Test Showing Why "as" operator is important

SomethingTests.groovy

package com

import grails.test.GrailsUnitTestCase;
import com.SomeService

class SomethingTests extends GrailsUnitTestCase {

	void testSomething() {
		Something thing = new Something()
//		thing.someService = [ get : { a -> throw new Throwable() } ]  as SomeService // works
		thing.someService = [ get : { a -> throw new Throwable() } ] // need the "as" operator!
		
		assert thing.methodWeAreTesting()
	}
	
}