Fundamentals of functional and non-functional testing

Functional and non-functional testing are at the core of the software testing lifecycle of any project. Functional testing focuses on testing all the functionalities and features of the application, while non-functional testing is responsible for testing its performance, stability, and usability, amongst others. These two testing types, though different, contribute towards making the application better and provide value to the end user.

Detailed analysis of functional and non-functional testing

Functional testing and its types 

Functional testing of an application deals with testing all its functionalities and integrations with other applications. Different modules of the application with various functionalities have to be tested individually. The different functional testing types are:

• Unit testing - Unit tests are the preliminary tests carried out during the initial stages of application testing. Individual modules are tested as a standalone basis without taking into account any other module of the application. Unit testing is carried out for every new functionality added to the application.

• Smoke testing - Once a new application build is ready, a basic set of tests are performed to check if it is devoid of any major errors. These tests, as part of smoke testing, are carried out to identify if the QA team can proceed with further testing.

• Sanity testing - Sanity testing is a precursor to regression testing. It focuses on checking if the recent code change works properly by performing basic tests relevant to the changes. Sanity tests make it easier for the QA team to decide whether to proceed with regression testing.

• Regression testing - Every time there is a major change to the codebase, either by addition of new functionality or bug fixes, there is a possibility that these changes might affect other functionalities or overall stability of the application. Regression testing is necessary to identify errors that arise.

• Integration testing - Each functionality or feature of the application has dependencies on other functionalities or third-party applications. Integration testing handles the testing of the integrations between the various functionalities and modules.

• System testing - For the application to function smoothly, all functionalities have to work cohesively as one entity. System testing is carried out after integration testing by checking the integrations between different modules of the application, and their integrations with third-party services. The entire application is tested thoroughly as one whole system to check if it meets the specified requirements.

• Acceptance testing - Acceptance testing is done towards the end of the testing phase before deployment. These tests are performed from the user's perspective by emulating the real-world scenarios to check if all the functionalities perform as intended before the application is made accessible to the end user.

Non-functional testing and its types 

Non-functional testing is responsible for checking every other aspect of the application beyond the functionalities and features. It deals with the performance of the application. The different non-functional testing types are:

• Performance testing - Performance testing is carried out after the functionalities are found to be working as per the product requirements. The focus is on evaluating the speed, performance, scalability, and responsiveness of the application.

• Load testing - In the real world, when a large number of concurrent users access the application, performance and stability might take a hit. Load testing artificially simulates the expected load or traffic on the application in a controlled environment to analyze the stats, which could help in making necessary changes.

• Stress testing - Stress testing is the process of pushing the application to its breaking point by steadily increasing the traffic or load until it stops performing efficiently or becomes unstable. This testing can help the team understand if better hardware is needed and even contribute towards improving the codebase that might make it resource-efficient.

• Security testing - Targeted hacking has become a major concern for businesses and individuals alike in this era. Therefore, focus is on building a robust system that can withstand a battery of sophisticated hacking attempts. Penetration tests and SQL injections are some of the important types of security testing.

• Volume testing - Volume testing, or flood testing, is accessing a huge amount of data on the application and accurately checking all the parameters that quantify its performance. This is similar to performance testing, but with greater load and advanced analysis of the metrics that evaluate the performance.

• Usability testing - Once the functionalities and their respective integrations are tested, the entire application needs to be tested in terms of how a user handles it. The application is tested by letting a group of users perform certain tasks on the application while they are monitored for gathering insights that are shared with the development team.

Advantages of functional and non-functional testing

Together, functional and non-functional testing can equate to saved time and resources, as they ensure errors are addressed during the testing phase itself before they become bigger issues that greatly affect the production phase.

Advantages of functional testing are:

• Early error detection - Functional tests are the initial set of tests performed in the STLC. Any changes to the codebase in the form of feature additions or bug fixes can lead to new errors, which can be easily identified during the initial stages of functional testing.

• Better finished-product - At the core of any application, functionalities or features need to work as per the requirements. Functional testing is essential to deliver an application where all the functionalities work seamlessly as a whole.

Advantages of non-functional testing are:

• Improved performance and security - Non-functional tests deal mainly with the performance and security of the application. Repeated execution of non-functional tests aids in ironing out the inconsistencies.

• Polished user experience - Many other aspects are involved in delivering a good user experience than just the functionalities that work. Apart from the functionalities, everything else that contributes to a better user experience, such as performance, reliability, and security, are part of non-functional testing.

Challenges associated with functional and non-functional testing

Challenges associated with functional testing are:

• Functional testing only checks if the functionalities of the application work properly, whereas everything else that enables these functionalities are tested in non-functional testing.

• Early bug detection during functional tests, and their resolution at the beginning, are critical rather than during the production phase.

• Handling bugs in the functionality testing phase must also take into account the dependencies across multiple other functionalities. In certain cases, regression testing needs to be performed for the entire application.

Challenges associated with non-functional testing are:

• Repeated testing is required to identify the actual error, especially in a large scale application where huge number of users access the application simultaneously. If not planned properly, repetitive testing could lead to increased workload for the teams.

• Unlike functional testing where a limited bandwidth of the servers is used for testing the functionalities, in non-functional testing, the servers have to be accessed multiple times which requires a considerable amount of resources. Taking up resources and time might affect productivity.

Tips for an optimized testing phase

Beyond the understanding of all the tests in functional and non-functional testing, incorporating the following aspects can be paramount to the success of the STLC:

• Requirement planning - Analyzing the requirement and planning out the order of execution for the relevant tests is mandatory if the focus is to save time and resources.

• Bug reports - Detailed reports of errors found during the testing can make it easier for the teams to work effectively and swiftly on the specific bugs.

• Flexibility - As the testing progresses, there is a high possibility that testing deviates from the actual requirement that was planned at the beginning of the STLC. In such scenarios, the team needs to adapt to the issues at hand and make optimal changes.

• Communication - Application development is generally unpredictable when there are multiple changes, the teams need to communicate with each other to discuss and iron out the issues in the STLC.

• Choosing the right tools - The right test automation tool will make it easy for the QA team to accommodate changes and execute different tests with ease. It can also enable the respective teams to communicate effectively with each other.

Zoho QEngine for testing

A comprehensive test automation software can make testing easy for all the teams working on the application and contribute towards increased productivity. Zoho QEngine is one such software which supports:

• Test case creation - Zoho QEngine offers the flexibility to create test cases in three different ways—no-code, low-code, and pro-code.

• Test case management - Zoho QEngine gives you the ability to neatly catalogue test cases based on the functionalities to be easily accessed inside test plans and test suites.

• Test case execution - Schedule automation of test cases at a select time and across different environments based on the project's requirements.

• Test reports - Analyze all the test case executions across different platforms to unveil the bugs and to share detailed reports.
• Collaboration - Comprehensive reports for the test projects on QEngine aid in collaboration with all the teams.