How Much Test Coverage Is Enough?
Continue Reading March 24th, 2009 Handerson Gomes
There is a lot of talk these days about 100% test coverage and if we should strive to reach it. I honestly think that 100% test coverage is a hot topic because it can be easily measured.
To me the most important question is how much test coverage is enough.
I would like to discuss test coverage by making an analogy with exercise.
We all know that exercising, like testing, is a good thing. We also know that there is a range that dictates the minimum and maximum amount of exercise that will be beneficial. Too little exercise and nothing happens, too much and it can hurt and even cause permanent damage.
How much exercise is enough? Will I be healthy if I start running some miles every week? Probably yes. Would I be even healthier if I (try) to run 1000 miles every week? Most likely not.
It is the same thing with testing. Can I definitely say that a product with 60% test coverage is “healthier” than a product with 1%? Not definitely, but plausibly yes, to the point that I can bet on it, and I’m not a gambler. How about a product with 40% and one with 50% test coverage? From a “healthy” perspective it is hard to assume that one is better than the other by looking only at the coverage. (A theme for another post would be to discuss if High Test Coverage is a cause or consequence of the fitness of a product).
