’s behavior and technologies used.

Non Functional Testing Parameters

Non functional testing parameters typically include the following parameters, as shown in the image below,

Non Functional Testing Parameters

Let’s discuss some of these parameters in detail below.

1. Security

This parameter defines how a system is protected against planned and unplanned attacks from internal and external sources. This can be tested via Security Testing.

2. Reliability

This parameter tests the ability of a system to consistently perform its intended functions without failure for a specific period of time. This can be tested via Reliability Testing

3. Survivability

This parameter defines the ability of a product to continue functioning and recover itself in the event of any failure or disruption. This can be tested by Recovery Testing

4. Availability

It determines the extent to which a user can rely on the availability of the system and its functionalities during its operation. Stability Testing measures this parameter.

5. Usability

It refers to the level of ease with which a user can interact with a product in terms of learning, operating, and preparing inputs and outputs. This aspect is evaluated via Usability Testing.

6. Scalability

It determines the ability of a system to scale up or down based on the workload without affecting performance. This can be tested via Scalability Testing.

7. Interoperability

This parameter defines the ability of a system to interface with other software systems. This can be checked by Interoperability Testing.

8. Efficiency

It identifies the degree to which a software system can handle quantity, capacity, and response time.

9. Flexibility

Flexibility determines the application’s ability to work seamlessly across various hardware and software configurations. For example, most applications would require minimum RAM and CPU requirements to work.

10. Portability

It defines how easily an application can migrate from one hardware or software environment to another.

11. Reusability

It refers to a part of the software system that can be reused in another application.

Non-Functional Testing Techniques

Non-functional testing focuses on aspects of an application that do not involve specific behaviors or functions but instead evaluate attributes like performance, reliability, scalability, and usability. Here are some common non-functional testing techniques:

Compatibility Testing 

This testing ensures that an application works well with other software, operating systems, and related components. For example, QAs will check if the application is compatible with Windows, Mac, Linux, etc.

Portability Testing

Portability testing evaluates how easily an application can be moved from one environment to another.

Compliance Testing

This testing aims to verify that the software application complies with specific standards, such as Sarbanes-Oxley or HIPAA. 

Endurance Testing or Load Testing

This testing ensures that the application can handle a continuous load over a long period of time. For example, consider testing a banking application to ensure it remains stable under continuous expected load.

Performance Testing

This type of testing helps validate that the application meets specific performance goals, like response time, average load time, or throughput. It helps identify and fix any performance-related bottlenecks.

Security Testing

This testing ensures that the application is secure from unauthorized access, attacks, or other potential risks. Testers usually perform security testing to identify vulnerabilities in the application’s security system.

Stress Testing

This testing evaluates whether the application can handle unexpected or unusually heavy user load, such as an extremely large number of concurrent users trying to log in.

Scalability Testing

This testing ensures that the application can scale up or down to meet changing business requirements. An example is measuring the application’s capability to scale up or out in terms of non-functional capacity.

Penetration Testing

This testing helps simulate real-world attacks to discover vulnerabilities that might be exploited by malicious actors. Check out the top penetration testing tools available in the market.

Usability Testing

This testing ensures that the application is user-friendly and delivers the expected results. For example, checking whether the users can easily navigate to the “Buy Now” button on an e-commerce website. Usability testing can also be done remotely, which is known as remote usability testing, so different users from different geographical locations can participate in testing.

Volume Testing

This testing ensures that the application can handle a large volume of data. 

Recovery Testing

This testing verifies that the application can recover from failures or data loss.

Reliability Testing

This testing checks that the application can work without failures for a specified period in given environmental conditions.

Baseline Testing 

This testing ensures that the application’s performance does not degrade over time with new changes.

Documentation Testing

This testing involves evaluating the documented artifacts developed before or during the software testing process.

Localization Testing

This testing evaluates the application’s performance and quality for a specific culture, making the product appear natural for the foreign target audience.

Internationalization Testing

This testing ensures that the application can adapt to different cultures and languages worldwide without requiring modifications in the source code.

