An example of code coverage with Gulp

gulpfile.js

var gulp = require('gulp');
var istanbul = require('gulp-istanbul');
var mocha = require('gulp-mocha');

gulp.task('test', function (cb) {
    gulp.src(['lib/**/*.js', 'web.js', 'api.js'])
        .pipe(istanbul()) // Covering files
        .on('finish', function () {
            gulp.src(['test/**/*.js'])
                .pipe(mocha())
                .pipe(istanbul.writeReports({
                    dir: './coverage',
                    reporters: [ 'lcov', 'json', 'text', 'text-summary' ],
                    reportOpts: { dir: './coverage' }
                })) // Creating the reports after tests runned
                .on('end', cb);
        });
});