我如何在 minitest 中模拟一个块？

Question

希望对 MiniTest 人员来说是一个简单的问题..

我有一段代码，我将在这里浓缩成一个例子：

class Foo
  def initialize(name)
    @sqs    = Aws::SQS::Client.new
    @id     = @sqs.create_queue( queue_name: name ).fetch(:queue_url)
    @poller = Aws::SQS::QueuePoller.new(@id)
  end
  def pick_first
    @poller.poll(idle_timeout: 60) do |message|
      process_msg(message) if some_condition(message)
    end
  end

我怎样才能 mock/stub/something-else 才能让 message 通过 some_condition() 测试并可能用 process_msg() 处理？

即我想测试 @poller.poll(idle_timeout: 60) do |message|.

我试图用模拟轮询器对 Aws::SQS::QueuePoller#new 进行存根，但它不会将消息生成给 |message| 只是返回它..

这是我的，不工作：

mockqueue = MiniTest::Mock.new

mocksqs = MiniTest::Mock.new
mocksqs.expect :create_queue, mockqueue, [Hash]

mockpoller = MiniTest::Mock.new                                                                                                                         
mockpoller.expect :poll, 'message', [{ idle_timeout: 60 }]

Aws::SQS::Client.stub :new, mocksqs do
  Aws::SQS::QueuePoller.stub :new, mockpoller do
    queue = Foo.new(opts)
    queue.pick_first
  end
end

如果我在 #pick_first 中收到一个变量，那就是 mock 放置它的地方，而不是 |message|:

def pick_first
    receiver = @poller.poll(idle_timeout: 60) do |message|
      process_msg(message) if some_condition(message)
    end
    puts receiver # this shows my 'message' !!! WHYYYY??
  end

Answer 1

回答我自己的问题，以防其他人有同样的问题。

我通过 Twitter 寻求帮助，MiniTest 的作者 Ryan Davis（又名 github 上的@zenspider / Twitter 上的@the_zenspider）给出了一个快速的答复和邀请将问题提交给 MiniTest github 问题跟踪器。

I did so，并从 Ryan 和 Pete Higgins（github 上的@phiggins）那里得到了一些很好的回应，我在这里完整地复制了这些回应。感谢两位的帮助！

@phiggins 说：

What about something like:

class Foo   def initialize(name, opts={})
  @sqs    = Aws::SQS::Client.new
  @id     = @sqs.create_queue( queue_name: name ).fetch(:queue_url)
  @poller = opts.fetch(:poller) { Aws::SQS::QueuePoller.new(@id) }   end

  def pick_first
    @poller.poll(idle_timeout: 60) do |message|
    process_msg(message) if some_condition(message)
    end
  end
end

# later, in your tests
describe Foo do
  it "does the thing in the block" do
  # could be moved into top-level TestPoller, or into shared setup, etc.
  poller = Object.new
  def poller.poll(*) ; yield ; end

  foo = Foo.new("lol", :poller => poller)
  foo.pick_first

  assert foo.some_state_was_updated
  end
end

@zenspider 说：

NOTE: I'm anti-mock. I'm almost anti-stub for that matter. IMHO, if you can't test something without mocking it, you probably have a design issue. Calibrate accordingly against the text below.

I suggested using Liskov Substitution Principal (LSP) because I was focused on testing that process_msg did the right thing in that context. The idea is simple, subclass, override the method in question, and use the subclass within the tests. LSP says that testing a subclass is equivalent to testing the superclass.

In the case of the polling object, you have three concerns (polling, filtering, and processing) going on in that method, one of whom you shouldn't be testing (because it is third-party code). I'd refactor to something like this:
class Foo
  # ....

  def poll
    @poller.poll(idle_timeout: 60) do |message|
      yield message
    end
  end

  def pick_first
    poll do |message|
      process_msg(message) if some_condition(message)
    end
  end
end
Then testing is a simple matter:
class TestFoo1 < Foo
  def poll
    yield 42 # or whatever
  end

  # ...
end

# ...

assert_equal 42, TestFoo1.new.pick_first # some_condition truthy
assert_nil       TestFoo2.new.pick_first # some_condition falsey
There are shorter/"rubyier" ways to do this, but they're equivalent to the above and the above illustrates the point better.

Answer 2

我试图对产生块的东西进行存根，但找不到答案。（不确定这是否正是您要问的。）这是操作方法。

这是我们要模拟的 class：

class Foo
  def bar
    yield(42)
  end
end

在我们的测试中，我们实例化我们的对象：

foo = Foo.new

然后我们可以用 Ruby 覆盖这个方法来做其他事情：

def foo.bar
  yield(16)
end

现在当我们调用它时，它会调用存根版本：

foo.bar do |value|
  puts value
  # => 16
end

很简单。这花了我一段时间才弄清楚。希望这对某人有所帮助:)

我如何在 minitest 中模拟一个块？

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unit-testing

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minitest