RSpec: is_expect与expect的区别

Question

我这里有两个规格：

it 'is not an included preferred gender' do
  house.preferred_gender = 3
  is_expected.not_to be_valid
end

it 'is an included preferred gender' do
  house.preferred_gender = 2
  expect(house).to be_valid
end

我不明白的是，如果我在第二个规范expect(house).to be_valid中替换为is_expected.to be_valid，那么我的测试就失败了：

失败：

1) House preferred gender is an included preferred gender
     Failure/Error: is_expected.to be_valid
       expected #<House id: nil, rent: nil, deposit: nil, description: nil, preferred_gender: nil, created_at: nil, updated_at: nil, available_at: nil, user_id: nil, lease_length: nil, built_in: nil> to be valid, but got errors: User must exist, Rent can't be blank, Rent is not a number, Preferred gender can't be blank, Preferred gender is not included in the list, Available at can't be blank
     # ./spec/models/house_spec.rb:94:in `block (3 levels) in <main>'

Finished in 16.27 seconds (files took 3.02 seconds to load)
52 examples, 1 failure

这一切为什么要发生？提前谢谢！

Answer 1

is_expected被简单地定义为expect(subject)，是为您使用rspec期望值及其更新的基于预期的语法而设计的。

https://relishapp.com/rspec/rspec-core/docs/subject/one-liner-syntax

由于被测试的对象是house而不是subject，我假设subject没有初始化，因此被设置为defaul (described_class.new)。is_expected调用这个默认主题的期望。

要使用is_expected，初始化subject：

describe House do
   subject { House.new(...) } # or build :house if you use FactoryBot
   # ...
end