Thursday, 8 May 2014

The Cost of Finding Defects

Problem: Calculating the cost of finding a defect

One of my peers asked me how I would calculate the cost of finding a bug the other day. Reason for the quastion was that management was doing a RoI calculation on the test effort in the project portfolio, and would like to know how much effort (read: money) they would be spending to find a single bug.

Solution: Guesstimating based on a few metrics

In nature knowing the price-tag for finding a defect is interesting, and my answer to the question was something like this:

Gather some metrics from your test management tool, test plans, timelogging system or similar.

Something like total number of test cases (TC) and defects fount, hours spend on TC preparation and TC execution

Apply simple math like:

((hours spend on TC preparation + hours spend on TC execution)/ total test cases)* Defect to test case ratio (Defects / TC)

For example:

((442 + 159)/102)*(98/102) = 5,66 man hours / defect.

That excludes all the cost like test environment cost, training of testers, time spend on defect management etc.

Happy guesstimating!