From: jeem <jeem.hughes@...>
Date: 2005-03-15T23:00:21+09:00
Subject: Mocking new and other class methods

Hello group.  I wanted to be able to do something like this:

def testItResizesTheImage
  imageNew=ClassMethodMocker.new(Magick::Image,:new)
  image=FlexMock.new
  imageNew.handle { |imagePath| assert_equal(@imagePath,imagePage);
image }
  image.mock_handle(:somecall) { |etc| etc }
  # etc
  test_subj.doThatThing
  image.mock_verify
  imageNew.verify
end

So, I wrote a few loc to enable it (borrowing from FlexMock) for 'new'
calls at least.  I'm having second thoughts about how I implemented it,
so I was hoping some in the ng might want to kick it around.

My big concern with the current method (see below) is that the real new
might not be "put back" if a coder doesn't use MockNew.use.

I have other ways in mind to allow mocking of class methods, but they
all seem to put up new hoops for coders to jump through, and make the
resulting code less natural.

Here's the code, excluding the tests:

class Class
        public :alias_method
end

class Object
        def backupNew
                class << self
                        alias_method :mocknew_backedup_new, :new
                end
        end
        @@newHandler={}
        def delegateNew(newHandler)
                module_eval { @@newHandler[self]=newHandler; def
self.new(*args);
@@newHandler[self].handleNew(*args); end }
        end
        def restoreNew
                class << self
                        alias_method :new, :mocknew_backedup_new
                end
        end
end

class MockNew
        def initialize(klass,&block)
                klass.backupNew
                klass.delegateNew(self)
                @klass=klass
                @handlers=[]
                @callCount=0
                handle(&block) if block_given?
        end
        def handleNew(*args)
                result=@handlers[@callCount].call(*args)
                @callCount += 1
                restoreKlassNew if @callCoun...@handlers.length
                result
        end
        def restoreKlassNew
                @klass.restoreNew
        end
        def verify
                raise VerifyFailure.new, "Expected
#...@handlers.length}
cal...@handlers.length==1?'':'s'} to #{@klass}.new; received
#{@callCount}." unless @callCount == @handlers.length
        end

        def handle(&block)
                @handlers << block
        end
        def self.use(klass)
                mockNew=new(klass)
                yield mockNew
                mockNew.verify
        ensure
                mockNew.restoreKlassNew
        end
        class VerifyFailure < StandardError
        end
end