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Ruby rspec期望值:有什么方法可以确保关键字期望值不是“虚假的”吗?

rspec-expectations rspec ruby

aarestad · 技术社区 · 11 月前

假设我有:

class Foo
  def do_thing(arg_one:, arg_two:)
    # ...
  end
end

class Bar
  def initialize(foo)
    @foo = foo
  end

  def do_delegated_thing
    @foo.do_thing(arg_one: "x", arg_two: "y")
  end
end

以及测试:

describe Bar do
  let(:mock_foo) do
    foo = double(Foo)
    allow(foo).to receive(:do_thing)
    foo
  end

  let(:subject) { described_class.new(mock_foo) }

  it "calls Foo with expected arguments" do
    subject.do_delegated_thing

    expect(mock_foo).to have_received(:do_thing).with(arg_one: "x", arg_two: "y")
  end
end

现在,假设我想重构 Foo 并更改参数名称:

class Foo
  def do_thing(arg_one_hundred:, arg_two:)
    # ...
  end
end

尽管预期 receive(:do_thing).with(arg_one: "x", arg_two: "y") 现在无效。在我心中, do_thing 不应期望使用无效参数调用。是否有一种合理的方法来解决这一问题,即我应该使用更好的RSpec API方法来确保期望的合法性?

1 回复 | 直到 11 月前

engineersmnky 11 月前

您当前发布的代码存在一些语法问题(见下文);然而,你正在寻找的是 Verifying Double 在这种情况下,a instance_double .

来自文件(着重部分为后加):

一 instance_double 是最常见的双重验证类型。它将类名或对象作为第一个参数,然后验证任何被存根的方法是否存在于例子那个班。此外当它接收消息时, 它验证所提供的参数是否得到方法签名的支持,包括arity和允许或必需的关键字参数(如果有的话) .

例如,如果您更改 foo = double(Foo) 到 foo = instance_double(Foo) 您的原始测试将通过,当您将方法更改为 def do_thing(arg_one_hundred:, arg_two:) 它将会失败。

代码当前存在的问题:

Bar#initialize 不接受任何这样的论点 described_class.new(mock_foo) 将引发错误。我不确定是否应该将争论视为依赖注入,因此在这里提出正确的解决方案更加困难。
to_receive 不是一种方法 allow(foo).to_receive(:do_thing) 将引发错误
expect(...).to recieve 但是,由于您已经调用了,因此设置了对象的期望值 subject.do_delegated_thing 在设置期望之前,期望总是会失败(在方法调用之前移动期望)

Working Example :(有明显修改)

class Foo
  def do_thing(arg_one:, arg_two:); end
end

class Baz
  def do_thing(arg_one_hundred:, arg_two:); end
end 

class Bar
  def initialize
    @foo = Foo.new
  end

  def do_delegated_thing
    foo.do_thing(arg_one: "x", arg_two: "y")
  end
  private 
     attr_reader :foo
end

describe Bar do
  let(:mock_foo) {instance_double(Foo, do_thing: nil)} 
  let(:mock_baz) {double(Baz, do_thing: nil)}
  let(:mock_baz_2) {instance_double(Baz, do_thing: nil)}

  let(:subject) { described_class.new }

  it "calls Foo with expected arguments" do
    allow(subject).to receive(:foo).and_return(mock_foo)
    expect(mock_foo).to receive(:do_thing).with(arg_one: "x", arg_two: "y")
    subject.do_delegated_thing
  end
  context 'comparing double and instance_double' do 
    it "calls double with unexpected arguments" do
      allow(subject).to receive(:foo).and_return(mock_baz)
      expect(mock_baz).to receive(:do_thing).with(arg_one: "x", arg_two: "y")
      subject.do_delegated_thing
    end
    it "calls instance_double with unexpected arguments" do
      allow(subject).to receive(:foo).and_return(mock_baz_2)
      expect(mock_baz_2).to receive(:do_thing).with(arg_one: "x", arg_two: "y")
      subject.do_delegated_thing
    end
  end
end

输出:

Bar
  calls Foo with expected arguments
  comparing double and instance_double
    calls double with unexpected arguments
    calls instance_double with unexpected arguments (FAILED - 1)

Failures:

  1) Bar comparing double and instance_double calls instance_double with unexpected arguments
     Failure/Error: expect(mock_baz_2).to receive(:do_thing).with(arg_one: "x", arg_two: "y")
       Missing required keyword arguments: arg_one_hundred
     # ./spec.rb:42:in `block (3 levels) in <top (required)>'
     # main.rb:22:in `<main>'

Finished in 0.00752 seconds (files took 0.0997 seconds to load)
3 examples, 1 failure