Cucumber test double：场景失败但其步骤通过

Question

我正在使用The RSpec Book 学习 Rspec + Cucumber。我才刚刚开始，正在开发 Codebreaker 游戏。

其中有一个功能“Codebreaker 开始游戏”，它代表用户在 shell 中键入命令并得到两个响应：“欢迎使用 Codebreaker！”和“输入猜测：”。这是该功能的外观：

Feature: code-breaker starts game
   As a code-breaker
   I want to start a game
   So that I can break the code

   Scenario: start game
      Given I am not yet playing
      When I start a new game
      Then I should see "Welcome to Codebreaker!"
      And I should see "Enter a guess:"

由于cucumber 脚本使用了输出，因此本书正在创建一个模拟对象output，它期望接收带有Welcome to Codebreaker! 和Enter a guess: 参数的puts 消息。这是它在步骤定义中的样子：

#the mock object
class Output
   def messages
      @messages ||= []
   end

   def puts(message)
      messages << message
   end
end

def output
   @output ||= Output.new
end

Given /^I am not yet playing$/ do
end

When /^I start a new game$/ do
   game = Codebreaker::Game.new(output)
   game.start
end

Then /^I should see "([^"]*)"$/ do |message|
   output.messages.should include(message)
end

好的，到现在都没问题。

做这个练习，我记得之前看过rspeck doubles框架可以用在cucumber里面，所以我想我可以稍微清理一下。

首先，我在support/env.rb 中包含了rspeck doubles 框架：

require 'cucumber/rspec/doubles'

然后我更改了步骤定义：

Given /^I am not yet playing$/ do
end

When /^I start a new game$/ do
   @output = double('output').as_null_object #the mock object
   game = Codebreaker::Game.new(@output)
   game.start
end

Then /^I should see "([^"]*)"$/ do |message|
   @output.should_receive(:puts).with(message)
end

奇怪的想法是，现在，当我用黄瓜执行功能时，在总结中我得到了所有 4 个步骤，但不是整个场景。这怎么可能？这是怎么回事？这是我从命令行得到的输出：

Feature: code-breaker starts game
   As a code-breaker
   I want to start a game
   So that I can break the code

  Scenario: start game                          # features/codebreaker_starts_game.feature:6
    Given I am not yet playing                  # features/step_definitions/codebreaker_steps.rb:1
    When I start a new game                     # features/step_definitions/codebreaker_steps.rb:4
    Then I should see "Welcome to Codebreaker!" # features/step_definitions/codebreaker_steps.rb:10
    And I should see "Enter a guess:"           # features/step_definitions/codebreaker_steps.rb:10
      (Double "output").puts("Welcome to Codebreaker!")
          expected: 1 time
          received: 0 times (RSpec::Mocks::MockExpectationError)
      /home/a_user/www/codebreaker/features/step_definitions/codebreaker_steps.rb:11:in `block in <top (required)>'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/error_generator.rb:80:in `__raise'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/error_generator.rb:39:in `raise_expectation_error'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/message_expectation.rb:251:in `generate_error'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/message_expectation.rb:207:in `verify_messages_received'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/method_double.rb:117:in `block in verify'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/method_double.rb:117:in `each'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/method_double.rb:117:in `verify'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/proxy.rb:88:in `block in verify'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/proxy.rb:88:in `each'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/proxy.rb:88:in `verify'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/methods.rb:116:in `rspec_verify'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/space.rb:11:in `block in verify_all'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/space.rb:10:in `each'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks/space.rb:10:in `verify_all'
      /var/lib/gems/1.9.1/gems/rspec-mocks-2.10.1/lib/rspec/mocks.rb:19:in `verify'
      /var/lib/gems/1.9.1/gems/cucumber-1.1.9/lib/cucumber/rspec/doubles.rb:12:in `After'

Failing Scenarios:
cucumber features/codebreaker_starts_game.feature:6 # Scenario: start game

1 scenario (1 failed)
4 steps (4 passed)
0m0.009s

Answer 1

当您设置像should_receive 这样的期望时，您指定在将来的某个时间点应该调用指定的方法 - 之前发生的任何事情都将被忽略（否则应该是 have_received 或类似的东西过去时）。

在您的代码中，您在 Then 步骤中设置了期望，但该方法在您的 When 步骤（即之前）中被调用，因此此时没有设置期望。您的双重设置允许调用任何方法，因此您不会收到任何错误，但是当规范检查最后是否满足所有期望时，它会拒绝并引发异常