Software Testing: Severity vs. Priority

1. Introduction

As software developers, we know how important it is to ensure our programs work well and meet users’ needs. One way to do this is through software testing, which looks for defects or bugs in software before it is released.  

In this tutorial, we’ll focus on severity vs. priority in software testing. In software testing, these terms are frequently used interchangeably, but they have distinct meanings.

2. Severity vs. Priority: Definitions and Differences

Severity and priority are two terms used to describe the impact and importance of a software defect.

2.1. Severity

Severity refers to the level of impact a defect has on the software’s functionality. It measures how severe the defect is and how much it affects the software’s ability to perform its intended function.

2.2. Priority

Priority is the order in which problems should be fixed based on how much they affect the business. A defect with a high priority needs to be fixed right away, while a defect with a low priority can be fixed later. 

2.3. Differences

We need to distinguish between the two, as defects with high severity may not have high priority.

For example, a minor defect with a low severity rating may not significantly impact the software’s quality and functionality. Still, it could have a high priority rating if it affects a critical business process. On the other hand, a defect that has a high severity rating but doesn’t have a big effect on the business may have a lower priority. 

Let’s take a look at their differences:

3. Understanding Severity and Priority in Software Testing

The severity level is used to describe how a bug or defect affects the way the software works.

We can divide the severity level into four levels:

• Critical: A defect that results in the complete failure of the software system
• High: A defect that significantly affects the software’s functionality
• Medium: A defect that partially affects the software’s functionality
• Low: A defect that results in the software system’s minimal loss of functionality or inconvenience to the user

Similarly, we use the priority level to decide the order in which bugs need to be fixed based on how they affect users or the business. Priority levels can be different for each software program, and they can also be put into one of four levels:

• Critical: A defect that causes severe business impact or loss to the user, such as financial loss or damage to a company’s reputation
• High: A defect that causes significant inconvenience to the user or impacts business operations
• Medium: A defect that moderately impacts the user or the business, such as a minor inconvenience or delay
• Low: A defect that minimises impact on the user or the business

4. How to Determine Severity and Priority in Software Testing

We could use several criteria to figure out how bad or important a defect is, such as: 

1. Impact on functionality: We consider the impact of the defect on the software’s ability to perform its intended function. A defect that affects critical functionality will have a higher severity and priority rating
2. Frequency of occurrence: We consider how often the defect occurs in the software. A defect that occurs frequently will have a higher priority rating, even if its severity is low
3. Business impact: We consider the impact of the defect on the business. A defect that impacts critical business processes or results in financial loss will have a higher priority rating
4. User impact: We consider the impact of the defect on the user experience. A defect that causes significant inconvenience or frustration to the user will have a higher priority rating

By considering these criteria, we can determine the severity and priority of a defect and prioritize them accordingly. 

Now that we know about these criteria, let’s look at a flow chart of prioritizing defects based on severity and priority:

As we can see, severity is usually determined first, followed by priority. Once we determine the severity,  we’ll assign the priority based on the urgency with which the defect needs to be addressed. This allows us to ensure that critical defects are addressed first while less critical defects are addressed promptly.

5. Severity vs Priority: How They Work Together

Severity and priority are closely related in software testing but are not the same. Severity measures the technical impact, while priority measures the business impact.

We need to consider both factors to determine the severity and priority of a defect.

Let’s have a look at a few examples:

The table above shows that a high-severity bug might not have a high priority if it doesn’t affect the user or business significantly. Similarly, a low-severity defect may have a high priority if it substantially affects the user or the business.

6. Conclusion

In this tutorial, we learned about the concepts of severity and priority in software testing and defect management. It is important to consider both severity and priority when determining the order in which defects should be addressed.

Best practices for prioritizing and addressing software issues include identifying and prioritizing critical defects, maintaining a defect tracking system, and communicating the status of defects to stakeholders.