ruby - 如何避免使用 allow_any_instance_of？

Question

假设我们有以下代码:

class A
  def create_server
    options = {
      name: NameBuilder.new.build_name
    }
    do_some_operations(options)
  end
end

为了测试这些方法，我曾经使用allow_any_instance_of:

it 'does operations' do
  allow_any_instance_of(NameBuilder).to receive(:build_name)
  # test body
end

但是文档建议我们不要使用它because of several reasons .那么如何避免 allow_any_instance_of 呢？我只有一个解决方案:

class A
  def create_server
    options = {
      name: builder.build_name
    }
    do_some_operations
  end

  private

  def builder
    NameBuilder.new
  end
end

但是使用这种方法，代码很快就会充满几乎无用的方法(尤其是当您在所描述的类中积极使用不同对象的组合时)。

Answer 1

根据 Uzbekjon's answer 没有依赖注入(inject)(我同意)您还可以考虑取消对 NameBuilder.new 的调用，这样您就可以直接控制被测 NameBuilder 的实例:

class NameBuilder
  def build_name
    # builds name...
  end
end

class A
  def create_server
    options = {
      name: NameBuilder.new.build_name
    }
    do_some_operations(options)
  end

  def do_some_operations(options)
    # does some operations
  end
end

RSpec.describe A do
  let(:a) { described_class.new }

  describe '#create_server' do
    let(:name_builder) { instance_double(NameBuilder) }

    before do
      allow(NameBuilder).to receive(:new).and_return(name_builder)
    end

    it 'does operations' do
      # the first expectation isn't really part of what you seem
      # to want to test, but it shows that this way of testing can work
      expect(name_builder).to receive(:build_name)
      expect(a).to receive(:do_some_operations)
      a.create_server
    end
  end
end