In brief: Functional tests, validation tests, and non-regression tests are often confused. Functional testing verifies that a feature meets requirements; validation testing confirms that the product satisfies the end-user; non-regression testing ensures that an evolution has not introduced any regressions. This guide clarifies their roles, differences, and how to combine them for a comprehensive testing strategy.
With a variety of terms describing testing methodologies that often attempt to be explicit but frequently fail, testing terminology can sometimes be confusing.
In this article, we will clarify the differences between the functional validation tests and the non-regression tests (NRT), but we must first establish that the term 'regression tests' can be used interchangeably.
In other words: regression test = non-regression test
ISTQB prefers the term regression test, but many industry professionals also use the term non-regression test (at least in France).
However, before delving into the differences between functional validation tests and regression tests, let's first examine what they are.
What are Functional Validation Tests?
Functional validation tests are a type of testing conducted to verify that each function or feature of the software application operates in accordance with the requirements specification.
The tester is not concerned with the underlying code. Functional validation tests focus on the operational fluidity or on verifying the proper functioning of each module.
They are conducted using test cases that recreate all possible scenarios, both negative and positive. Ideally, functional validation tests commence during the initial product development phase and verify:
- Missing functionalities
- Incorrect specifications
- If interface errors persist
- Gaps existing during the requirements phase
Well-executed functional validation tests enable the delivery of a high-quality product. They contribute to producing bug-free products or software, ensuring end-user satisfaction.
Examples of Functional Validation Tests:
- Verify that the back button on the page navigates to the correct page
- Verify that links redirect to the correct pages.
- Dropdown menus should list the correct values when clicked
- Verify that the next button proceeds to the next page
- Verify that a user can enter characters into text fields as defined in the data element sheet.
*Unlike regression tests, the terms «functional validation tests» and «non-functional tests» cannot be used interchangeably. Non-functional testing involves evaluating the application based on non-functional aspects such as performance, usability, security, reliability, load, stress, etc. These tests are conducted using real-world scenarios to verify system performance when subjected to such circumstances.
What is a Regression/Non-Regression Test (RNT)?
Regression: a reversion to an earlier stage.
Regression tests are conducted to detect any regression in an already tested functionality.
These regressions in the code can occur as a result of “bug fixes,” “new features added to the code,” or “changes in requirements.”
The objective is to test all code that might be impacted by recent changes to ensure that no new bugs are introduced.
In summary, a regression test serves to verify that modifications made to the software, website, or mobile application, such as the addition of a new feature or an update, have not adversely affected existing functionalities.
The Differences Between These Two Types of Tests
Objectives
The purpose of functional validation tests is to determine to what extent the developed application meets the specified requirements.
The purpose of regression testing is to verify that any changes made to the application or systems have not introduced code breaks and that the system continues to function correctly.
Test case executed
Functional validation tests facilitate the understanding of all cases and functionalities that have not been previously tested or executed. Test cases are re-executed when a defect is identified against a requirement. Subsequently, it is corrected and assigned for retesting. During retesting, if the defect is resolved, the related test cases that previously failed are marked as passed.
The regression suite comprises cases that have been previously tested and resolved. Fundamentally, in regression testing, test cases are executed to ensure that modifications have not adversely impacted previously tested functionalities.
Functional validation tests are required when:
- A new system is being tested.
- An application is verified against its specifications and desired requirements.
- To verify that system and module integration functions correctly.
- The overall functionality of a system needs to be examined.
- To determine a system's workflow and its functions.
- To ensure the workflow yields the expected outcome.
Conversely, regression tests are performed when:
- A change request is issued by the client, leading to a modification of the codebase.
- The back-end code is migrated to another platform.
- A new feature is added to the existing application.
- Patches are implemented.
- There is a change in the testing environment.
- Critical bugs identified by the tester during the testing phase are rectified by the developer.
- Major concerns regarding performance issues and crashes are addressed by the developers.
- The application's user interface is modified for an enhanced user experience.
Process Utilized
The functional testing process commences with testers reviewing and comprehending requirements, which identifies any discrepancies in the requirements. This is followed by the identification of test inputs. Input values are then transmitted to the systems, and the output is compared against the expected results.
If the outcome does not match, the defect is reported, and the test case is marked as failed.
The entire functional testing process includes:
- Identifying the functionalities to be tested
- The increasing demand for data
- Test case execution
- Comparison of an actual result against an expected result.
- The test case failure that did not align with the requirement.
- Creating test scenarios based on requirements
- Converting test scenarios into test cases
- Logging defects and assigning them to the developer, should any discrepancies be identified within the application.
- Re-execution of the failing test case after the reported defect has been resolved
Conversely, the regression testing process is entirely different, as this activity only occurs when the existing application is modified or new functionalities are added.
The activities involved in this type of testing are as follows:
- Identification of modified components
- Prioritization of test cases based on the incurred risk.
- Selection of test cases based on the areas impacted by the modification.
Automation feasibility
Functional validation tests are initially performed manually. Once a feature is stable, the test cases are automated.
In regression testing, test cases can be executed either manually or automatically. Since test cases are inherently stable (having already passed their functional testing) in regression testing, they are suitable for automation.
Functional test cases typically require minimal modifications as they are fewer in number and focused on a specific functionality.
Conversely, in regression testing, test scripts demand more significant maintenance and may include older test cases.
Test cases may encompass functionalities that have changed, new functionalities that have been added, or certain functionalities that have been removed; therefore, the regression suite must be updated after each release.
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FAQ
What is the difference between functional testing and non-regression testing?
Functional testing verifies that a feature performs its intended function; non-regression testing ensures that existing functionalities continue to operate correctly after a modification. One validates new implementations, while the other safeguards existing ones.
What is validation testing?
This test confirms that the product meets the end-user's needs and expectations, often performed at the end of the cycle before production deployment. It validates «the right product», whereas functional testing validates «the product done right».
Are these tests complementary?
Yes. A robust strategy combines functional tests (ensuring functionality operates as intended), validation tests (confirming it meets requirements), and non-regression tests (verifying that no existing functionality has been broken). These three approaches address distinct risk profiles.
Further Reading
To see the solution in action, check out our non-regression tests.
See also: Mr Suricate Datadog vs. Contentsquare: Differences and Complementarity.
Take it a step further: automated functional testing.
