Test Cases Prioritization For Regression Testing [Methods & Best Practices]

Test Cases Prioritization For Regression Testing

One of the most critical software development and maintenance aspects is regression testing. To avoid unwanted changes, a set of test cases is run whenever software is modified, and the new outputs are compared to the older ones. 

If the new and old outputs match, it means that the changes made in one part of the software do not affect the remaining software.

If changes occur, it is impractical to re-run every test case for a program. However, selecting regression test cases can be solved by prioritizing the test cases. 

For example, regression test prioritization techniques reorder the execution of a test suite to detect flaws earlier in the testing process.

Efficient regression testing is required to keep an application running perfectly after every small or significant change. And effective regression testing necessitates the careful selection of regression test cases for execution each time. 

Therefore, prioritizing test cases is crucial so that we execute test cases with the highest priority and are completed first.

The test cases for regression testing are prioritized based on the business requirements, previous test cycle experience on the functionality of existing features, and delivery timelines.

In this article, we will learn about Test Case Prioritization In Regression Testing, so read the article carefully and meet you at the conclusion.

Test Cases Prioritization For Regression Testing: Need, Best Practices & Factors to Consider

Why Do We Need To Prioritize Test Cases For Regression Testing?

  • Prioritizing test cases assists the DevOps team in lowering the cost of the software test execution phase and the time required for test execution to deliver an exceptional quality product.
  • It enables testers to consider and analyze which tests to run to manage the risks associated with software delivery.
  • Prioritization enables the team to address the most critical defects early in test development.
  • By prioritizing test cases for regression testing, the DevTestOps team can detect and correct errors as early as possible, saving time.
  • For larger projects, regression testing consumes a significant amount of time.
  • The test execution may take more than one sprint to complete in some cases.
  • This lengthens test execution time, increases individual effort, and raises project costs.
  • Furthermore, repeatedly running the same set of test cases leads to a loss of concentration.
  • The testers may fail to test the most critical application functionality, resulting in bugs being released into production.
  • This eventually raises the project’s cost.

How Should One Choose Test Cases For Regression According To Priority?

Regression testing is the last yet essential phase before software or updates are released in the market. Delays can result in negative marketing, missed deadlines, and regenerate customers. Test case prioritization in regression testing based on time and importance, on the other hand, will ensure that a test cycle is completed on time.

#01 Complex Test Cases

Many system functions rely on complex pathways involving GUI sequences. As a result, sequencing issues can arise as the system becomes more complex. As a result, complex test cases must also be covered in regression tests.

Most experts recommend using a risk-based testing approach, in which test cases are ranked based on certain factors and then prioritized. These prioritized tests save time, effort, and money.

Test Cases Are Divided Into Two Categories For Ease Of Use:

  • High priority: This category includes mission-critical functions, error-prone modules, and recently changed modules; these test cases add a lot of value to the project.
  • Medium Priority: Negative test case scenarios and complex test cases are examples of medium-priority test cases. These test cases can also have a significant impact on business value.
  • Low Priority: There are UI and other stable test cases that are low priority. These are the last items on the priority list and should only be included if necessary.

High and medium-priority test cases should be run during each regression testing sprint, while low-priority test cases should be run only once before the final release.

#02 Test Cases That Frequently Produce Bugs

During the production cycle, test cases that fail frequently can be identified. These test cases cover areas of the software that are frequently fragile and frequently fail after a change. These cases must be prioritized and incorporated into the regression test suite.

#03 Cover Field Validation Test Cases 

A selection of negative test cases covering field validations. If we fail to enter the details of a mandatory field in a form, the application displays an error message preventing the user from proceeding to the next section.

#04 Test Cases That Cover Mission-Critical Functions

The core aspects of the software can be identified based on the business requirements document. For example, make sure that the regression test includes all of the test cases that cover these core functions. A traceability matrix can also be used to gather all high-priority cases.

#05 Test Cases That Cover Frequently Changed Code Sections

Many parts of the software are updated regularly. However, these components are more prone to flaws. As a result, you should incorporate them into your regression suite. Include test cases for recently changed functionalities as well.

