ruby - serverspec 命令返回空白字符串

Question

我正在尝试使用 rspec、serverspec 和 docker-api gems 测试 Dockerfile。在大多数情况下，我的测试都通过了，但所有使用 command 方法的测试都失败了，无论我提供的是什么命令，都会返回空白字符串。

代码可以在 GitHub 上找到但最重要的文件如下:

我的 Dockerfile:

# Dockerfile for nginx with configurable persistent volumes

# Select nginx as the base image
FROM nginx

# Mount configurable persistent volumes
VOLUME ["/etc/nginx/sites-enabled", "/etc/nginx/certs", "/etc/nginx/conf.d", "/var/log/nginx", "/var/www/html"]

# Expose both HTTP and HTTPS ports
EXPOSE 80 443

# ENTRYPOINT
ENTRYPOINT ["service", "nginx", "start"]

gem 文件:

source 'https://rubygems.org'

# See https://github.com/sstephenson/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby

group :development, :test do
  gem 'specinfra',  '~> 2.12.7'
  gem 'serverspec', '~> 2.8.2'
  gem 'docker-api', '~> 1.21.4'
  gem 'rspec',      '~> 3.2.0'
end

规范:

require 'serverspec'
require 'docker'

Excon.defaults[:ssl_verify_peer] = false

describe 'Dockerfile' do
  before(:all) do
    image =  Docker::Image.build_from_dir('.')

    set :os, family: :debian
    set :backend, :docker
    set :docker_image, image.id
  end

  it 'installs the right version of Debian' do
    expect(os_version).to include('Debian GNU/Linux 7')
  end

  describe package('nginx') do
    it { should be_installed }
  end

  describe service('nginx') do
    it { should be_enabled }
    it { should be_running }
  end

  describe command('nginx -V') do
    its(:stdout) { should include('http_ssl_module') }
    its(:stdout) { should include('http_gzip_static_module') }
  end

  describe port(80) do
    it { should be_listening }
  end

  describe port(443) do
    it { should be_listening }
  end

  def os_version
    command('lsb_release -a').stdout
  end
end

我知道我使用的是旧版本的 gems，但我无法在最新版本中使用它。如果它与我在 OS X 上有任何相关性，因此使用 boot2docker。我从运行规范中得到的结果是:

Failures:

  1) Dockerfile installs the right version of Debian
     Failure/Error: expect(os_version).to include('Debian GNU/Linux 7')
       expected "" to include "Debian GNU/Linux 7"

     # ./spec/dockerfile_spec.rb:16:in `block (2 levels) in <top (required)>'

  2) Dockerfile Command "nginx -V" stdout should include "http_ssl_module"
     Failure/Error: its(:stdout) { should include('http_ssl_module') }
       expected "" to include "http_ssl_module"

     # ./spec/dockerfile_spec.rb:29:in `block (3 levels) in <top (required)>'

  3) Dockerfile Command "nginx -V" stdout should include "http_gzip_static_module"
     Failure/Error: its(:stdout) { should include('http_gzip_static_module') }
       expected "" to include "http_gzip_static_module"

     # ./spec/dockerfile_spec.rb:30:in `block (3 levels) in <top (required)>'

Answer 1

当上游 specinfra gems(Specinfra 2.37.0 和 2.37.1)随着 stderr 和 stdout 的处理而改变时，我遇到了类似的事情。尝试使用重定向手动运行命令以查看输出的来源:

nginx -V 2>/dev/null

如果你最终没有输出，那么它就会输出到 stderr 中。解决方法是在末尾使用 2>&1 将所有内容放入标准输出。

** 根据评论更新

~$ nginx -V
nginx version: nginx/1.4.4
built by gcc 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5)
TLS SNI support enabled
<snip>
~$ nginx -V 2>/dev/null
~$