box: node:4.2.6-slim
dev:
  steps:
    - npm-install
    - internal/watch:
        code: grunt serve
        reload: true

build:

  steps:
    - script:
        code: export NODE_ENV='testing'
    - npm-install
    - script:
        name: echo nodejs information
        code: |
          echo "node version $(node -v) running"
          echo "npm version $(npm -v) running"
    - grunt:
        tasks: test
 
box: node:4.2.6-slim
dev:
  steps:
    - npm-install
    - internal/watch:
        code: grunt serve
        reload: true

build:

  steps:
    - script:
        code: export NODE_ENV='testing'
    - npm-install
    - script:
        name: echo nodejs information
        code: |
          echo "node version $(node -v) running"
          echo "npm version $(npm -v) running"
    - gulp:
        tasks: build
 
Change Wercker build step to Gulp
Change Wercker build step to Gulp