Code Coverage

Code coverage tells you how much of your code is covered by your tests. Higher code coverage can mean your code has a good chance of being well-tested and contain few bugs.

Let’s use a tool called Instanbul to check our code coverage.

Istanbul

Install Istanbul globally like this:

$ npm install -g istanbul

To run Istanbul’s coverage calculation with your Mocha tests, run:

istanbul cover _mocha

Instanbul generates a web page of the detailed results of its calculations to coverage/lcov-report/index.html. Look at this page to see which particular bits of your code aren’t being covered by your tests.