ruby-on-rails - 在调用将消息发送到所有实例的类方法时，测试类的实例是否接收到消息

Question

虽然正确，但标题需要一些解释:)

我有这堂课：

class Character
  include DataMapper::Resource

  def self.tick_all
    all.collect &:tick
  end

  def tick
    # do stuff
  end

end

如您所见，何时Character.tick_all调用其所有实例都应接收tick调用。它按预期工作：当我启动控制台时，里面的东西tick就完成了。但我无法通过测试：

describe ".tick_all" do
  let(:instance) { FactoryGirl.create(:character) }
  it "invokes #tick for every instance" do
    Character.tick_all
    instance.should_receive(:tick)
  end
end

失败的例子：

Failure/Error: instance.should_receive(:tick)
  (#<Character:0x00000002fa4e28>).tick(any args)
      expected: 1 time
      received: 0 times

Answer 1

期望应该在方法调用之前设置：

describe ".tick_all" do
  let(:instance) { FactoryGirl.create(:character) }
  it "invokes #tick for every instance" do
    instance.should_receive(:tick)
    Character.tick_all
  end
end

UPD：上面的代码不起作用。这个变种呢？

describe ".tick_all" do
  it "invokes #tick for every instance" do
    Character.any_instance.should_receive(:tick)
    Character.tick_all
  end
end

UPD2：Aaand 另一个版本：

describe ".tick_all" do
  it "invokes #tick for every instance" do
    tick_count = 0
    Character.any_instance.stub(:tick) { tick_count += 1 }
    Character.tick_all

    tick_count.should == Character.count
    # or
    # expect{ Character.tick_all }.to change{tick_count}.by(Character.count)
  end
end