Spock specification for testing partial mocking of abstract classes

PartialMockingAbstractClasses.groovy

import spock.lang.Specification

class PartialMockingAbstractClasses extends Specification {
	def "Square with stubbed getLength()"() {
		given:
		Square square = Spy() {
		  2 * getLength() >> 3
		}
		when:
		def area = square.area
		then:
		area == 9
	  }
}

Square.java

public abstract class Square {
  public abstract double getLength();

  public double getArea() {
    return getLength() * getLength();
  }
}