Automocked objects

Ovid has asked for the wisdom of the Perl Monks concerning the following question:

So I have some code I'm testing which relies on a class with a whole bunch of niggling, annoying little methods getting called hither and yon. For the purposes of my tests, however, I really only care about one accessor at the end of the test and what it returns (since some methods are called in void context). I don't care to go through the trouble of mocking all of the other methods. I'm looking for (and can't find) a test version of Class::BlackHole. I'm thinking something like this:

  use Test::Automock;
  my $mock = Test::Automock->('Some::Difficult::Module');
  $mock->add( fetch_my_slippers => sub { 1 } );  # adds this method

  can_ok $object, 'stuff';
  ok $object->stuff, '... and calling it should succeed';

  my @expected = (
    fribble => [ $mock, $object ],
    woobie  => [ $mock ],
  );
  is_deeply $mock->methods_called, \@expected,
    "... with Some::Difficult::Methods doing their thing";
  $mock->reset;
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Test::Automock would simply use autoload to capture all method calls and their arguments. Methods by default would return a true value unless specifically overridden. I'd have to do tricks like overriding isa() and friends, but that seems like it would be a very lightweight method of handling mocked objects.

Is there something which does this? Did I miss anything?

Cheers,
Ovid

New address of my CGI Course.

Comment on Automocked objects Download Code

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Re: Automocked objects
by jasonk (Parson) on Apr 17, 2007 at 12:00 UTC

I do this by subclassing Test::MockObject...

package Test::AutoMock;
use base 'Test::MockObject';

# This is a stripped-down version of some of my own testing
# code, so this is untested, but should work...
sub dispatch_mocked_method {
    my $self = $_[0];
    my $sub = splice( @_, 1, 1 );
    my $subs = Test::MockObject::_subs( $self );
    $self->log_call( $sub, @_ );

    if ( exists $subs->{ $sub } ) {
        goto &{ $subs->{ $sub } };
    } else {
        return 1;
    }
}
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dispatch_mocked_method is called by Test::MockObject::AUTOLOAD, and carps when you call a method that hasn't been mocked, so if you just replace the carp with a return 1; you get the 'return true unless overridden' behaviour. I also moved the log call outside the if, so that the call log can include both mocked and default method calls.

We're not surrounded, we're in a target-rich environment!

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Re: Automocked objects (chains)
by tye (Sage) on Apr 17, 2007 at 16:01 UTC

If you make a module out of this, it might be best to use the object itself as the default "true" return value. That way chained method calls will work.

- tye

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