ruby - double 和 spy 和有什么不一样？

Question

我正在阅读 spies我看不出这之间有什么区别:

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

还有这个:

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

两个例子都顺利通过。我看不到使用 spy

有任何优势

Answer 1

正如@max 在评论中所说，不同之处在于我可以使用 spy 而无需说 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

第一个示例会通过，但第二个不会。

现在我明白这意味着什么了......

“您可以使用任何测试替身(或部分替身)作为 spy ，但必须将替身设置为监视您关心的消息。 spy ​​会自动监视所有消息，或者您可以允许消息监视它。”