CodeConstraintVerificationSpec.groovy

import spock.lang.Specification

class CodeConstraintVerificationSpec extends Specification {
	def repository = Mock(List)
	def service = new Service(repository)

	def "failing test"() {
		given:
			def entity = new Entity(events: ['test'])
		when:
			service.save(entity)
		then:
			1 * repository.add({ Entity e ->
				println(e.events)
				e.events.any { it == 'test' }
			} as Entity)
	}

	static class Service {
		List<Entity> repository

		Service(List<Entity> repository) {
			this.repository = repository
		}

		void save(Entity entity) {
			repository.add(entity)
		}
	}

	static class Entity {
		def events = new ArrayList<>()
	}
}

output.txt

[test]
[test]
[test]
[test]
[test]

Too few invocations for:

1 * repository.add({ Entity e ->
				println(e.events)
				e.events.any { it == 'test' }
			} as Entity)   (0 invocations)

Unmatched invocations (ordered by similarity):

1 * repository.add(<Test$Entity@71def8f8 events=[test]>)
One or more arguments(s) didn't match:
0: Condition not satisfied:
   
   e.events.any { it == 'test' }
   | |      |
   | [test] false
   <Test$Entity@71def8f8 events=[test]>