Defect age and Defect spoilage

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Permalink Reply by Stefan Steinbauer on January 8, 2010 at 2:55pm

The defect age is often calculated as a phase age (ie: how many phases it exists). Because defects are more expensive the later in the test they are found, it is a good idea to also calculate the defect spoilage which is a quotient.

sum of (number x phaseAge)
defect spoilage = ---------------------------------------
total number of defects

You can find a lot more numbers in "Systematic software testing "
Both numbers can be very hard to calculate or even finding all the facts. Try once and you will see :-)

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Permalink Reply by Abhijeet Bhagat on January 9, 2010 at 9:13pm

Defect Age : The time or phase since the defect is open.
Defect Age Calculated in Time : The Number of hours /days the defect is open. if the defect is fixed then Defect Age=Date Fixed less Defect found date.

Defect Age Calculated in Phases : Defect Fixed Phase - Defect Injection phase.
Let’s say the software life cycle has the following phases:

1. Requirements Development
2. High-Level Design
3. Detail Design
4. Coding
5. Unit Testing
6. Integration Testing
7. System Testing
8. Acceptance Testing
If a defect is identified in ‘System Testing’ and the defect was introduced in ‘Requirements Development’, the Defect Age is 6.

Defect age is used in another metric called defect spoilage to measure the effectiveness of defect removal activities.

Spoilage = Sum of (Number of Defects x defect age) / Total number of defects.
low values of defect spoilage mean more effective defect discovery process.

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