What is the difference between Severity and Priority?

What is the difference between Severity and Priority? Or Interviewer can ask, how to decide priority and severity of a defect?

Any defects(bugs) categorised based on these two factors called severity and priority.

Severity :-

We can understand in such way, Severity means the gravity of an undesirable occurrence or we can say how severe it is affecting the functionality. Given below types of severity and their definitions.

  • Critical: The defect that results in the termination of the complete system or one or more component of the system and cannot able to test application further and causes extensive corruption of the data. Example Segmentation Fault
  • Major: The defect that results in the termination of the complete system or one or more component of the system and causes extensive corruption of the data. The failed function is unusable but there exists an acceptable alternative method to achieve the required results then the severity will be stated as major.
  • Moderate: The defect that does not result in the termination, but causes the system to produce incorrect, incomplete or inconsistent results then the severity will be stated as moderate.
  • Minor: The defect that does not result in the termination and does not damage the usability of the system and the desired results can be easily obtained by working around the defects then the severity is stated as minor.
  • Cosmetic: The defect that is related to the enhancement of the system where the changes are related to the look and field of the application then the severity is stated as cosmetic.
Priority :-

Priority means how fast it has to be fixed. Priority is related to scheduling to resolve the problem. Or we can understand in such way, Priority means how urgently the issue can be fixed.High priority bug must fix ASAP. Given below types of priority and their definitions.

  • Low: The defect is an irritant which should be repaired, but repair can be deferred until after more serious defect have been fixed.
  • Medium: The defect should be resolved in the normal course of development activities. It can wait until a new build or version is created.
  • High: The defect must be resolved as soon as possible because the defect is affecting the application or the product severely. The system cannot be used until the  repair has been done.
Now we will see some example combination of Priority & Severity .
High Priority & High Severity:

The bug due to which tester is not able to continue to test software means Blocker Bugs like segmentation fault, any run time error.

High Priority & Low Severity:

Take an example some performance counter not updating due to which, we can not calculate our software performance. This is surely a High Priority issue. In terms of functionality it is not breaking anything so we can mark as Low Severity, but making bad impact on the reputation of software. So it highest priority to fix this.

Low Priority & High Severity:

System is crashing in the one of the corner scenario, it is impacting major functionality of system so the Severity of the defect is high but as it is corner scenario so most of functionality is not touching this corner case.

Low Priority & Low Severity:

We can take an example like, Some spelling mistake in logging.

 

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