Validation of parameter passed to mock call in Spock

If you use Spock, sometimes you want to check mock method call. You can of course do it like this:
Problem here is that when the parameter passed to the method is wrong, you won't know what is wrong with it:

Too few invocations for:

1 * service.method({
            it.firstname == "Peter" && it.surname == "Stawicki"
        })   (0 invocations)

Unmatched invocations (ordered by similarity):

1 * service.method(eu.vegasoft.spocktest.validateparam.Person@40f892a4)

Sometimes we want to validate also parameter passed to the mock method. We can do it like this:
Now when the passed parameter does not match, we can see exactly what was wrong with it:

Condition not satisfied:

p.firstname == "Peter"
| |         |
| Paweł     false
|           3 differences (40% similarity)
|           P(aw)e(ł)
|           P(et)e(r)
eu.vegasoft.spocktest.validateparam.Person@34b23d12