What is Defect Density?

DEFINITION
Defect Density is the number of confirmed defects detected in software/component during a defined period of development/operation divided by the size of the software/component.

ELABORATION
The ‘defects’ are:

• confirmed and agreed upon (not just reported).
• Dropped defects are not counted.

The period might be for one of the following:

• for a duration (say, the first month, the quarter, or the year).
• for each phase of the software life cycle.
• for the whole of the software life cycle.

The size is measured in one of the following:

• Function Points (FP)
• Source Lines of Code

DEFECT DENSITY FORMULA

USES

• For comparing the relative number of defects in various software components so that high-risk components can be identified and resources focused towards them.
• For comparing software/products so that quality of each software/product can be quantified and resources focused towards those with low quality.

Bug Life Cycle (BLC)

Introduction:

Bug can be defined as the abnormal behavior of the software. No software exists without a bug. The elimination of bugs from the software depends upon the efficiency of testing done on the software. A bug is a specific concern about the quality of the Application under Test (AUT).

Bug Life Cycle:

In software development process, the bug has a life cycle. The bug should go through the life cycle to be closed. A specific life cycle ensures that the process is standardized. The bug attains different states in the life cycle. The life cycle of the bug can be shown diagrammatically as follows:


The different states of a bug can be summarized as follows:
1. New
2. Open
3. Assign
4. Test
5. Verified
6. Deferred
7. Reopened
8. Duplicate
9. Rejected and
10. Closed

Description of Various Stages:

1. New: When the bug is posted for the first time, its state will be “NEW”. This means that the bug is not yet approved.
2. Open: After a tester has posted a bug, the lead of the tester approves that the bug is genuine and he changes the state as “OPEN”.
3. Assign: Once the lead changes the state as “OPEN”, he assigns the bug to corresponding developer or developer team. The state of the bug now is changed to “ASSIGN”.
4. Test: Once the developer fixes the bug, he has to assign the bug to the testing team for next round of testing. Before he releases the software with bug fixed, he changes the state of bug to “TEST”. It specifies that the bug has been fixed and is released to testing team.
5. Deferred: The bug, changed to deferred state means the bug is expected to be fixed in next releases. The reasons for changing the bug to this state have many factors. Some of them are priority of the bug may be low, lack of time for the release or the bug may not have major effect on the software.
6. Rejected: If the developer feels that the bug is not genuine, he rejects the bug. Then the state of the bug is changed to “REJECTED”.
7. Duplicate: If the bug is repeated twice or the two bugs mention the same concept of the bug, then one bug status is changed to “DUPLICATE”.
8. Verified: Once the bug is fixed and the status is changed to “TEST”, the tester tests the bug. If the bug is not present in the software, he approves that the bug is fixed and changes the status to “VERIFIED”.
9. Reopened: If the bug still exists even after the bug is fixed by the developer, the tester changes the status to “REOPENED”. The bug traverses the life cycle once again.
10. Closed: Once the bug is fixed, it is tested by the tester. If the tester feels that the bug no longer exists in the software, he changes the status of the bug to “CLOSED”. This state means that the bug is fixed, tested and approved.
While defect prevention is much more effective and efficient in reducing the number of defects, most organization conducts defect discovery and removal. Discovering and removing defects is an expensive and inefficient process. It is much more efficient for an organization to conduct activities that prevent defects.