5.5Risk Coverage: Are You Testing the Right Things?

Beyond Code Coverage

Code coverage measures how much code is tested. Risk coverage measures whether the most important parts are tested.

Risk-Weighted Coverage

Risk-Weighted Coverage = Sum(Coverage_i x Risk_i) / Sum(Risk_i)

Where:
  Coverage_i = test coverage of area i (0-100%)
  Risk_i = risk score of area i (1-5)

Example:

Area	Code Coverage	Risk Score	Weighted Contribution
Payment	95%	5	95 x 5 = 475
Authentication	88%	5	88 x 5 = 440
Search	72%	3	72 x 3 = 216
Admin tools	45%	2	45 x 2 = 90
Marketing pages	20%	1	20 x 1 = 20

Risk-Weighted Coverage = (475 + 440 + 216 + 90 + 20) / (5 + 5 + 3 + 2 + 1)
                       = 1241 / 16
                       = 77.6%

This is more meaningful than the unweighted average (64%) because it gives more credit for covering high-risk areas.