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Friday, December 24, 2010

What is a Metric? What are different metrics used for testing?

Metric is a measure to quantify software, software development resources and/or software development process. A metric can quantify any of the following factors:
- Schedule
- Work Effort
- Product Size
- Project Status
- Quality Performance
Metric enables estimation of future work. That is, considering the case of testing depending the product is fit for shipment or delivery depends on the rate the defects are found and fixed. Defect collected and fixed is one kind of metric. It is beneficial to classify metrics according to their usage.
Defects are analyzed to identify which are the major causes of defect and which is the phase that introduces most defects. This can be achieved by performing pareto analysis of defect causes and defect introduction phases. The main requirements for any of these analysis is Software Defect Metrics.
Metric is represented as percentage. It is calculated at stage completion or project completion. It is calculated from bug reports and peer review reports.

Few of the Defect Metrics are:

- Defect Density: (Number of defects reported by SQA + Number of defects reported by peer review)/ Actual Size.
The size can be in KLOC, SLOC, or Function points. The method used in the organization to measure the size of the software product. The SQA is considered to be the part of the software testing team.

- Test Effectiveness: t/(t+Uat) where t= total number of defects reported during testing and Uat= total number of defects reported during user acceptance testing. User acceptance testing is generally carried out using the acceptance test criteria according to the acceptance test plan.

- Defect removal Efficiency:
(Total number of Defects Removed / Total Number of Defects Injected) * 100 at various stages of SDLC. This metric will indicate the effectiveness of the defect identification and removal in stages for a given project.

Requirements: DRE = [(Requirements defects corrected during requirements phase)/(Requirement Defects injected during requirements phase)] * 100
Design: DRE = [(Design defects corrected during design phase)/(Defects identified during requirements phase + Defects injected during design phase)] * 100
Code: DRE = [(Code defects corrected during coding phase)/(Defects identified during requirements phase + Defects identified during design phase + Defects injected during design phase)] * 100
Overall: DRE = [(Total defects corrected at all phases before delivery) / (Total defects detected at all phases before and after delivery)] * 100

- Defect Distribution: Percentage of Total defects distributed across requirements analysis, design reviews, code reviews, unit tests, integration tests, system tests, user acceptance tests, review by project leads and project managers.

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