ruby - RSpec - 如何测试对象是否在 #initialize 中向自身发送消息

Question

读完这个问题后，我真的不喜欢这个答案。

Rails / RSpec: How to test #initialize method?

也许我遇到了第三种情况。这就是我现在所拥有的，受到该答案中第二个代码的启发。

# Picture is collection of SinglePictures with same name and filename,
# but different dimensions
class Picture
  attr_accessor :name, :filename
  attr_reader :single_pics, :largest_width

  def initialize(name, filename, dimensions=nil)
    @largest_width = 0
    @single_pics = {}
    add_single_pics(dimensions) if dimensions
  end

  def add_single_pics(max_dimension)
    # logic
  end
end

describe '#initialize' do
  it 'should not call add_single_pics if dimensions is not given' do
    subject = Picture.new('Test Picture', 'Test-Picture')
    expect(subject.largest_width).to eq 0
  end

  it 'should call add_single_pics if dimensions are given' do
    subject = Picture.new('Test Picture', 'Test-Picture', 1920)
    expect(subject.largest_width).to eq 1920
  end
end

我真的不喜欢这个，因为我正在 #initialize 测试中测试 add_single_pics 的功能。我想在规范中以某种方式写下这个:

  expect(subject).not_to have_received(:add_single_pics)
  expect(subject).to have_received(:add_single_pics)

但我明白了

Expected to have received add_single_pics, but that object is not a spy
or method has not been stubbed.

我能以某种方式解决这个问题吗？

Answer 1

Spies are an alternate type of test double that support this pattern by allowing you to expect that a message has been received after the fact, using have_received.

https://relishapp.com/rspec/rspec-mocks/v/3-5/docs/basics/spies

只有 spy 对象可以存储方法调用。要按照您想要的方式测试您的真实类，您必须在初始化类之前使用 expect_any_instance_of 语句:

expect_any_instance_of(Picture).to receive(:add_single_pics)
Picture.new('Test Picture', 'Test-Picture')

在这种情况下，您的 add_single_pics 方法将被调用，但其逻辑不会运行，如果您需要运行它，您需要调用 and_call_original 方法匹配器:

expect_any_instance_of(Picture).to receive(:add_single_pics).and_call_original