Test Effort Estimation

Test Effort Estimation

Test engineering managers use many different methods to estimate and schedule their test engineering efforts. Different organizations use different methods depending on the type of projects, the inherent risks in the project, the technologies involved etc. Most of the time, test effort estimations are clubbed with the development estimates and no separate figures are available.

Ad-hoc method

The test efforts are not based on any definitive timeframe. The efforts continue until some pre-decided timeline set by managerial or marketing personnel is reached. Alternatively, it is done until the budgeted finances run out. This is a practice prevalent in extremely immature organizations and has error margins of over 100% at times.

·         Percentage of development time

The fundamental premise here is that test engineering efforts are dependent on the development time / effort. First, development effort is estimated using some techniques such as LOC or Function Points. The next step is using some heuristic to peg a value next to it. This varies widely and is usually based on previous experiences. This method is not defendable since it is not based on any scientific principles or techniques. Schedule overruns could range from 50 – 75% of estimated time. This method is also by far the most used.

·         From the Function Point estimates

Capers Jones estimates that the number of test cases can be determined by the function point estimate for the corresponding effort. The formula is

Number of Test Cases = (Function Points)^1.2

The actual effort in person-hours is then calculated with a conversion factor obtained from previous project data. The disadvantage of using FP is that they require detailed requirements in advance. Another issue is that modern object-oriented systems are designed with Use Cases in mind and this technique is incompatible with them.