Have you encountered new bugs in tested and delivered features while testing for later releases? Have you observed bug fixes breaking existing features or introducing new bugs? If you are a seasoned tester, the chances are you would have faced these (many times).
Everyone worth their salt in the software industry knows that discovering new bugs late in the project lifecycle can be detrimental to project success.
The purpose of regression testing is to minimize the odds of the project landing in this situation. This post aims to get you up to speed with regression testing — what, why, and how to get it right.
What is Regression Testing?
Regression testing ensures that code modifications (e.g., bug fixes, optimization) and new code added to a project do not break existing functionalities and reliability. Breaks in existing functionalities and reintroduction of old bugs are termed “regression.”
Regression testing is different from retesting. Retesting refers to running relevant test cases again to verify that a bug has been fixed. Regression testing employs a broad test suite to ensure that code changes haven’t introduced unanticipated bugs.
Regression Testing Strategies and Techniques
It’s best to carry out regression testing at all levels of the testing pyramid — unit testing, integration testing, and end-to-end (product) testing.
Unit testing is carried out by developers to verify that the portion of code (e.g., a function) they have written fulfills all the requirements. Unit tests should include both positive and negative test cases.
To address regression, the developer should carefully identify all the functions of code that may be impacted by their modified or newly added code. They should then add a few critical test cases (from the full test suite) dependent on the impacted code blocks to their unit test cases.
Integration tests validate that the various components of the application, like databases and services, communicate and coordinate with each other correctly. Integration tests invoke the components’ APIs and do not involve GUIs.
End-to-end tests simulate the product's usage by the end user through the UI. They exercise all the components needed to make the product work on the field.
Integration and end-to-end tests are difficult to implement, time-consuming to run, and demanding in resources. So, a subset of the full test suite is carefully selected for regression testing based on the test case priority. Test case priority can be evaluated on factors like the criticality of the functionalities tested and bug detection capability.
Sometimes, the full test suite is run to check for regression. This helps prevent surprises in the later stages of the project or ensure that the software is production-ready. But it is expensive to implement.
It’s helpful to run regression tests frequently. Nightly and weekly runs are common. Regression tests are integral to agile projects that stress frequent releases and continuous integration / continuous deployment (CI/CD).
How Does Regression Testing Help?
Regression testing ensures that bugs are detected as early as possible in the SDLC. Bugs become increasingly difficult and time-consuming to find the root cause and fix when spotted late after their introduction into the code.
Last-minute discovery of bugs also causes a lot of anxiety at all levels of the project team and often leads to heartburn and friction between developers and testers. It places the project in a high-risk zone of schedule slippage, cost overrun, and customer and employee dissatisfaction.
Though it may initially seem like an unnecessary overhead on time and resources, the benefits of regression testing are well worth the investment in most cases.
Characteristics of Good Regression Testing
A good regression test plan and test suite has the following features.
Span
Regression testing should span the entire project lifecycle, right from the initial stages. Regression testing should be performed at all levels of the testing pyramid.
Coverage
The regression test cases should have a broad coverage of the product functionalities. It should mandatorily cover high-priority tests and the most critical bugs identified. It should also cover all supported technologies and devices (web, desktop, mobile, different browsers, and OSes).
Frequency
Regression tests should be run at specified intervals. It is common to run regression tests every night or every week, depending on the project's size and complexity.
Automation
It is extremely difficult, if not impossible, to achieve the above requirements in large projects without test automation. Many tools and frameworks are available for automating test execution and reporting. It is best to use test automation along with version control systems (like Git) and continuous integration systems (like Jenkins).
Challenges in Automation of Regression Testing
Testing automation for web, desktop, and mobile apps involves several challenges.
Test cases are hard to write and maintain
Many tests that are easy and intuitive to perform manually are complex to describe in a computer language. Many fine details which are easy to overlook need to be taken care of during coding. It takes a good amount of time and effort to write clean, bug-free test code that works as expected.
The test code needs to be updated whenever there are changes in the UI, API, or product functionality. Maintenance pains grow if the tester updating the code differs from the one who wrote it.
Test scripts don’t work out of the box across different technologies. For example, a script written for a web application may need to be modified to test on different browsers.
Testers with programming knowledge are needed
Automation needs test engineers with expertise in programming. Automation engineers who understand the domain are scarce and more expensive than manual business testers.
Flaky tests
Automated tests can be flaky, throwing up different, unpredictable results for the same test case in different runs without any code change.
The test code needs to be updated whenever there is a change in the UI. The test results are unpredictable if this is missed.
Another cause for flakiness is the lack of synchronization between test execution and application readiness. For example, the test script may perform an action on an element before the application is ready or the element has appeared. Sometimes, an external application may not be available during test execution, leading to unstable outcomes.
Data Management
Data preparation and management is a key part of app testing. For example, the username and password need to be created before testing logins. An item may get exhausted after repeated tests involving it. It then needs to be restocked before subsequent tests. The automation script should be robust to handle such cases. Otherwise, a lot of time will be wasted on futile test runs.
Sahi Pro Solves All Your Automation Worries
Sahi Pro is an automation platform developed to solve the pain points of the QA community. Sahi Pro makes automation easy, reliable, and powerful.
- Sahi Pro Flowcharts enables business testers to automate easily without writing any code
- Built-in features (smart object identification and automatic waits) for reliable, non-flaky execution
- Capable of automating different types of applications: Web, Web Services, Windows, Java, SAP, and Mobile (both Android and iOS) applications.
- Supports fast, parallel execution on a single machine or multiple machines
- Comprehensive and detailed reports
- Easy integration to continuous integration platforms (like Jenkins, AWS)
- Includes advanced features for data management
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Summing Up
Regression testing is crucial to avoiding last-minute surprises in software projects. It holds additional significance in agile projects with frequent releases and CI/CD strategies. Automation of regression testing is inevitable for the success of large and time-critical projects. Selecting an automation tool with the right set of features goes a long way in taking the stress out of regression testing.
