gulpfile.coffee

# npm install gulp gulp-util gulp-mocha mocha coffee-script assert
gulp = require 'gulp'
gutil = require 'gulp-util'
mocha = require 'gulp-mocha'

gulp.task 'test', ->
  gulp.src('test.coffee').pipe(mocha()).on('error', gutil.log)

gulp.task 'default', ->
  gulp.watch('test.coffee', 'test').on('error', gutil.log)
    

gulpfile.js

require('coffee-script/register');
require('./gulpfile.coffee');

test.coffee

assert = require 'assert'

describe 'A test', ->
  it 'should not abort gulp.watch() when it fails', ->
    value = 'foo'
    expected = 'foo' # Change this after running gulp.
    assert.equal expected, value