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.

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

J.