Re: [Mockobjects-java-users] how to use?

[Olaf K. <ok...@ab...>]

Oren Gross wrote:
> 
> If so, how can use mock objects for testing 
> objects that do not expect such an argument, 
> but create an instance of it inside?

Hi Oren,

probably the nicest thing in TestDrivenDevelopment is, that
the responsibility for creation of objects gets turned upside
down - or inside out if you prefer so... 

If you write Tests that want to parameterize an object with a
mock implementation you need a way to provide this from
outside. The bad way (but sometimes reasonable) would be to
"inject" a MockObject, using a method that is there only for
injecting it during the test run.
A probably better way would be to have the subsystem designed
in a way that they get their collaborators set from outside,
e.g. during creation in a factory or builder (or testcase).
You get this almost naturally with TestDrivenDevelopment
(http://c2.com/cgi/wiki?TestDrivenDevelopment).

In any case, you need to refactor the creation of the objects
to a place both the runtime- and the test-environment can
access.

One thing more: Beware of using MockObject to replace each and
every instance of collaborator interfaces in testing: You
might loose flexibility and the ability to refactor
mercilessly.
<shamelessAdvert>
  Beware of it even if there is a new version 
  of MockCreator available for Eclipse, VAJ and 
  CommandLine (www.abstrakt.de/mockcreator.html) 
  ;-)
</shamelessAdvert>
But of course, your milage may vary...

My advice is to get deep into TestDrivenDevelopment, this will
almost automagically lead to MockObjects at some point (if
this is not the way you went up to where you are now;-)

Olaf
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