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JMockit is a Java toolkit for developer (unit/integration) testing. It contains mocking APIs and other tools, supporting both JUnit and TestNG. The mocking APIs allow all kinds of Java code, without testability restrictions, to be tested in isolation from selected dependencies.
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/*
 * Copyright (c) 2006-2012 Rogério Liesenfeld
 * This file is subject to the terms of the MIT license (see LICENSE.txt).
 */
package mockit;

import java.lang.annotation.*;

/**
 * Indicates an instance field or test method parameter of a mocked type whose value will be
 * a mocked instance.
 * Such fields or parameters can be of any type, except for primitive and array types.
 * The declared type of the mock field or mock parameter is the mocked type (unless
 * {@linkplain #realClassName specified otherwise}).
 * 
 * For the duration of each test where the mocked type is in scope, all new instances of that type, as well as those
 * previously created, will also be mocked.
 * Static methods and constructors belonging to a mocked class type are mocked as well, just like
 * instance methods.
 * Static class initializers (including assignments to static fields) of a mocked class are not
 * stubbed out by default, but they will be if {@linkplain #stubOutClassInitialization specified}.
 * 

 * In the case of an instance field, it can be declared in a test class, in a super-class of a test class, or in an
 * {@link Expectations} subclass.
 * In the case of a parameter, it can only be declared in a test method.
 * 

 * Notice that not only a concrete {@code Expectations} subclass used in specific tests can declare mock fields, but
 * also any intermediate super-class in the inheritance hierarchy from {@code Expectations} to the "final" subclass.
 * This can be used to define reusable {@code Expectations} subclasses, containing mock fields that are common to a
 * whole group of tests.
 * 

 * Note also that for inner {@code Expectations} subclasses the full set of mock fields will consist of the local
 * "inner" fields plus any fields declared in the test class.
 * This can be used to declare mock fields that are common to all tests in the class, even though some of these tests
 * may define additional mock fields in specific {@code Expectations} subclasses.
 * The same applies to mock parameters declared for the test method.
 * 

 * Therefore, there are three possible scopes for mocked types, from larger to smaller: the whole test class, the test
 * method, and the expectation block inside the test method. Some tests will use only one or two of these scopes, while
 * others can take advantage of all three.
 * 

 * Usually, a mocked instance gets created and assigned to a declared mock field automatically, without the test code
 * having to do anything.
 * It is also possible, however, for the test itself to provide this instance, by declaring the field as {@code final}
 * and assigning to it the desired instance.
 * If no such instance is necessary because only static methods or constructors will be called, then this final field
 * can receive the {@code null} reference.
 * Mock parameters, on the other hand, will always receive a mocked argument whenever the test method is executed by the
 * test runner.
 * 

 * For each mocked type there is at least one target class for mocking, which is derived from the declared type
 * of the mock field or parameter, or specified through an annotation attribute.
 * By default, all methods (including those which are {@code static}, {@code final}, {@code private}, {@code abstract},
 * or {@code native}) and constructors in the target classes will be mocked.
 * 

 * When a method or constructor is mocked, any invocations will not result in the execution of the original code, but
 * only in a call back to JMockit; according to the current phase of execution for the test - record,
 * replay, or verify - the appropriate action (do nothing, return a recorded value, etc.) will be
 * taken.
 * 

 * The following rules are applied when deriving target classes from the mocked type:
 * 

 * The type is a concrete or enum class: this class and all its super-classes up to but excluding
 * {@code java.lang.Object} will be the target classes for mocking.
 * The type is an interface or annotation: a
 * {@linkplain java.lang.reflect.Proxy dynamic proxy class} is created and used as the only target.
 * 
 * The type is an abstract class: a concrete subclass is generated with mock implementations for the
 * abstract methods in that class and in all of its super-classes (again, excluding {@code Object}); these super-classes
 * are also targeted for mocking of non-abstract methods and constructors.
 * 
 * In the
 * Tutorial
 *
 * @see #methods methods
 * @see #inverse inverse
 * @see #stubOutClassInitialization stubOutClassInitialization
 * @see #realClassName realClassName
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.PARAMETER})
public @interface Mocked
{
   /**
    * Same as specifying only the {@link #methods methods} attribute.
    */
   String[] value() default {};

   /**
    * One or more mock filters.
    * Given a target class for mocking, only those methods and constructors which match at least one filter will be
    * mocked.
    * 
    * If no other annotation attribute needs to be specified for a given mocked type, then for convenience the value for
    * this attribute can also be specified through the default {@link #value value} attribute, that is, by just
    * supplying the list of mock filters without naming any annotation attribute.
    * 

    * Each mock filter must follow the syntax {@code [nameRegex][(paramTypeName...)]}, where
    * {@code nameRegex} is a {@linkplain java.util.regex.Pattern regular expression} for matching method names, and
    * {@code paramTypeName} is the name of a primitive or reference parameter type (actually, any suffix of the type
    * name is enough, like "String" instead of the full class name "java.lang.String").
    * If {@code nameRegex} is omitted the filter matches only constructors.
    * If {@code (paramTypeName...)} is omitted the filter matches methods with any parameters.
    * 

    * If no filters are specified, then all methods and constructors declared in the target class are mocked, and all
    * static initializers are stubbed out.
    * 

    * A filter containing just the empty string matches no methods, no constructors, and no static initializers
    * of the target class; this can be used to obtain a mocked instance where no executable code is actually mocked or
    * stubbed out.
    * 

    * The special filter {@code ""} can be used to match the static initializers of the target class.
    * If only this filter is specified then the static initializers are stubbed out and no methods or constructors are
    * mocked; the opposite can be achieved by using the {@link #inverse inverse} attribute.
    */
   String[] methods() default {};

   /**
    * Indicates whether the mock filters are to be inverted or not.
    * If inverted, only the methods and constructors matching them are not mocked.
    */
   boolean inverse() default false;

   /**
    * Indicates whether static initialization code in the mocked class should be stubbed out or not.
    * Static initialization includes the execution of assignments to static fields of the class and the execution of
    * static initialization blocks, if any.
    * (Note that {@code static final} fields initialized with compile-time constants are not assigned at
    * runtime, remaining unaffected whether the class is stubbed out or not.)
    * 

    * By default, static initialization code in a mocked class is not stubbed out.
    * The JVM will only perform static initialization of a class once, so stubbing out the initialization code
    * can have unexpected consequences.
    * Static initialization will occur the first time the class is instantiated, has a static method called on it, or
    * has a static field whose value is defined at runtime accessed; these are the only events which prompt the JVM to
    * initialize a class.
    * If the original class initialization code was stubbed out, then it will not be there to be executed at the time of
    * static initialization, potentially leaving static fields {@code null} and later causing
    * {@code NullPointerException}'s to occur.
    */
   boolean stubOutClassInitialization() default false;

   /**
    * Specify the fully qualified name of the concrete class to be considered as the mocked type when it cannot be used
    * as the declared type, and the instance automatically created by JMockit for a super-type wouldn't be appropriate
    * for the test.
    * 
    * Note that this attribute can also be used when the desired concrete class is not accessible to the test (for
    * example, if it's a private inner class inside the code under test).
    *
    * @see Expectations#newInstance(String, Class[], Object...)
    */
   String realClassName() default "";
}