Understanding Severity and Priority in Software Testing

In software testing, severity and priority are two important concepts that help manage defects and issues efficiently. Though they may sound similar, they address different aspects of a defect or bug.

Severity

Severity refers to the impact of a defect on the system's functionality. It indicates how critical the bug is and how it affects the application's performance or functionality. Severity is usually assigned by the tester and focuses on the technical aspect of the defect.

Severity Levels:

1. Critical: The defect causes a complete failure of the system, halting any further progress. It requires immediate attention and resolution.

- Example: The application crashes when a user tries to log in, preventing all users from accessing the system.

2. Major: The defect causes significant loss of functionality, but some parts of the system can still operate.

- Example: A financial application fails to calculate interest correctly, affecting all financial transactions but allowing users to access other features.

3. Moderate: The defect causes a partial loss of functionality and might affect some features but the system can still be used.

- Example: A form on the website does not save data when a user fills it out, but the rest of the site functions correctly.

4. Minor: The defect causes a small issue that does not significantly impact the system's functionality.

- Example: The alignment of text on a webpage is slightly off, but all functionality remains intact.

5. Trivial: The defect is very minor and does not affect functionality at all. These are often cosmetic issues.

- Example: A typo in the help text of the application.

Priority

Priority refers to the order in which a defect should be fixed. It indicates how soon the bug needs to be addressed based on business needs. Priority is usually assigned by the project manager or product owner and focuses on the business aspect.

Priority Levels:

1. P1(High): The defect needs to be fixed immediately. These are often tied to severe defects that affect many users or critical business functions.

- Example: An e-commerce site has a defect that prevents users from completing the checkout process.

2. P2(Medium): The defect should be fixed soon, but it is not as urgent as high-priority issues. These are important but not critical.

- Example: A search feature returns results slowly, but users can still perform other functions.

3. P3(Low): The defect can be fixed in due course. These are typically minor issues that do not significantly impact the user experience.

- Example: A logo on the site is outdated but does not affect usability or core functionality.

Examples Combining Severity and Priority

1. High Severity, High Priority:

- A banking application does not allow users to transfer funds between accounts. This is both critical (high severity) and urgent to fix (high priority) because it affects a core functionality used frequently by customers.

2. High Severity, Low Priority:

- A report generation feature for an annual audit is broken. It is critical (high severity) because it affects the accuracy of financial data, but since the audit is months away, it might have a low priority for immediate fix.

3. Low Severity, High Priority:

- A typo in the company's name on the homepage. This is a minor issue (low severity), but it might be high priority to fix quickly because it affects the company’s professional image.

4. Low Severity, Low Priority:

- A rarely used admin interface has a minor UI glitch that does not affect functionality. This issue might be addressed in the next maintenance cycle.

Tips for Determining the Severity of a Defect

• Decide the frequency of occurrence: In some cases, if the occurrence of a minor-defect is frequent in the code, it can be more severe. So from a user’s perspective, it is more serious even though it is a minor defect.
• Isolate the defect: Isolating the defect can help to find out its severity of the impact.

Understanding the distinction and interplay between severity and priority helps teams manage and resolve defects more effectively, ensuring that the most critical and business-impacting issues are addressed first.

Happy Testing!