使用RSpec测试警告

Question

是否有可能使用RSpec测试Ruby的警告？

像这样:

class MyClass
  def initialize
    warn "Something is wrong"
  end
end

it "should warn" do
  MyClass.new.should warn("Something is wrong")
end

Answer 1

warn定义在Kernel,包含在每个对象中.如果您在初始化期间未提出警告,则可以指定如下警告:

obj = SomeClass.new
obj.should_receive(:warn).with("Some Message")
obj.method_that_warns

在initialize方法中引发警告的指标要复杂得多.如果必须这样做,您可以交换假IO对象$stderr并进行检查.请务必在示例后恢复它

class MyClass
  def initialize
    warn "Something is wrong"
  end
end

describe MyClass do
  before do
    @orig_stderr = $stderr
    $stderr = StringIO.new
  end

  it "warns on initialization" do
    MyClass.new
    $stderr.rewind
    $stderr.string.chomp.should eq("Something is wrong")
  end

  after do
    $stderr = @orig_stderr
  end
end

Answer 2

有一篇关于自定义期望的好文章可以解决您的问题:http://greyblake.com/blog/2012/12/14/custom-expectations-with-rspec/

所以它想:

expect { MyClass.new }.to write("Something is wrong").to(:error)

根据该文章,您可以创建自己的期望,使用它像这样:

expect { MyClass.new }.to warn("Something is wrong")