Hacker News Reader

Parent Full thread

turtleyacht

Mutation testing with Java pitest measures three things: line coverage, mutation coverage, and test strength.

Jacoco measures both line and branch coverage, same as Jest.

Preferred thing to do is establish a baseline, and then

* Write tests for new features going forward.

* Write tests for fixes to production incidents.

Don't let things get worse than baseline. (The number will vary from repo to repo.)

View on HN

So how do you decide what should be the baseline on a brand new project? 70%? 80% 90% ? :-)

Good question. Depends on the reference template, if there is one. Otherwise, Unit Testing: Principles, Practices, and Patterns (Khorikov 2020) suggests

---

Let me repeat myself: coverage metrics are a good negative indicator, but a bad positive one. Low coverage numbers--say, below 60%--are a certain sign of trouble. They mean there's a lot of untested code in your code base. But high numbers don't mean anything. Thus, measuring the code coverage should be only a first step on the way to a quality test suite.

Reply on news.ycombinator.com