In a nutshell: Functional testing, validation testing, and non-regression testing are often confused. Functional testing verifies that a feature meets a specific need; validation testing confirms that the product satisfies the end user; non-regression testing ensures that a change hasn’t broken anything. This guide clarifies their roles, their differences, and how to combine them for a comprehensive testing strategy.
With a variety of terms describing testing methodologies that aim to be clear but often fall short, testing terminology can sometimes be confusing.
In this article, we'll clarify the differences between validation functional tests and non-regression testing (NRT), but first we must note that the term “regression testing” is often used interchangeably.
In other words: regression testing = non-regression testing
The ISTQB prefers the term “regression testing,” but many people in the field also use the term “non-regression testing” (at least in France).
However, before discussing the differences between functional validation tests and non-regression tests, let’s first take a look at what they are.
What are functional validation tests?
Functional validation testing is a type of testing performed to verify that each function or feature of a software application works in accordance with the requirements specification.
The tester is not concerned with the underlying code.Functional validation tests focus on the mechanical flow oron verifying that each module is working properly.
It is carried out using test cases that recreate all possible scenarios, both negative and positive. Ideally,functional validation tests begin at the initial stage of product developmentand verify:
- Missing Features
- Incorrect specifications
- If interface errors persist
- Gaps that exist during the requirements phase
Properly executed functional validation tests ensure the delivery of a high-quality product.They help produce a bug-free product or software to ensure end-user satisfaction.
Examples of validation functional tests:
- Verify that the "Back" button on the page navigates to the correct page
- Check that the links lead to the correct pages.
- Drop-down menus must display the correct values when clicked
- Check that the "Next" button takes you to the next page
- Verify that a user can enter characters into the text fields as defined in the data elements sheet.
*Unlike regression testing, the terms“functional validation testing” and “non-functional testing” 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 the system’s performance under such conditions.
What is a regression/non-regression test (TNR)?
Regression: a process that leads back to an earlier stage.
Regression tests are performed to detect any regression in a feature that has already been tested.
These regressions in the code can occur as a result of “bug fixes,” “new features added to the code,” or “changes in requirements.”
The goal is to test all the code that might be affected by recent changes to ensure that no new bugs are introduced.
In summary, a regression test is used to verify that changes made to the software, website, or mobile app—such as the addition of a new feature or an update—have not affected existing functionality.
The differences between these two types of tests
Objectives
The purpose of functional validation testing is to determine the extent to which the developed application meets the desired requirements.
The purpose of regression testing is to verify that any changes to the application or systems have not caused any code breaks and that the system is functioning properly.
Test case executed
Functional validation tests help identify all test cases and features that have never been tested or executed before. Test cases are rerun when a defect is identified in relation to a requirement. The defect is then corrected and scheduled for retesting. During the retest, if the defect has been resolved, the related test cases that previously failed will pass.
The regression suite contains test cases that have been previously tested and resolved. Essentially , in regression testing, test cases are run to ensure that the changes have not affected previously tested functionality.
Functional validation tests are required:
- When a new system is being tested.
- When an application is verified against its specifications and the desired requirements.
- To verify that the system and module are integrated correctly.
- When the functionality of a system as a whole needs to be examined.
- To determine a system's workflow and functions.
- To ensure that the flow produces the expected result.
Regression tests are performed when:
- The customer submits a change request, which results in a change to the code base.
- The back-end code is being migrated to another platform.
- A new feature is being added to the existing app.
- Corrections have been added.
- There has been a change in the test environment.
- Critical bugs found by the tester during the testing phase are fixed by the developer.
- The developers have resolved the main issues related to performance problems and crashes.
- The app's user interface has been updated to provide a better user experience.
Process Used
The functional testing process begins with testers reading and understanding the requirements, which raises an issue if there is a discrepancy in the requirement, followed by the identification of the test input. The testers then feed the input values into the systems and compare the output with the expected results.
If the result does not match, the error is reported and the test case is marked as having failed.
The entire functional testing process includes:
- Identifying the features to be tested
- The increase in demand for data
- Executing Test Cases
- Comparing an actual result with an expected result.
- The test case failed because it did not meet the requirement.
- Creating test scenarios based on requirements
- Converting Test Scenarios into Test Cases
- Report defects and assign them to the developer if any issues are found in the application.
- Re-execute the failure scenario once the reported defect has been corrected
On the contrary, the regression testing process is entirely different, as this activity takes place only when the existing application is modified or new features are added to it.
The activities involved in this type of test are as follows:
- Identification of Modified Parts
- Prioritizing test cases based on the level of risk involved.
- Selection of test cases based on the areas affected by the change.
Feasibility of Automation
Functional validation tests are initially performed manually. Once a feature is stable, the test cases are automated.
In regression testing, test cases can be run manually or automatically. Since test cases are already stable by default (because they have already passed functional testing) in regression testing, they can be automated.
Functional test cases do not require many changes because there are fewer of them and they focus on a specific feature.
In regression testing, however, test scripts require more maintenance and may contain older test cases.
Test cases may include features that have changed, new features that have been added, or features 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 does what it is supposed to do; non-regression testing verifies that existing features still work after a change. One validates the new features, while the other protects the existing ones.
What is a validation test?
This is the test that confirms that the product meets the end user’s needs and expectations, often at the end of the development cycle before going into production. It validates “the right product,” whereas functional testing validates “the product that is built correctly.”
Are these tests complementary?
Yes. A solid strategy combines functional testing (the feature works), validation testing (it meets the requirement), and non-regression testing (nothing has been broken). These three cover different risks.