Make sure all your code is tested, don't miss anything. CoverJS intruments your code. Using the instrumented code with your tests will result in a nice object, which can be passed through one of the reporters to create a nice graphical output of your code.
Instead of instrumenting lines (like JSCoverage), CoverJS will instrument statements, which should result in a more precise result.
To instrument the code, CoverJS comes with a CLI tool:
coverjs --output cov/ file.js test/*
The instrumented code should be executed to count the number of calls for each statement.
Usually your tests will try to cover each statement.
An example code that will capture the output and generate a HTML report would look like:
var HTMLReporter = ;;var reporter = global__$coverObject;console;
The output stream can be redirected to a file using
node test.js > report.html
so the result can be viewed in a browser
There are different templates with which what the instrumented code should start and end. For node there exists an template that saves the output as a JSON file, which can later be used as to generate a HTML report.
coverjs --template node --report ./cov.json file.js
coverjs-report tool, which reads from
stdin, an HTML output can be
cat ./cov.json | coverjs-report -r html > cov.html
See the prime Makefile for an example.