An introduction and future of Ruby coverage library

Are you using code coverage? As Ruby is a dynamic language and there is no standard static code checker yet, a good test suite is crucial to write a production-level Ruby code. Code coverage is a measure of test goodness. Therefore, it is also important to (properly) use code coverage to take a hint about whether your test suite is good enough or not yet (and if any, which modules are not tested well). We talk an introduction to code coverage, types and usage of code coverage, the current status of Ruby coverage library, and some planned improvements towards Ruby 2.5.