Smoke Testing vs Regression Testing: A Detailed Comparison

“Never allow the same bug to bite you twice.” – Steve Maguire

The bug only won’t bite you when your code is tested effectively. Software testing aims to increase the quality of the code/software. This can be done by identifying the flaws in the code and reducing/eliminating them. By doing so developers are making the software cost-effective, enhancing the performance, ease of adding new features, and assuring customer satisfaction.

This makes software testing crucial in the software development life cycle (SDLC) as any undetected error/bug in code can cause catastrophic consequences at any stage of SDLC.

There are various types of testing including unit testing, integration testing, system testing, functional testing, acceptance testing, smoke testing, regression testing, performance testing, security testing, user acceptance testing, end-to-end testing, and more.

In this blog, we will understand the key difference between regression testing vs smoke testing. But first let us understand both types of testing individually (meaning, features, pros, cons, etc.)

What is Smoke Testing?

Smoke testing is a software testing process/type of software testing. It is also known as “Build Verification Testing”, “Confidence Testing”, and “Build Acceptance Testing”.

First used in the hardware testing procedure, Smoke testing is preliminary, non-exhaustive, initial white box testing performed at beginning of the development process/initial stages of the software development life cycle (SDLC) post-software build to identify the stability/working of most critical functions/core of the software. It is like the smoke test in Hardware Testing which involves seeing the hardware functionality by looking for smoke upon switching on the hardware component.

It is a subset of acceptance testing which enables the developers to identify the blocker bug (blocker is the severity of the bug’s impact on the application) at the early stage of the software development.

It is a type of shallow and wide testing used by a developer to declare the software build good to go for further detailed testing and also give them the ability to ship new code confidence. With the completion of the major functionality’s rapid test, the QA can further proceed to Sanity Testing or Regression Testing.

Smoke Testing Execution

As seen in the above image, after the deployment of the build in the QA environment by the development team, the build is passed for an initial smoke test by QA who starts executing the test cases on it. The test cases are prioritized base on the software’s critical functionalities. The software is then tested for created tests.

If the build passes the smoke test, it further proceeds for functional and regression testing. However, if it fails, the build is sent back to the development team for resolving the issue.

Types of Smoke Testing Methods:

• Manual Testing
• Automated Testing
• Hybrid Testing

The types of smoke testing are categorized into Formal Testing and Informal Testing.

Features

• Does not require to design of test cases
• Documented or scripted
• Verifies “stability” of the application
• Shallow and wide
• Performed manually or automatically

Advantages of Smoke Testing

• Helps to find show-stopping bugs in the early stage of testing
• Less number of test cases required
• Requires less time to execute smoke testing
• Ensures the previous build does not impact the app’s major functionalities
• Helps improve overall app quality
• The developer can execute the test eliminating the need for a QA team
• Reduces the risk of app failure
• Reduces the possibility of integrations-related threats

Limitations of Smoke Testing

• Does not cover the detailed testing of all functionalities(core functionalities only)
• Not being able to find minor issues due to the minimum number of test cases
• Requirement of a special team for proper documentation
• Manual smoke testing consumes a lot of time
• Smoke testing is no substitute to complete functional testing

Tools used for Smoke Testing:

• Selenium
• PhantomJS

Good Read: 25 Popular Software Testing Tools To Look For In 2023

Now that we have a brief about smoke testing, Let us understand more about Regression testing to get a better idea of smoke test vs regression test.

What is Regression Testing?

Also known as Verification Method, Regression Testing is a type of software testing that is conducted when code is changed, revised, updated, improved, or optimized and the developer wants to ensure the code change does not negatively impact the existing functionalities of the system or the proper working of the product.

The word ‘Regress” itself means “return to a former or less developed state”.

It is done by re-executing test cases or re-running non-functional and functional tests to keep a check on the quality of outputs. This is the reason why it is often misunderstood as re-testing but it is not as it is a black-box testing technique.

In a nutshell, developers fear the unexpected consequences of small tweaks in the software code, Regression tests saved the existing functionalities from being impacted by these small tweaks in code.

Regression Testing Process

As you can observe in the above flowchart, the process of Regression testing starts when the developers come across a bug in the code. The bug may be introduced when the developers make any changes/new versions (add new functionality, optimization, error corrections, deletion of existing features, or any such software maintenance activities) in the source code.

After changing the source code, when the program fails, this is where the Regression testing process starts. The code is debugged to find out the bug which resulted in the failure of code execution.

Required modifications are made to resolve the detected bug. Further test cases are selected from the existing one which covers the source code-modified module. If the team finds a requirement for any new test cases they can generate new ones and execute the selected test cases for the regression testing of the module.

To select the test cases for regression testing, the following techniques can be used:

• Selection of all test cases
• Selection of test cases randomly
• Selection of modification traversing test cases
• Selection of higher-priority test cases

Features of Regression Testing

• Makes development time and cost-effective
• Test cases are mainly automated
• Parallel Multiple Test Execution

Advantages of Regression Testing

• Increases the product’s quality
• Keeps existing functionalities safe from impact from any bug due to changes or updates
• Ensures no reoccurrence of resolved issues
• Helps developers maintain software stability
• Facilitates efficient software development process
• Ensures code compatibility and functionality simultaneously

Limitations of Regression Testing

• Manual Regression Testing execution is tedious and time-consuming
• Has a huge number of test cases
• The regression test is executed after every modification or new build
• As the software ages, regression suite size increases exponentially
• Test execution is resource intensive

Types of Regression Testing

• Corrective Regression Testing
• Selective Regression Testing
• Progressive Regression Testing
• Retest-all Regression Testing
• Unit Regression Testing
• Complete Regression Testing
• Partial Regression Testing

All these are different types/forms of regression testing that are best fitted for various distinctive testing scenarios/specific code updates and testers’ requirements.

Regression Testing tools

• Selenium
• WATIR
• IBM Rational Functional Tester
• Rainforest QA
• Sahi Pro
• Silktest
• TestDrive

And the list continues. You can find the tool for testing according to your testing requirement and other personal preferences.

The above brief introductions about both testing types will assist you to understand the comparison of smoke vs regression testing in detail.

To summarize it all here are regression testing vs smoke testing comparison tables to provide you with all the key differentiators in a concise form.

Smoke Testing vs Regression Testing: Comparision Table