Example Test Cases: Non Functional Testing

Let’s understand this concept better with some non functional testing examples for different non functional testing types. The below table will demonstrate the various non functional test cases for web applications.

Test Case #Test CaseDomain
1Check if the application’s response time is not more than 5 seconds for up to 500 users using the application simultaneously.Performance Testing
3Check if all the web images have alt tagsAccessibility testing
2Check if the application is installable on Mac, Windows, and LinuxCompatibility Testing
4Check if user authentication and authorization mechanisms are robustSecurity testing

Checklist of Non Functional Test Cases

A checklist helps ensure that every aspect of the application is tested. It is mostly used when there is no proper documentation for testing or time constraints.

Checklist for Performance Testing

A performance testing checklist helps ensure that all essential aspects of performance testing are covered during the testing process. Here’s a comprehensive checklist for performance testing,

Response Time: How fast the application loads and processes inputs.

Throughput: The number of transactions completed during a load test.

Environment Setup: The testing environment should match the live environment for accurate results.

Process Time: Examining the time taken for activities like importing/exporting data or performing calculations in the application.

Interoperability: Verifying compatibility with other software or systems.

ETL Time: Time taken for data extraction, transformation, and loading from one database to another.

Load Handling: Checking the application’s performance under increasing load.

Checklist for Security Testing

A checklist for security testing typically includes the following,

Authentication: Ensure only authentic users can log in.

Authorized: Verify users can access only authorized modules.

Password: Validate password criteria, such as length and special characters.

Timeout: Test if the application times out after a specific period of inactivity.

Data Backup: Ensure data backup is scheduled and stored securely.

Internal links: Ensure internal links to the web application are not directly accessible from the browser.

Encrypted Communication: Verify all communication is encrypted for added security.

Checklist for Documentation Testing

Documentation testing is an important aspect of software testing, where the focus is on verifying the accuracy, completeness, and usability of the software documentation. Here’s a checklist for documentation testing,

User Documentation: Check and validate user manuals, guides, and instructions to ensure they are accurate, complete, and user-friendly.

Training Documents: Ensure they effectively cover the software’s functionalities and are easy for users to understand.

Advantages of Non Functional Testing

  1. Non-functional testing ensures better system security, protecting it from online threats.
  2. It guarantees the system’s ability to handle concurrent user loads, ensuring a smooth user experience.
  3. It enhances the system’s performance and efficiency.
  4. Test cases need not be rewritten since they remain unchanged, saving time and effort.
  5. Non-functional testing requires less overall time compared to other testing procedures.

Disadvantages of Non Functional Testing

  • Non-functional tests need to be repeated every time the software is updated.
  • Frequent software updates can lead to additional testing costs, making the software expensive.
  • Non-functional tests can be complex and challenging to execute, as it involves testing various aspects of the software beyond its core functionalities.
  • Unlike functional testing, non-functional tests may lack clearly defined pass/fail criteria, making it subjective and challenging to interpret results.

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Non-functional testing is a comprehensive approach that helps ensure that the application is optimized for user experience and meets the necessary quality standards. It helps developers to identify and address potential issues before the application is released to the public. That way, it reduces the risk of failure and ensures that the application meets the user’s expectations.

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Frequently Asked Questions

What is functional vs non-functional testing?

Functional testing verifies that the application is working as intended. On the other hand, non-functional testing checks how well the application works in terms of efficiency, performance, security, scalability, reliability, and portability.

What are non-functional testing examples?

Non-functional testing aims at testing the non-functional aspects of the product. To understand it in a better way, take a look at these examples,

  • Verify that the dashboard of the application loads within 5 seconds after login.
  • Check that the email notifications are sent within 3 minutes.
  • Verify that the 500 users can log in to the application simultaneously.

Is non-functional testing always carried out without documentation and test cases?

No, non-functional testing is not always carried out without documentation and test cases. Documentation and test cases are essential for effective non-functional testing to ensure proper planning, execution, and reporting of test results, like in the case of functional testing.

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