#06 Cases of Integration Testing

In practice, integration tests are housed in their own module. However, it is critical to include them in the regression suite as well to ensure that no last-minute changes disrupt the flow between modules.

#07 Cover End-To-End Test Flows

Here we can cover all of the end-to-end integration test cases in which the happy flows of a module are tested from start to finish.

Read also: A comprehensive and Educative Guide on Regression Testing

How Test Cases Can Be Prioritized Based On A Certain Technique

Test Case Prioritization In Regression Testing Based On Ant Colony Optimization

Test case prioritization in regression testing is an effective method for increasing the efficiency of regression testing activities. It orders a regression test suite to execute higher priority test cases before lower priority ones. The problem is determining how to optimize the test case ordering based on some criterion.

An algorithm that prioritizes test cases using ant colony optimization (ACO), taking three factors into account:

  • Several flaws were discovered.
  • Time for execution
  • The severity of the fault

These three variables are used in the ant colony optimization algorithm to help identify more severe flaws earlier in the regression testing process.

An Ontology-Based Test Case Prioritization Approach In Regression Testing

Ontology-based approaches can bring together a variety of software artifacts. They can also describe software design and testing while adhering to the complete set of semantic rules. 

For example, researchers proposed ‘ ontology-based knowledge map methodology’ to reduce the failure rate of ‘business process re-engineering. Ontologies are formal representations of various entities, their behavior, interfaces, and associations.

They are widely used to meet the needs of automation and decision-making. Prior research has focused on TCP aspects such as codes, requirements, risks, etc. However, there has been little research into identifying software system defects using test case prioritization based on ontologies.

The proposed method uses web services analysis and ontology to assess objective risk management. Furthermore, ontology-based literature has successfully classified items in various research domains.

Ontology is a rigorous and formal approach to knowledge representation that provides terms with precise and unambiguous semantics. 

Ontologies in software testing provide a shared knowledge understanding of concerned entities and their relationships, allowing the easy organization, maintenance, and updates.

Factors to be Considered for Test Case Prioritization for Regression Testing

Many factors can influence test case selection and prioritization. In our proposed algorithm, three factors are considered for prioritizing the test cases, and these factors are discussed below :

#01 A Test Case Discovered Several Flaws

A test case covers one or more flaws in its execution. For example, a test case’s fault coverage capacity indicates the number of faults it can detect. 

For example, in the test case order, the test case covering the most faults should be scheduled first.

#02 The Execution Time Of A Test Case

The time cost of a test case is essential in efficient regression testing. Time constraints on regression testing typically prevent the execution of the entire test suite. As a result, test case execution time is considered when prioritizing test cases.

#03 The Severity Of The Fault

Different faults have different effects on the same software, and the severity of the fault determines its acceptance. Therefore, the test case revealing more severe faults should be executed earlier to find more severe faults during the early testing phase.

Another factor is the fault detection rate, which measures how quickly a test case detects faults. It is calculated using the number of faults detected and the time it takes to find them for each test case.

Read also: A Guide to Automated Regression Testing Tools


Test case prioritization enables testers to categorize test cases according to their highest and lowest priority to execute tests efficiently. 

This leads to the consistent delivery of high-quality software. Users also love regular updates and proper time software delivery, which leads to a better impression in the market.

In this article, we deep dive into understanding every aspect of prioritizing regression testing; we understand Why, What, and How to prioritize regression testing. I know after this article, you will get tons of positive results, save more time, and conduct quality regression testing.

But the best way for regression testing, especially when you have a large number of regression test cases to test, is to automate them can solve a lot of problems. And if the automated test cases can be prioritized, this can result in a significant return on investment.

Automation testing tools save your time, effort, and money and provide the best ROI. 

TestGrid automation testing is the best value-for-money product in the market. Even a person with no programming knowledge can create test cases with the TestGrid automation testing tool. 

Keywords for creating and executing automation testing are required in TestGrid. TestGrid automation tool is bundled with tons of features.