Improve spy error message when constructor args dont match

[robfletcher]

Originally reported on Google Code with ID 277

1. Create some spy like: Spy(Foo, constructorArgs: 'foo')
2. If Foo class does not have any constructor then:

java.lang.ClassCastException
    at java.lang.Class.cast(Class.java:2990)
    at org.spockframework.mock.runtime.MockConfiguration.getOption(MockConfiguration.java:92)
    at org.spockframework.mock.runtime.MockConfiguration.<init>(MockConfiguration.java:46)
    at org.spockframework.lang.SpecInternals.createMock(SpecInternals.java:47)
    at org.spockframework.lang.SpecInternals.createMockImpl(SpecInternals.java:282)
    at org.spockframework.lang.SpecInternals.SpyImpl(SpecInternals.java:171)
    at org.gradle.execution.ExcludedTaskFilteringBuildConfigurationActionTest.$spock_initializeFields(ExcludedTaskFilteringBuildConfigurationActionTest.groovy:30)

Reported by szczepiq on 2012-10-23 09:03:45

[robfletcher]

The problem here is not the actual ctor args, but that you are supposed to pass a List
to "constructorArgs:". (I'd expect a better message otherwise.) That said, maybe we
shouldn't cast to List but use Groovy iteration semantics instead.

Reported by pniederw on 2012-10-23 09:25:22