Difference between Severity and Priority, Example Scenarios

The difference between Severity and Priority is explained in this article with examples. While these are simple concepts it is important to know the difference.

The following topics are covered in this article

  1. What is Severity
  2. Levels of Severity
  3. What is Priority
  4. Levels of Priority
  5. Who decides severity and priority of a defect
  6. Difference between severity and priority
  7. Scenarios with severity and priority combinations
  8. Understanding severity and priority with examples

What is Severity?

Severity is an indicator of the impact of the defect on the software. For example, let us assume you have a web application where the user clicks on a rarely used link and it crashes. Then, the defect is said to be having high severity even though the chances of the user clicking on the link is rare.Difference between severity and priority

Levels of Severity

  • Critical: If a defect causes the termination or complete shut-down of the application, then its severity is “Critical”.
  • Major: If the defect results in the termination of the system but there exists one or more alternative methods to achieve the desired results or use the system, then the defect is said to have the severity level “Major”.
  • Moderate: The severity of bug will be “Moderate” when the defect in the system does not cause the program to terminate but produces results that are not correct or inconsistent.
  • Minor: A defect is of severity “Minor” when the usability or functionality of the system is not affected much but must be fixed. The results are obtained by small corrections and there is no break-down of the system caused by the defect.
  • Cosmetic: Defects that are related to the look and feel of the system are given the severity “Cosmetic”.

What is Priority?

Priority is considered from the customers point of view. Priority indicates how soon the defect needs to be fixed by the developer. Priority is set by the product manager / customer and it determines the time frame given to the developer to fix the bug.

Levels of Priority

  • Low: A defect that can be deferred or fixed in the later stages once the higher priority ones are fixed, as it is not serious from the requirement point of view is of low priority.
  • Medium: A defect that needs to be fixed during the normal course of development activity is given the status as “Medium”. Such defects occur when a particular feature cannot be used the way it should be because of some environmental issue, defect in the program, or some code that has to be added. Usually, these defects are fixed and delivered to the testing team as a part of a new release.
  • High: Those defects that need to be fixed as soon as possible so that the testing team can continue with the testing are said to be of high priority. The core functionality fails as a result of such defects and the system cannot be tested or used until the defect is fixed.

Who decides the Severity and Priority of a Defect?

The organization decides the standards regarding who sets the priority and severity of a defect. However, in most cases, the severity type of a defect is set by the tester based on the product functionality and the written test cases. The priority is decided by the product manager based on the customer requirements.

Difference between Priority and Severity

PRIORITY SEVERITY
Priority indicates how quickly the bug should be fixed. Severity indicates the degree of impact the defect has on the functionality.
Set by the Product Manager after consulting in accordance with the requirement document. Set by the tester based on the functionality.
Priority is connected to scheduling. Severity is connected to quality standards.
The levels assigned to Priority are low, medium and high. The levels assigned to severity are critical, major, moderate, minor and cosmetic.
Severity takes into consideration the customer requirements. Severity takes into consideration the technical aspects of the application.
Subjective and changes can occur based on the project under consideration. Objective and normally does not change.
If the Priority of a defect is high and the severity is low, then, the defect must be fixed immediately. If the Severity of a defect is high and the Priority is low, then, the defect must be fixed but not immediately.

Common scenarios related to Severity and Priority

  1. Consider a defect that does not permit the tester to continue with the testing at any cost or causes the application to crash. Even the basic/main functionality does not work as expected. Such a defect is considered High Priority with High Severity.
  2. A defect that is visible to the customer but is not likely to affect the functionality of the app like an issue with the logo or a spelling mistake is considered a High Priority defect with Low Severity.
  3. A defect that causes the system to crash and makes the system unusable but happens only when user clicks on any link that are not used normally are considered as defects with High Severity but Low Priority.
  4. A cosmetic error that is not visible during normal use is considered as a Low Priority defect with Low Severity.

Understanding Severity and Priority with examples

Let us try to understand severity and priority by considering an e-commerce application like amazon.com

High Severity, Low Priority: Suppose the tester clicks on the “Privacy Notice” hyperlink at the bottom of the amazon.com home page and the page is not displayed. This defect will be of high severity because functionality is not working. The priority is low because people do not normally spend time on reading the privacy notice.

High Severity, High Priority: You login to your amazon.com account, add items to the cart and click “Proceed to Checkout” button. You make the payment and the system crashes. This defect makes the whole buying functionality unusable and so the severity is high. The basic purpose of amazon.com is to buy and sell products and most of the customers are affected by this. So, this defect is of high priority which must be fixed immediately for the buying process to work.

Low Severity, High Priority: Suppose, that in the amazon.com website, the logo is displayed as ”amazn.com” with the letter “o” missing. This defect does not affect the buying/selling or any other functionality in any way. So, the severity of this defect is low. But, a mistake in the company logo affects the brand identity and impacts the user experience. So, the defect is of high priority.

Low Severity, Low Priority: Suppose the tester clicks on the “Conditions of Use” hyperlink at the bottom of the amazon.com home page. If there is an alignment issue in the text displayed or if there is a spelling mistake in the content displayed, the defect is said to be of low priority because people rarely read this page and it does not impact user experience. The severity is also low because the functionality of the application is not affected.

Summary

Priority and Severity are two important terms that are associated with a defect that helps in the right classification of the defect. These two terms help in efficient defect tracking process and reduce the overall defect turnaround time.