7 Types of Regression Testing Methods You Should Know

It is common for companies to introduce minor changes from time to time in their products.
However, introducing these changes affect the application in numerous ways such as its functionality, performance, bugs, etc.
Therefore, it is important to keep the testing process on whether the software is present in the market or a small change has been introduced.
Conducting this type of testing is known as regression testing.

What is Regression Testing?

Regression testing is a technique that is carried out by implementing units of code repeatedly so as to ensure that the constant code modifications are not impacting the system’s functionality.

These modifications can be done in numerous forms such as bug fixes, functionality, integrations, patches, etc.
While, there are many software developers who strongly believe that there is no need to retest a product unless there are some complications arising in its functionality, but that does not hold true in all cases.
Conducting regression testing can act as a real blessing as there are no chances of facing unexpected surprises.

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

Types of Regression Testing

There are a number of ways in which this testing can be done. However, this depends on factors such as the type of changes introduced, bugs fixed, etc.
Some of the common types of regression testing include:
1) Corrective Regression Testing:
This type of testing is used when there are no changes introduced in the product’s specification. Moreover, the already existing test cases can be easily reused to conduct the desired test.
2) Retest-all Regression Testing:
This type of testing is very tedious and tends to waste a lot of time.
The strategy involves the testing of all aspects of a particular product as well as reusing all test cases even where the changes/modifications have not been made.
This type of testing is not at all advisable when there is a small change, that has been introduced in the existing product.

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3) Selective Regression Testing:
It is done to analyze the impact of new code added to the already existing code of the software.
When this type of regression testing is conducted, a subset from the existing test cases is used, to reduce the effort required for retesting and the cost involved.
For example, a test unit is re-run in case there is some change incorporated in the program entities such as functions and variables.
4)Progressive Regression Testing:
This type of regression testing works effectively when there are certain changes done in the program specifications as well as new test cases are designed.
Conducting this testing helps in ensuring that, there are no features that exist in the previous version that has been compromised in the new and updated version.
5) Complete Regression Testing:
Complete regression testing is the best to be used in case there are multiple changes that have been done to the already existing code.
Moreover, this type of testing is specifically used when the new change has a certain impact on the root code of the software.
Conducting this type of testing is highly beneficial to identify unexpected issues.
Once this testing is completed, the final system can be made available to the user.
6) Partial Regression Testing
Partial regression testing is done to test issues when new codes are added to already existing code.
The idea behind partial regression testing to make sure that a system is performing as it is supposed to be after addition of new code.
7) Unit Regression Testing
it’s the most important part of unit testing. Mostly conducted in isolation, mainly focused on code unit and all the dependencies and interactions are will be blocked at the time of test.

It is important to make sure that the type of regression testing that needs to be conducted is selected appropriately.
This depends on various factors such as areas of recurrent defects, the criticality of the features, etc.
But, what remains on the priority is ensuring that the software delivers the best functionality and proves to be a beneficial addition to the industry.

Importance of Regression Testing

In such a dynamic software field and heaving AGILE methodology; you will have to constantly upgrade your product to meet the latest demands of the users.
To assure that these changes do not affect the existing working of your software, it becomes mandatory to carry out regression testing.
Regression testing can help you eliminate a lot of threats that are linked with software updates.

When to carry out Regression Testing?

You can conduct this testing at any level of testing be it Unit, Integration, System, or Acceptance, but it is more appropriate to conduct it during system testing.

The Extent of Regression Testing.

Should you rerun the test cases on the full code?
Though a full regression test is desirable, but it does take a lot of time. And when you are short of time, it is suggested to do an impact analysis of the changes.
Recognize the area that has the highest probability of being affected by the changes. And you can then conduct your regression tests for that particular code.

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.

Challenges of Regression Testing

• Regression testing forms an important phase of STLC but brings along several challenges for the testers.
• Takes a lot of time: it is time-consuming, it requires rerunning a complete set of test case again for a complete or some particular set of code.
• Complex: Updates makes your code more complex, they even increase the set of test cases for regression testing.
• Communicating Business Value: Regression testing ensures that updates bring no flaws in the existing code.  But considering the time taken to complete regression testing, it becomes hard to make non-technical clients understand the value of regression testing.

Best practices of Regression Testing

While you carry out this testing, the following best practices can help you get the best results:
Are you updating your regression testing test pack regularly?
Regression test pack is a set of regression test cases build keeping in mind the older version and their functionalities.
With each new update, few new test cases are added. To avoid any future delays and rework, always keep your regression test cases pack updated.

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Are you focussing on Main Features?                                   
Your code comprises certain functionalities that are most used by the end customer.
Identify these core functionalities and make sure that your regression test pack includes test cases for these functionalities.
Are you focussing on successful Test Cases?
Make sure you include the test cases that have previously found bugs and defects in code.
Automate:
Automating regression testing is one of the best practices in regression testing as it frees the testers of the boredom of carrying out the same test cases again and again.

 How to choose Test cases?

Choosing the most apt test cases in regression testing is very important.
Test cases in this testing keep growing with the evolution in software.
The increased number of test cases results in cost and time increment to accomplish the complete set of tests.
With regression tests minimization, selection and prioritization, you can effectively reduce the size of the test set while retaining the value of regression testing.
Test cases minimization eliminates redundant test cases to reduce the number of test cases.
Test case selection identifies the test cases having relevance to recent changes.

In Test Case prioritization, order test cases in a way to maximize early fault detection.
You can select your test cases based on the following conditions:

• Frequently used Functionalities.
• Test cases for the module that is changed.
• Compound test cases.
• Test cases covering major components.
• Test cases testing core functionality.
• Successful test cases which have discovered the defects.
• Regression Testing Techniques

You can carry out this testing as per your requirements. Here are the various techniques you can leverage for regression testing.

• Retest all
• Test Selection
• Test case Prioritization
• Hybrid

#1) Retest all:
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.
#2) Regression Test Selections:
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.
#3) Test Case Prioritization:
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.
#4) Hybrid:
It is a mixture of Test case Prioritization and Regression test selection.

How to Perform Regression Testing?

The scope of this testing keeps increasing with the addition of new functionalities and changes in the code.
Keeping in the mind the scope of regression testing testers prefer to use automated tools for regression testing. But you can also carry it out manually.

Steps to follow while performing this testing.

• Recalling the above discussion–“How to choose test cases”, prepare a test suit for your regression testing.
• You can choose to automate these test cases.
• Keep updating your regression test suit, as and when required.
• Execute regression test suit, whenever there is any code change, bug detection, functionality update or whenever a situation arises to retest your code.
• Make a test report with the proper status reporting.

Tools For Regression Testing

1) Ranorex Studio
2) SahiPro
3) Selenium
4) Watir
5) TestComplete
6) IBM Rational Functional Tester
7) TimeShiftX
8) TestDrive
9) AdventNet QEngine
10) TestingWhiz
11) WebKing
12) Regression tester
13) silktest
14) Serenity
15) QA wizard
To read about them in detail click here!