提供者状态

关于这一高级话题，请先阅读提供者状态一节的介绍。

当按照以下形式来阅读时，提供者状态中的文本应该具有足够的可读性（自动生成的文档是按这样的形式展示的）：

Given an alligator with the name Mary exists *

Upon receiving a request to retrieve an alligator by name ** from Some Consumer

With {“method” : “get”, “path” : “/alligators/Mary” }

Some Provider will respond with { “status” : 200, …}

* 代表提供者状态

** 代表请求描述

消费者代码库

举个例子，消费者项目中用于创建一段契约的代码可能看起来像这样：

  1. describe MyServiceProviderClient do
  3.   subject { MyServiceProviderClient.new }
  5.   describe "get_something" do
  6.     context "when a thing exists" do
  7.       before do
  8.         my_service.given("a thing exists").
  9.           upon_receiving("a request for a thing").with(method: 'get', path: '/thing').
  10.           will_respond_with(status: 200,
  11.             headers: { 'Content-Type' => 'application/json' },
  12.             body: { name: 'A small something'} )
  13.       end
  15.       it "returns a thing" do
  16.         expect(subject.get_something).to eq(SomethingModel.new('A small something'))
  17.       end
  18.     end
  20.     context "when a thing does not exist" do
  21.       before do
  22.         my_service.given("a thing does not exist").
  23.           upon_receiving("a request for a thing").with(method: 'get', path: '/thing').
  24.           will_respond_with(status: 404)
  25.       end
  27.       it "returns nil" do
  28.         expect(subject.get_something).to be_nil
  29.       end
  30.     end
  31.   end
  32. end

提供者代码库

根据上述的提供者状态，来定义能够创建适当数据的服务提供者状态，可以在服务提供者项目中这样来写。（此处的消费者名称必须与消费者项目中配置的消费者名称相符，才能正确地找到这些提供者状态。）

  1. # In /spec/service_consumers/provider_states_for_my_service_consumer.rb
  3. Pact.provider_states_for 'My Service Consumer' do
  5.   provider_state "a thing exists" do
  6.     set_up do
  7.       # Create a thing here using your framework of choice
  8.       # eg. Sequel.sqlite[:somethings].insert(name: "A small something")
  9.     end
  11.     tear_down do
  12.       # Any tear down steps to clean up your code
  13.     end
  14.   end
  16.   provider_state "a thing does not exist" do
  17.     no_op # If there's nothing to do because the state name is more for documentation purposes,
  18.           # you can use no_op to imply this.
  19.   end
  21. end

在pact_helper.rb中引入上面所写的提供者状态文件

  1. # In /spec/service_consumers/pact_helper.rb
  3. require './spec/service_consumers/provider_states_for_my_service_consumer.rb'

基状态

对于给定消费者来定义一些能够在每次交互前/后都会运行的代码，而不管是否指定了提供者状态，只需将set_up/tear_down代码块放置于provider_state之外即可。

  1. Pact.provider_states_for 'My Service Consumer' do
  3.   set_up do
  4.     # This will run before the set_up for provider state specified for the interaction.
  5.     # eg. create API user, set the expected basic auth details
  6.   end
  8.   tear_down do
  9.     # ...
  10.     # This will run after the tear_down for the specified provider state.
  11.   end
  12. end

全局状态

全局状态会先于消费者定义的基状态之前被设置。避免使用全局设置来创建数据，因为当存在多个消费者时这会使测试变得脆弱。

  1. Pact.set_up do
  2.   # eg. start database cleaner transaction
  3. end
  5. Pact.tear_down do
  6.   # eg. clean database
  7. end

测试错误响应

测试客户端如何处理错误的响应是非常重要的。

  1. # Consumer codebase
  3. describe MyServiceProviderClient do
  5.   subject { MyServiceProviderClient.new }
  7.   describe "get_something" do
  9.     context "when an error occurs retrieving a thing" do
  10.       before do
  11.         my_service.given("an error occurs while retrieving a thing").
  12.           upon_receiving("a request for a thing").with(method: 'get', path: '/thing').
  13.           will_respond_with(
  14.             status: 500,
  15.             headers: { 'Content-Type' => 'application/json' },
  16.             body: { message: "An error occurred!" } )
  17.       end
  19.       it "raises an error" do
  20.         expect{ subject.get_something }.to raise_error /An error occurred!/
  21.       end
  23.     end
  24.   end
  25. end
  1. # Provider codebase
  3. Pact.provider_states_for 'My Service Consumer' do
  4.   provider_state "an error occurs while retrieving a thing" do
  5.     set_up do
  6.       # Stubbing is ususally the easiest way to generate an error with predictable error text.
  7.       allow(ThingRepository).to receive(:find).and_raise("An error occurred!")
  8.     end
  9.   end
  10. end

在set_up和tear_down中使用引入的模块

按照这种方法引入的任意模块在set_up与tear_down代码块中都是可以使用的。 这样做的一个常见用途是将用于设置数据的工厂方法包含进来，这样提供者状态文件将不会过于臃肿。

  1. Pact.configure do | config |
  2.   config.include MyTestHelperMethods
  3. end