From: Robert Klemme <bob.news@...>
Date: 2005-03-16T00:25:23+09:00
Subject: Re: Mocking new and other class methods


"jeem" <jeem.hughes@gmail.com> schrieb im Newsbeitrag
news:1110898032.514026.227640@f14g2000cwb.googlegroups.com...
> Let me try again.
>
> class CodeIWantToTest
> def foo(bar)
>   f = File.new(@userPath+bar)
>   #more
>   f.close
> end
> end
>
> class Tests < Test::Unit::TestCase
> def testFoo
>    fileNew=MockNew.new(File)
>    mockFile=FlexMock.new
>    fileNew.handle { |path| assert_equal('/home/usrname/etc/bob',path);
> mockFile }
>    #more
>    subj.foo('bob')
>    fileNew.verify
> end
> end
>
> I the test above, I want foo to call File.new.  If I were to make a
> mock class (cl_fake) in my test, I couldn't expect foo to call it,
> because foo is not aware of cl_fake.  Foo knows about File.

Ah, ok.  Thx for clarifying.

> Maybe I'm missing something.  Can you write the example above with the
> method from your post?

Well, you had to redefine constant File, which might not be such a good
idea.

Then what about a transaction based approach?  Like

module Kernel
private
  def mock(obj, sym, mock)
    cl = class <<obj; self; end
    old = obj.method sym
    cl.class_eval { define_method(sym, &mock) }

    begin
      yield
    ensure
      cl.class_eval { define_method(sym, &old) }
    end
  end
end

>> mock File, :new, lambda {|*f| "new! #{f.inspect}"} do
?>   File.new "foo", "r"
>> end
=> "new! [\"foo\", \"r\"]"

You can even nest that:

>> mock File, :new, lambda {|*f| "new! #{f.inspect}" } do
?>   p File.new( "foo", "r" )
>>
?>   mock File, :new, lambda {|*f| "new 2: #{f.inspect}" } do
?>     p File.new( "bar", "w" )
>>   end
>>
?>   p File.new( "foo", "r" )
>> end
"new! [\"foo\", \"r\"]"
"new 2: [\"bar\", \"w\"]"
"new! [\"foo\", \"r\"]"
=> nil

Kind regards

    robert