RFC Mocking an Accessor with Test::MockObject

[ait]

I wanted to write a tutorial for this but probably this needs some more work or maybe there is already a known a better way to do this. I was actually surprised that Test::MockObject had no apparent easy way to emulate accessors, at least it was not obvious from the pod

The thing is that when testing complex Moose stuff I found myself having to mock quite a few objects and their getters and setters so I came up with a simple method of using global variables in the test script and mocking the getters and setters to them.

Comments welcome to see if it's worth anything for a tutorial, or comments on how to better do this!

# Setup the mockery
my $entity = Test::MockObject->new();
$entity->fake_module('foo::entity');
my $error = undef;
$entity->mock('error',sub {shift; &mock_accessor_var(\$error,@_)});
my $reqbody = undef;
$entity->mock('reqbody',sub {shift; &mock_accessor_var(\$reqbody,@_)})
+;

# Do the tests
$entity->reqbody('blah');
my $r = $reqproc->decode($entity);
ok(!$r, 'Bad request expected to fail');
ok($entity->error eq 'XDOMERR', 'Got XDOMERR');

# the accessor to var mocker
sub mock_accessor_var {
  my $var = shift;
  if(@_){
    $$var = shift;
  }
  else{
    return $$var;
  }
}

[chromatic]

If I were to write T::MO again, I'd write Test::MockObject::Extends first, then perhaps generalize to T::MO. The less you need to mock, the better your tested API and the more robust your tests.

If you have to mock an accessor, you're probably mocking too much.

[ait]

Yeah well every case is different IMHO. This test code is for a specific component a relatively complex Catalyst Model (that is modeled as an aggregate), so I wanted to test very specific classes that receive complex objects and Catalyst Model instances as well. Creating the actual objects would have been a real pain and I wanted to write unit tests for every single component. I looked into Test::MockObject::Extends but it was more than I needed (and virtually impossible and useless to instantiate the whole model to test such a small class), so I settled for the solution above.

Do you think it's worth a tutorial? Is the title appropriate? I could start the article with your caveat above ;-) ("If you have to mock an accessor, you're probably mocking too much.")

[chromatic]

I'm always interested in more testing articles, especially for sites like Perl.com.