Functional vs Non-Functional Testing Methods


Many engineers gravitate toward it when writing functional tests to complement their non-functional tests. The code that interacts with the outermost layers is tested automatically and only the output is evaluated. This process is simple for applications requiring only API testing, as the code simply makes API calls and evaluates the result.

In contrast, non-function testing verifies that the software conducts the processes correctly. However, you should always keep in mind that non-functional testing should not be viewed as secondary to functional testing. In most cases, the graphical user interface is the only way for the audience of your product to interact with it.

definition of non-functional test design techniques

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Functional testing helps assess business requirements.Non-functional testing helps assess the performance requirement. Functional testing is performed before your application goes live.Non-functional testing includes tests such as maintainability and documentation, which happen after testing. An integrated software testing process involves functional and non-functional testing, building extra confidence at each application layer. The thoroughness of non-functional testing can be measured through non-functional coverage. Non-functional coverage is the extent to which some type of non-functional element has been exercised by tests and is expressed as a percentage of the type of the element being covered.

When you’re designing a new user interface, consider using focus groups to evaluate different interfaces. You can start with mock-ups and flows drawn on paper, get opinions, and try HTML mock-ups next, to get early feedback. Non-functional testing is just as necessary as tests that validate functionality. definition of non-functional test design techniques Many teams consider non-functional testing a lower priority because the improvements it provides are less dramatic. A user may be annoyed if performance degrades, but they may still be able to use the software application. For the most part, usability testing is a manual process that does not scale well.


White box testing involves testing an application with detailed inside information of its source code, architecture and configuration. It can expose issues like security vulnerabilities, broken paths or data flow issues, which black box testing cannot test comprehensively or at all. At first, the simple cause/effect nature of functional testing seems almost too easy. Techniques such as equivalence partitioning and decision tables can help reduce the number of tests in a logical way without losing test coverage. For example, Enterprise Resource Planning applications are often large and complex with massive functionality.

However, under non functional testing, you check if the user can log in to the application within 3 seconds of providing a username and password. Both functional and non functional testing aim to deliver an application that is in line with your business requirements. These tests find issues in software design and architecture performance. But non functional testing checks things that aren’t covered in functional tests. A type of software testing called volume testing involves exposing the software to a significant amount of data. By increasing the amount of data in the database, volume testing is done to evaluate the system’s performance.

definition of non-functional test design techniques

Drivers, unit testing frameworks, mock objects, and stubs are used to perform unit testing. Functional testing is done to make sure that the functions of an app are working in conformance with the required specification. It is black box testing and does not go into the details of the source code of the app. In functional testing the focus should be on the user-friendliness of the main functions of the app. ” This method of software testing tests the functional requirements of an app, verifying whether the software works as per customer needs.

Step 3 – Design Tests

Still, some user acceptance testing is a vital part of testing procedures for most applications. It is typically viewed as a standalone testing technique and is not included in the functional or non-functional testing categories. It helps the engineer map out the testing process and decide on both functional and non-functional requirements of the product that need to be tested. Alternatively, we can perform checklist-based testing when the software product has relatively standard specifications and architecture.

The landing page supporting 5,000 users per hour must provide 6 second or less response time in a Chrome desktop browser, including the rendering of text and images and over an LTE connection. Performance and scalability are the two core non-functional requirements no system can do without. We provide a number of resources to help customers learn how to get the most out of our products, with free online resources, virtual classrooms, and face to face. From financial services to healthcare and biotech to government and defense and more, we work with our customers to address their specific needs. Repeat the steps involved in the dataset, configuration, request load, and scenario. The tester would choose all the needed valid inputs in a positive testing scenario.

Usability testing looks at five aspects of testing — learnability, efficiency, satisfaction, memorability, and errors. We can use non-functional requirements such as the expected performance output from the software or the application under test. This can include the time the software takes to operate a unique system. When you perform testing, you focus more on functional testing to test the product functionality.

Closed-box testing

Load testing focuses on the ability of a system to handle increasing levels of anticipated realistic loads resulting from the transaction requests generated by several concurrent users or processes. User acceptance tests, where end users execute a final check on the software. Ensure that your application or website is provided the required server resources to guarantee a high-quality user experience. JMeter not only supports testing web applications but also evaluates database server performance.

