gulpfile.js

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

gulp.task('lint', function() {
    // ESLint ignores files with "node_modules" paths.
    // So, it's best to have gulp ignore the directory as well.
    // Also, Be sure to return the stream from the task;
    // Otherwise, the task may end before the stream has finished.
    return gulp.src(['**/*.js', '!node_modules/**', '!coverage/**'])
        // eslint() attaches the lint output to the "eslint" property
        // of the file object so it can be used by other modules.
        .pipe(eslint())
        // eslint.format() outputs the lint results to the console.
        // Alternatively use eslint.formatEach() (see Docs).
        .pipe(eslint.format())
        // To have the process exit with an error code (1) on
        // lint error, return the stream and pipe to failAfterError last.
        .pipe(eslint.failAfterError());
});

gulp.task('pre-test', function() {
    return gulp.src(['lib/**/*.js'])
        // Covering files
        .pipe(istanbul({
            includeUntested: true
        }))
        // Force `require` to return covered files
        .pipe(istanbul.hookRequire());
});

gulp.task('test', function() {
    return gulp.src(['test/**/*.js'])
        .pipe(mocha({
            reporter: 'spec'
        }))
        // Creating the reports after tests ran
        .pipe(istanbul.writeReports())
        // Enforce a coverage of at least 90%
        .pipe(istanbul.enforceThresholds({
            thresholds: {
                global: 95
            }
        }));
});

gulp.task('default', ['lint', 'pre-test', 'test']);