如何在我的rails minitest中使用模拟？

Question

有两个类，UserDevice（<ActiveRecord :: Base）和NotificationAdapter。
在NotificationAdapter中，我使用AWS SDK，而UserDevice使用NotificationAdapter实例。
联合点在下面，

protected def notificationAdapter
  @notificationAdapter ||= NotificationAdapter.new(self)
end

在UserDevice测试中，我想制作临时NotificationAdapter模拟以替换原始的NotificationAdapter，并仅在测试中使用此模拟。
但是我不知道该怎么办，因为这是我在测试中使用模拟的第一种情况。

我认为这需要执行以下两个步骤，

1. 在测试代​​码中创建临时NotificationAdapter类（NorificationAdapterMock）。

   NotificationAdapterMock = MiniTest::Mock.new mock.expect :setEndpoint, 'arn:testEndpoint' mock.expect :subscribeToAnnouncement, true

2. 将UserDevice的notificationAdapter方法更改为以下内容，

   protected def notificationAdapter @notificationAdapter ||= NotificationAdapterMock end

但我不知道这是对还是错。我该怎么办？

Answer 1

你需要

1. mock您的NotificationAdapter，因此它不会触发网络，但会做一些安全，容易的事情
2. 还要确保适配器正确接线

旁注：请遵循ruby样式准则，方法名称和变量应使用蛇形而不是驼峰式。

因此，我们可以这样写：

require 'minitest/autorun'

class NotificationAdapter
  def initialize(device)
    @device = device
  end

  def notify
    # some scary implementation, that we don't want to use in test
    raise 'Boo boo!'
  end
end

class UserDevice
  def notification_adapter
    @notification_adapter ||= NotificationAdapter.new(self)
  end

  def notify
    notification_adapter.notify
  end
end

describe UserDevice do
  it 'should use NotificationAdapter for notifications' do
    device = UserDevice.new

    # create mock adapter, that says 'ohai!' on notify
    mock_adapter = MiniTest::Mock.new
    mock_adapter.expect :notify, 'ohai!'

    # connect our mock, so next NoficationAdapter.new call will return our mock
    # and not usual implementation
    NotificationAdapter.stub :new, mock_adapter do
      device.notify.must_equal 'ohai!'
    end
  end
end

有关更多信息，请参见MiniTest的有关模拟和存根的文档。

但是，我们不要在这里停下来！我建议您将业务逻辑从ActiveRecord模型移至单独的服务类。这将具有以下良好效果：

1. 您的模型变薄
2. 功能被很好地封装在其自己的类中，并且现在遵循“单一责任原则”
3. 您的测试变得非常快，因为您不需要加载Rails并可以模拟您的模型。

这里是：

require 'minitest/autorun'

# same adapter as above
class NotificationAdapter
  def initialize(device)
    @device = device
  end

  def notify
    raise 'Boo boo!'
  end
end

class UserDevice
# the logic has been moved out
end

class NotifiesUser

  def self.notify(device)
    adapter = NotificationAdapter.new(device)
    adapter.notify
  end
end

describe NotifiesUser do
  it 'should use NotificationAdapter for notifications' do
    # Let's mock our device since we don't need it in our test
    device = MiniTest::Mock.new

    # create mock adapter, that says 'ohai!' on notify
    mock_adapter = MiniTest::Mock.new
    mock_adapter.expect :notify, 'ohai!'

    # connect our mock, so next NoficationAdapter.new call will return our mock
    # and not usual implementation
    NotificationAdapter.stub :new, mock_adapter do
      NotifiesUser.notify(device).must_equal 'ohai!'
    end
  end
end

祝你今天愉快！

PS：如果您想了解有关隔离测试，模拟技术和常规“快速测试”运动的更多信息，我强烈建议您加里·伯恩哈特（Gary Bernhardt）的destroyallsoftware.com屏幕录像。这是有偿的东西，但是非常值得。