mockit.Delegate Maven / Gradle / Ivy

/*
 * Copyright (c) 2006 JMockit developers
 * This file is subject to the terms of the MIT license (see LICENSE.txt).
 */
package mockit;

/**
 * An empty interface to be used with the {@link Expectations#result} field or the
 * Invocations#with(Delegate) method, allowing test code to define varying invocation
 * results or argument matching rules, respectively.
 * 
 * When combined with the result field, a test will typically assign it with an anonymous class object implementing this interface
 * and containing a delegate method:
 * 
 *    new Expectations() {{
 *       mock.doSomething(anyInt, anyString);
 *       result = new Delegate() {
 *          String delegate(int i, String s) {
 *             return i > 0 ? s : "";
 *          }
 *       };
 *    }};
 *
 *    tested.exerciseCodeUnderTest();
 * 
 * The delegate class (either named or anonymous) must contain exactly one non-private instance method to be executed when the
 * mocked method or mocked constructor is invoked; it can contain any number of private or static methods, though.
 * The name of the delegate method can be anything.
 * Its parameters, however, should be the same as the parameters of the corresponding mocked method/constructor, or at least be compatible
 * with them.
 * Optionally, the delegate method can have an extra parameter of type {@link Invocation}, provided it appears as the first one.
 * The delegate method is also allowed to have no parameters (without counting the optional Invocation parameter).
 * 
 * When used with the result field, the result of a delegate method execution can be any return value compatible with the recorded
 * method's return type, or a thrown error/exception.
 * 

 * When used with the with(Delegate) method, the delegate method must return a boolean, being true for a
 * successfully matched argument or false otherwise.
 * 
 * Finally, note that a static method in the mocked type can have a delegate as well.
 * The same is true for private, final, and native methods.
 *
 * @see Tutorial
 *
 * @param  the type of the argument to be matched, when used with the with(Delegate) method
 */
public interface Delegate
{
}