The vendor can perform their testing, but it is up to the customer to perform acceptance testing, which can be both functional and non-functional. It is common to use techniques such as risk-based testing, along with robust test tools to plan, perform and evaluate the testing of large and complex systems. CompatibilityThe type of project you’re working on dictates how much compatibility testing is required. If you have a web application and your customers are worldwide, you will need to think about all types of browsers and operating systems. If you are delivering a custom enterprise application, you can probably reduce the amount of compatibility testing, because you might be able to dictate which versions are supported.

Smoke testing is done end to end and not for a particular component as we do in insanity testing. When autocomplete results are available use up and down arrows to review and enter to select. With this attribute, the users who are coming back to your digital platform after an extended duration don’t need to find the information or details they’re looking for. Determines whether a product or system meets a defined set of standards.

Reliability Testing

In this context, having thousands of test cases could actually be a liability if they are simply single-condition cases, or if they have a level of redundancy to them. You will likely need to repeat your tests in the event you need to retest a bug fix, or for the purpose of regression testing. Another benefit of designed and documented tests is repeatability and consistency. The “be” side of the picture is the attribute or behavior perspective, which can be tested by “non-functional” or attribute/characteristic tests.

We’ve already covered different types of software requirements as well as written a detailed post on the differences between functional and non-functional requirements. This time we’ll focus on non-functional ones, provide examples, and explain how to approach and document them. If you need a general recap on software documentation and planning, check out our video. There is no one-size-fits-all solution to testing software applications. It is too rigid to say that the functional method is better than non-functional or the other way around. The most neutral approach to testing choices includes a comprehensive mix of functional and non-functional testing.

  • Although this is not an overly complex requirement, there are three conditions involved which can make the requirement a bit difficult to parse and understand.
  • This can be avoided with a good strategy and tools to perform functional testing and non-functional testing on the apps.
  • When developers write code as loosely-coupled modules — as it usually should be — the components rely on explicit contracts for how they interact.
  • The parameters of non-functional testing are never tested before the functional testing.
  • Typically, we will test the functionality of the product first and then move on to its non-functional aspects.

It takes special skills and experience to actually find the right automation approach and tools, then to effectively implement them. InteroperabilityInteroperability refers to the capability of diverse systems and organizations to work together and share information. Interoperability testing looks at end-to-end functionality between two or more communicating systems. These tests are done in the context of the user—human or a software application — and look at functional behavior.


Exploratory testing is a sophisticated, thoughtful approach to testing without a script, and it enables to go beyond the obvious variations that have already been tested. Exploratory testing combines learning, test design, and test execution into one test approach. We apply heuristics and techniques in a disciplined way so that the “doing” reveals more implications that just thinking about a problem. As we test, we learn more about the system under test and can use that information to help us design new tests. Portability determines how a system or its element can be launched within one environment or another.

Game Development Report

By testing functionality early, you can save your company money by identifying design issues with specific functions before they become too costly. You can perform grey box testing using Interactive Security Testing tools. IAST tools combine DAST and Static Application Security Testing , which is used in white box testing to evaluate static code.

These tests can reveal defects where the logic has been incorrectly coded, or a business rule perhaps is not correctly understood. As in the previous example, where you may be testing values for a field where 1 through 10, you would want to test 0,1,10 and 11 if applying the “2-value” method . Performing end to end system tests in which you test a series of functions that are performed to complete a major functional task, such as ordering a product on a website as a new customer. Functional testers must have a deep appreciation of the end user’s thought process.

Keeping in mind there are no completely failure-proof applications, define the threshold that you can’t cross. Availability describes how likely the system is accessible to a user at a given point in time. While it can be expressed as an expected percentage of successful requests, you may also define it as a percentage of time the system is accessible for operation during some time period. For instance, the system may be available 98 percent of the time during a month. Availability is perhaps the most business-critical requirement, but to define it, you also must have estimations for reliability and maintainability.

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These non-functional tests ensure stable performance under any circumstances. Jmeter is one of the most used performance testing tools for developers. Available in an open-source format, it is easily accessible to software companies of all sizes.

Hence you need to document the non-functional requirement properly. When you perform the test properly, you can also get high-end satisfaction in terms of potential customer usability. Endurance testing, which measures system performance when subjected to maximum loads over time. Ultimately, functional testing and non-functional testing coexist, but the depth of coverage varies. This is where automated visual regression tools like Diffy come into play.