Estimation of testing effort is not an easy task. From my experience, I found several ways to do estimation of testing effort. Examples are:
- 30% of development effort.
- Equal to development effort (e. g. two weeks development = two weeks testing – Agile approach).
- Based on objectives.
The third approach is the one preferred by Robert Sabourin. He describes it by defining the specific test objectives of the project then specifying the size and complexity of each objective. Using data from past projects for same test objectives of size and complexity, identify min, max and typical values. Calculate (min + max + 4x typical) / 6 gives an estimate. Then testers should work with stakeholders to prioritize and then scope the objectives.