Rspec Stub获取模型

Question

如何在控制器中获取模型的存根？

示例：

# Model Spec
it 'does something' do
  allow(model).to receive(:value).and_return 100
  model2 = FactoryGirl.create :model
  allow(model2).to receive(:value).and_return 99
  # next line fails because it returns 100. when fetched, model2.value = 0
  expect(model.subtract_last_model).to eq 1
end

# Model
def subtract_last_model
 value - Model.last.value
end

我需要能够存根model2，又名Model.last来返回99。

当然，我可以编写以下代码，然后编写一个规范，看看是否用正确的参数调用了它，但我很好奇是否还有其他方法：

def subtract_model(model)
  value - model.value
end

Answer 1

很简单，只是存根Model和model2

it 'does something' do
  allow(model).to receive(:value).and_return 100
  model2 = FactoryGirl.create :model

  #  stub Model
  allow(Model).to receive(:last).and_return model2
  allow(model2).to receive(:value).and_return 99

  # next line fails because it returns 100. when fetched, model2.value = 0
  expect(model.subtract_last_model).to eq 1
end

Answer 2

Model.last不返回带存根的model2，而是从数据库重新加载model2的非存根版本。因此：

it 'does something' do
  allow(model).to receive(:value).and_return 100
  model2 = FactoryGirl.create :model
  allow(model2).to receive(:value).and_return 99

  allow(Model).to receive(:last).and_return(model2)

  expect(model.subtract_last_model).to eq 1
end