What is Regression Testing?
Regression testing is a software testing practice that ensures an application still functions as expected after any code changes, updates, or improvements.
Regression testing is responsible for the overall stability and functionality of the existing features. Whenever a new modification is added to the code, regression testing is applied to guarantee that after each update, the system stays sustainable under continuous improvements.
Changes in the code may involve dependencies, defects, or malfunctions. Regression testing targets to mitigate these risks, so that the previously developed and tested code remains operational after new changes.
Generally, an application goes through multiple tests before the changes are integrated into the main development branch. Regression testing is the final step, as it verifies the product behaviors as a whole.
Example: Think of regression testing as testing your food as you cook it and adding ingredients according to a recipe.
As you cook your food, the dish will change based on a whole host of different factors. If you add seasonings then the flavor of that dish will shift.
This would be a regression. The same holds true for software.
Difference between Regression Testing and Retesting
Are you confused between retesting and regression? The fact is that both are entirely different.
While Regression testing ensures that any update made on the code does not affect the existing functionality, whereas Retesting is carried out when test cases find some defects in the code and when those defects are fixed, the tests are done again to check whether the issues are resolved.
Retesting is to ensure whether the defects are resolved, whereas regression testing detects probable defects caused because of the changes done in the code.
Example: if we bring it back to the cooking food example, retesting might be, the process of checking the temperature of the dish. Nothing has fundamentally changed with the recipe or cooking procedure at this stage so we aren’t performing any kind of regression.
On the other hand, if we’ve now added in some new seasonings, a regression test will let us know if the taste of the dish changed or not.
Benefits of Regression Testing
While the basic aim behind conducting regression testing is to identify bugs that might have got developed due to the changes introduced, conducting this test benefits in a number of ways such as:
- Increase chances of detecting bugs caused due to new changes introduced in the software
- Helps in identifying undesirable side effects that might have been caused due to a new operating environment
- Ensures better performing software due to early identification of bugs and errors
- Highly beneficial in situations when continuous changes are introduced in the product
- Helps in maintaining high product quality
Need Of Regression Testing
This testing is required when there is any:
- Change in requirements and code is modified as per the changed requirements
- Added new features in the product
- Bug fixing
- Fixing of performance-related issues
Types of Regression Testing
Corrective regression testing is used when there are no changes introduced in the existing software/application/product specification. The existing test cases can be used to conduct the desired test.
This testing is used in situations when the modifications are added in the specifications of the product and new test cases are designed. Progressive regression testing works effectively when there are changes done in the software/application specifications as well as new test cases are designed.
We utilize a subset of the current experiments to cut down the retesting cost and effort in selective regression testing. In this case, if any changes are done to any part or module of software application/product, e.g. capacities, factors and so on and afterwards a test case must be re-executed. Here is the difficult part to determine the conditions between an experiment and the program elements it covers. It is done to observe the effect of new code development on the existing code of the application. When this type of relapse testing is directed, a subset from existing experiments is utilized, to reduce the effort needed for retesting.
The retest-all strategy is very time taking because in this testing we reuse all tests which result in the execution of avoidable test cases. This strategy is not much useful when any small modification or change is done to the application. The retest-all strategy involves the testing of all aspects of a particular application as well as reusing all test cases even where the changes have not been made. This testing is not advisable when there is a small change in the existing code.
Complete regression testing is very useful when multiple changes have been done in the existing code. This testing is specially used when multiple new changes have a certain impact on the software’s root code. Performing this testing is highly valuable to identify unexpected bugs.
Can Regression Testing Be Done Manually?
Regression testing can be performed manually. But this leads to inefficiency if the application is large and the impact is big. Also, it is very boring to execute repetitive test cases again and again for a test engineer.
To perform regression testing, the tester needs to identify the test cases which must be executed. If the number is big, testers need to find out the best combination and optimize them.
How to Perform Regression Testing
Regression testing practices vary among organizations. However, there are a few basic steps:
- Detect Changes in the Source Code
- Prioritize Those Changes and Product Requirements
- Determine Entry Point and Entry Criteria
- Determine Exit Point
- Schedule Tests
Detect the modification and optimization in the source code; then identify the components or modules that were changed, as well as their impacts on the existing features.
Next, prioritize these modifications and product requirements to streamline the testing process with the corresponding test cases and testing tools.
Ensure whether your application meets the preset eligibility before the regression test execution.
Determine an exit or final point for the required eligibility or minimum conditions set in step three.
Finally, identify all test components and schedule the appropriate time to execute.
What are the Techniques of Regression Testing?
Continuous software maintenance includes a lot of activities such as enhancements, error corrections, optimization etc. Due to these new changes, the system may start to work incorrectly. In this case, regression testing is required to handle newly generated issues. this testing can be performed using the following techniques:
- Retest all
- Regression Test Selections
- Test Case Prioritization
In Retest all you have to rerun all the test cases in your test suite. This technique is more expensive and more time consuming as compared to other techniques of regression testing.
Keeping in mind the code change in the module, in Test selection technique you have to select test cases from your test suits that you have to carry out your regression testing on.
Based on the importance of functionalities, you need to prioritize the test cases into the top, medium and low priority. These test cases are then run based on priority.
It is a mixture of Test case Prioritization and Regression test selection.
Best Regression Testing Tools
There are many regression testing tools available that could help in the execution of tests in this testing and reduce the execution time and cost. Below is the list of most important regression testing tools that can be used for both functional and regression testing:
- Ranorex Studio
- AdventNet QEngine
- Regression Tester
- IBM Rational Functional Tester
To read about them in detail click here!