我对于为什么这个测试不起作用感到困惑。只有在我给桩方法 `bar` 添加一个返回值时，它才起作用。然而，预期并不希望有一个返回值，所以我只想测试 `foo` 方法内部是否调用了 `bar`。
```ruby
class Event < ApplicationRecord
  def foo
    bar
  end
end

describe Event, type: :model do
  it '调用 bar' do
    event = create(:event)
    
    allow(event).to receive(:bar)
    expect(event.foo).to receive(:bar)
  end
end
错误信息:
Failure/Error: expect(event.foo).to receive(:bar)
     
  (nil).bar(*(any args))
     期望: 任意参数出现1次
     收到: 任意参数未出现

describe Event, type: :model do
  it '调用 bar' do
    event = create(:event)
    
    allow(event).to receive(:bar).and_return(true)
    expect(event.foo).to eq(true)
  end
end

<details>
<summary>英文:</summary>
I&#39;m confused as to why this test isn&#39;t working. It only works when I add a return value to the stubbed `bar` method. However, it is not expected to have a return value, so I only want to test `bar` is called within `foo`. 

This test does not work. 

allow(event).to receive(:bar)
expect(event.foo).to receive(:bar)

When I change the test to add a return value the test works. 

allow(event).to receive(:bar).and_return(true)
expect(event.foo).to eq(true)

</details>
# 答案1
**得分**: 1
```plaintext
在这张图片中有很多问题。
让我们从方法开始：

当你调用 `Event.new.foo` 时，你在 `self` 上调用 `#bar`，它是 Event 的实例，而不是方法 `foo`。
如果你做 `expect(event.foo).to receive(:bar)`，你是在方法的返回值上设置期望，这当然不起作用。
如果你想测试调用 foo 是否会调用 bar，你可以在之前设置期望使用 `expect(obj).to recieve :method_name`：
```lang-ruby
describe Event, type: :model do
  it 'calls bar' do
    event = create(:event)
    expect(event).to receive(:bar)
    event.foo
  end
end

describe Event, type: :model do
  it 'calls bar' do
    # 安排
    event = create(:event) 
    allow(event).to receive(:bar) 
    # 行动
    event.foo
    # 断言
    expect(foo).to have_recieved(:bar)
  end
end

<details>
<summary>英文:</summary>
There is a lot of things wrong in this picture. 
Lets start with the method:

When you call `Event.new.foo` you're calling `#bar` on `self` which is the instance of Event. Not on the method `foo`. 
If you do `expect(event.foo).to receive(:bar)` you're setting the expectation on the return value of the method which of course doesn't work.
If you want to test that calling foo calls bar you can use `expect(obj).to recieve :method_name` if you want to set the expectation before hand:
````lang-ruby
describe Event, type: :model do
  it 'calls bar' do
    event = create(:event)
    expect(event).to receive(:bar)
    event.foo
  end
end

describe Event, type: :model do
  it 'calls bar' do
    # arrange
    event = create(:event) 
    allow(event).to receive(:bar) 
    # act
    event.foo
    # assert
    expect(foo).to have_recieved(:bar)
  end
end

发表问题后找到答案：

允许(event).接收(:bar)
期望(event).接收(:bar)
event.foo