Sanity testing vs. regression testing

Software is a complex system – when changing one component or adding a new one, you can only guess how it will react. This is like Jenga. Players have to remove a block without being sure how the tower will react. The balance changes every time, so even the elements that have not been touched are affected.

Application changes can have the same impact on a system. In this case, QA specialists apply two types of checks: sanity testing and regression testing. Both types are associated with alterations in the application code, correction of defects, or changes in the test environment. What is the difference between them? What are the cases when each of them should be used? We will consider these issues in this article.

More information about sanity testing

Sanity testing is an in-depth check of functionality after minor changes in a program. This is how a software testing company tries to make sure that defects are fixed and this fixing hasn’t led to new problems.

During the process, a team focuses on testing the application’s operability rather than on detailed testing. If the check for sanity is failed, a QA specialist rejects the build to save time and money for more critical testing.

For example, there is an eCommerce application with the following modules: login page, the home page, profile page, new user creation, and so on. A defect in the login form is found – the password field accepts four characters, whereas the requirement is more than eight characters. QA specialists report this bug to programmers.

The programmers fix the defect and give the function back to testers, who check if it works properly now and if the change didn’t affect other related functions. As part of sanity testing, it is necessary to analyze the login page and profile page to make sure everything is functioning correctly in both.

Sanity testing is considered a subtype of regression testing, focuses on a smaller part of the application (particular features), and in most cases, is carried out without scenarios. This type of testing is a checkpoint to see if the testing of the build can continue.

More information about regression testing

Regression testing, like sanity testing, is aimed at checking software after any changes, updates, or improvements to the code. However, it is responsible for the overall stability of existing functions and the stability of the updated system.

The goal of regression testing is to reduce risks so that previously written and tested code remains functional after changes and the entire application behaves correctly.

The need for regression testing of software arises when:

  • a new requirement for an existing function appears;
  • additional functionality is implemented;
  • a defect in the code is fixed;
  • source code is optimized;
  • configuration is changed, and so on.

In such cases, QA engineers check all the app functions, even if only part of the code has been changed. Therefore, the edited function is, first of all, put through a sanity test, and then full regression testing of all functionality is carried out.

Regression and sanity testing: what’s the difference?

Sanity and regression testing go hand in hand, so it is difficult for nonspecialists to understand how these two types of tests differ from each other and what the benefits and challenges of using them are.

  • Area to be checked

The area of sanity testing is narrower and focused only on a particular feature and related functionality. Regression testing allows you to make sure that the entire system behaves correctly after bug fixing.

  • Place in the testing process

Sanity testing is part of regression testing and is conducted after the build is ready. Regression tests are run only when some changes become mandatory in an existing project.

  • Time

Sanity testing is usually carried out in a limited time as changes are made. The checks take around two or three days. Regression testing is planned in detail beforehand and is conducted at the end of each sprint.

  • Method of carrying out

Sanity checking is performed manually and doesn’t require writing a test scenario. Regression testing is mostly automated, but part of it is performed by a QA engineer based on the developed test cases.

  • Impact on the project budget

Since sanity testing doesn’t require a scenario, is carried out within short timeframes, and is not planned, there is no effect on the project budget. Regression testing, on the contrary, can increase the software cost due to thorough elaboration – in-depth checks of functionality, user interface, performance, browser, and so on.

To make it clearer, we’ll explain this by giving an example. Let’s say programmers are working on a fitness app that is already in stores. An update of the app is planned. When a new build is ready, the product will undergo smoke testing. QA specialists will assess whether it is possible to install the application, launch it, and log in. If these checks are passed successfully, the testers will start sanity testing to see if all the tabs are available, if video and audio can be played, if BMI and calories are calculated accurately, and so on. This is manual testing of each module’s basic functions.

Sanity testing is followed by regression testing that covers every detail of functional capabilities and a graphical interface. For example, QA engineers have to make sure that adding a barcode scanner hasn’t broken the password reset or weekly progress page layout. These checks are often automated.

Advantages and disadvantages of sanity testing

Sanity testing helps to quickly find defects in core functions when QA is limited in time, and a release must be delivered in a short time frame. There is no need to document test cases, run them, or generate reports on errors for this kind of check. If bugs are found during sanity testing, the project is deferred for revision. This approach saves time and effort in running more important regression tests.

On the other hand, sanity testing only focuses on certain limited commands and functions of the software. Checks are not scenario-based, so they are carried out at a specialist’s own discretion and without reference to the future.

Advantages and disadvantages of regression testing

Regression testing checks the entire system after a newly added function is evaluated for stability. It is intended to conduct continuous testing, which contributes to improving product quality and reliability. Revealing a defect before an application is released to production helps the team meet deadlines and deliver high-quality software.

Regression testing ensures business continuity under the conditions of rapid software changes. Automated tests save execution time so the test team can focus on performing critical checks. We have written about the benefits of automated tests before. According to research by Paul Grossman, such tests cut the cost of quality assurance services by nearly three times and improve test coverage by five times.

At the same time, regression tests should be automated wisely; otherwise, the team risks being stuck maintaining old cases at the expense of creating new ones. The main disadvantage is associated with the fact that an automated scenario will only search for defects it is programmed for, and other errors may go unnoticed. Preparing automated scripts can take a long time, depending on the project’s complexity. Automation tools need to be regularly updated, which requires time and resources. Both manual and automated regression involve explicit costs for software testing services.

Conclusion

Sanity testing and regression testing differ mainly in use and purpose. However, sanity testing can be performed instead of regression if a deadline is around the corner and product quality needs to be quickly assessed. This saves time and effort and allows one to decide upon ceasing the testing process if the software can’t pass even the sanity check.

Globally, the goal of both types of checks is to prove that the product functions correctly after changes or modifications are made. It is recommended to conduct both sanity and regression testing. You can do it in-house or tap into software testing outsourcing. This will help your company be flexible in different conditions and allocate resources more wisely.

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