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Regression Testing at a glance

Few days back some of my friend asked for more details o regression testing Regression testing is any type of software testing that seeks to uncover software errors by partially retesting a modified program. The intent of regression testing is to assure that a bug fix has been successfully corrected based on the error that was found, while providing a general assurance that no other errors were introduced in the process of fixing the original problem. Regression is commonly used to efficiently test bug fixes by systematically selecting
the appropriate minimum test suite needed to adequately cover the affected software code/requirements
change. Common methods of regression testing include rerunning previously run tests and checking whether
previously fixed faults have re-emerged.

so bottom line is if due to any code got change or introduced into the exiting program.... there is always a
chance that a bug may introduced into the system. adding new feature (changing code or adding extra system) is termed as regression. hence Regression testing is the process of testing changes to computer programs to make sure that the older programming still works with the new changes

The selective retesting of a software system that has been modified to ensure that any bugs have been fixed
and that no other previously working functions have failed as a result of the reparations and that newly
added features have not created problems with previous versions of the software. Also referred to as
verification testing, regression testing is initiated after a programmer has attempted to fix a recognized
problem or has added source code to a program that may have inadvertently introduced errors. It is a quality
control measure to ensure that the newly modified code still complies with its specified requirements and
that unmodified code has not been affected by the maintenance activity.
i have gone through http://www.exforsys.com/tutorials/testing/what-is-regression-testing.html
this is a beautiful discussion regarding regression testing

What is Regression Testing?
This article attempts to take a close look at the process and techniques in Regression Testing.
What is Regression Testing?
If a piece of Software is modified for any reason testing needs to be done to ensure that it works as
specified and that it has not negatively impacted any functionality that it offered previously. This is
known as Regression Testing.
Regression Testing attempts to verify:
- That the application works as specified even after the changes/additions/modification were made to it
- The original functionality continues to work as specified even after changes/additions/modification to the software application
- The changes/additions/modification to the software application have not introduced any new bugs
When is Regression Testing necessary?
Regression Testing plays an important role in any Scenario where a change has been made to a previously tested software code. Regression Testing is hence an important aspect in various Software Methodologies where software changes enhancements occur frequently.Any Software Development Project is invariably faced with requests for changing Design, code, features or all of them.
Some Development Methodologies embrace change.
For example ?Extreme Programming? Methodology advocates applying small incremental changes to the system based on the end user feedback.Each change implies more Regression Testing needs to be done to ensure that the System meets the Project Goals.

Why is Regression Testing important?
Any Software change can cause existing functionality to break. Changes to a Software component could impact dependent Components. It is commonly observed that a Software fix could cause other bugs.
All this affects the quality and reliability of the system. Hence Regression Testing, since it aims to
verify all this, is very important.
Making Regression Testing Cost Effective:
Every time a change occurs one or more of the following scenarios may occur:
- More Functionality may be added to the system
- More complexity may be added to the system
- New bugs may be introduced
- New vulnerabilities may be introduced in the system
- System may tend to become more and more fragile with each change
After the change the new functionality may have to be tested along with all the original functionality.
With each change Regression Testing could become more and more costly.
To make the Regression Testing Cost Effective and yet ensure good coverage one or more of the following
techniques may be applied:
- Test Automation: If the Test cases are automated the test cases may be executed using scripts after each
change is introduced in the system. The execution of test cases in this way helps eliminate oversight, human
errors,. It may also result in faster and cheaper execution of Test cases. However there is cost involved in
building the scripts.
- Selective Testing: Some Teams choose execute the test cases selectively. They do not execute all the Test
Cases during the Regression Testing. They test only what they decide is relevant. This helps reduce the Testing
Time and Effort.
Regression Testing ? What to Test?
Since Regression Testing tends to verify the software application after a change has been made everything that may be impacted by the change should be tested during Regression Testing. Generally the following areas are covered during Regression Testing:
- Any functionality that was addressed by the change
- Original Functionality of the system
- Performance of the System after the change was introduced
Regression Testing ? How to Test?
Like any other Testing Regression Testing Needs proper planning.
For an Effective Regression Testing to be done the following ingredients are necessary:
- Create a Regression Test Plan: Test Plan identified Focus Areas, Strategy, Test Entry and Exit Criteria.
It can also outline Testing Prerequisites, Responsibilities, etc.
- Create Test Cases: Test Cases that cover all the necessary areas are important. They describe what to Test, Steps needed to test, Inputs and Expected Outputs. Test Cases used for Regression Testing should specifically cover the functionality addressed by the change and all components affected by the change. The Regression Test case may also include the testing of the performance of the components and the application after the change(s) were done.
- Defect Tracking: As in all other Testing Levels and Types It is important Defects are tracked systematically,
otherwise it undermines the Testing Effort.
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