SOLVED: using yargs npm package
gulp = require 'gulp'
coffeelint = require 'gulp-coffeelint'
mocha = require 'gulp-mocha'
plumber = require 'gulp-plumber'
gutil = require 'gulp-util'
watch = require 'gulp-watch'
yargs = require 'yargs'
handleError = (err) ->
console.error err.message
process.exit 1
gulp.task 'test', ->
gulp.src('test/*-test.*')
.pipe(mocha(reporter: 'spec', grep: yargs.argv.grep))
.on 'error', handleError