如何使用 Spock 模拟重载的 Java 方法

Question

I have a Java class MyClass with an overloaded method process:

class MyClass {
    private String process(String requestId, String request) {
       // Initial processing, creates processObject from request
       // then class actual processing:
       String temp = process ( processObject );
       // do stuff I want to test, generate response
       return response;
    };
    private String process( ProcessClass processObject ) {
       String result;
       // do actual processing of processObject
       return result;
    }
}

I want to test the first process() method using Spock. I am trying to use a Spy to mock the overloaded process(ProcessClass). Here's testProcess.groovy so far:

class TestProcessUsingString extends Specification {
   given:
      def testInput = "TestInput"
      def myObject = Spy(MyClass) {
         process(_ as ProcessClass) >> "My result string"
      }
   when:
      def response = myObject.process("TestInput")
      // Check response

This method does not work to mock the method process(ProcessClass...) as I would have expected. I have consulted http://spockframework.org/spock/docs/1.0/interaction_based_testing.html but I cannot figure it out.

How can I mock MyClass.process(ProcessClass) so that I can return a fake answer from it and pass it to the other process function?

Answer 1

Spock mocks, stubs and spies are based on Java or CGLIB dynamic proxies. Those in turn create subclasses suring runtime, overriding all public methods and hooking into them to provide the fancy features you need for mock testing. You however use private methods, which explains why this does not work. Furthermore, it is bad practice to test private methods and to use spies unless absolutely necessary. What makes it necessary to use a spy here?