double和spy有什么区别？

Question

我阅读spies，我不能看到这之间的差异德：这个

RSpec.describe "have_received" do 
    it "passes when the message has been received" do 
    invitation = spy('invitation', deliver: "ok") 
    invitation.deliver 
    expect(invitation).to have_received(:deliver) 
    end 
end 

和：

RSpec.describe "have_received" do 
    it "passes when the message has been received" do 
    invitation = double('invitation', deliver: "ok") 
    invitation.deliver 
    expect(invitation).to have_received(:deliver) 
    end 
end 

两个例子都通过没有问题。我看不出任何优势使用spy

Answer 1

正如@max在评论中所说，区别在于我可以使用spy而不用说deliver: "ok"。所以，运行这个：

RSpec.describe "have_received" do 
    it "passes when the message has been received" do 
    invitation = spy('invitation') 
    invitation.deliver 
    expect(invitation).to have_received(:deliver) 
    end 
end 

RSpec.describe "have_received" do 
    it "passes when the message has been received" do 
    invitation = double('invitation') 
    invitation.deliver 
    expect(invitation).to have_received(:deliver) 
    end 
end 

第一个例子会通过，但不是第二个。

现在我明白这是什么意思？

“你可以使用任何测试双（或部分双）作为间谍，但双必须设置刺探消息你关心的是间谍自动监视所有消息，或者你可以允许一条消息窥探它。“