spock-spy-vs-mock

The main goal of this project is to show different approaches to stubbing in Spock
(spy vs mock).

preface

In general, difference between spy and mock is that the spy is always based on a real object,
and if we call a method that was not stubbed on spy it executes exactly like on a real object.

project description

The difference between spy and mock is clearly visible when it comes to
testing ArrayList:

• mock

  def "mock"() {
      given:
      def list = Mock(ArrayList) // compile error if Mock(new ArrayList())
  
      when:
      list.add(1)
  
      then:
      list.size() == 0
  }
  

• spy

  def "spy"() {
      given:
      def list = Spy(ArrayList) // or Spy(new ArrayList())
      
      when:
      list.add(1)
      
      then:
      list.size() == 1
  }