mockit

Class MockUp<T>

java.lang.Object

mockit.MockUp<T>

Type Parameters:

T - specifies the type (class, interface, etc.) to be faked; multiple interfaces can be faked by defining a type variable in the test class or test method, and using it as the type argument; if a type variable is used and it extends a single type, then all implementation classes extending or implementing that base type are also faked; if the type argument itself is a parameterized type, then only its raw type is considered

public abstract class MockUp<T>
extends Object

A base class used in the creation of a mock-up for a class, an interface, etc. Such mock-ups can be used as fake implementations for use in unit or integration tests. For example:

 public final class FakeSystem extends MockUp<System> {
    @Mock public static long nanoTime() { return 123L; }
 }
 

One or more mock methods annotated as such must be defined in the concrete subclass. Each @Mock method should have a matching method or constructor in the faked class/interface. At runtime, the execution of a faked method/constructor will get redirected to the corresponding mock method.

When the faked type is an interface, an implementation class is generated where all methods are empty, with non-void methods returning a default value according to the return type: 0 for int, null for a reference type, and so on. In this case, an instance of the generated implementation class should be obtained by calling getMockInstance().

When the type to be faked is specified indirectly through a type variable, there are two other possible outcomes:

1. If the type variable "extends" two or more interfaces, a mock proxy class that implements all interfaces is created, with the proxy instance made available through a call to getMockInstance(). Example:

    @Test
    public <M extends Runnable & ResultSet> void someTest() {
        M mock = new MockUp<M>() {
           @Mock void run() { ...do something... }
           @Mock boolean next() { return true; }
        }.getMockInstance();
   
        mock.run();
        assertTrue(mock.next());
    }
    

2. If the type variable extends a single type (either an interface or a non-final class), then that type is taken as a base type whose concrete implementation classes should also get faked. Example:

    @Test
    public <BC extends SomeBaseClass> void someTest() {
        new MockUp<BC>() {
           @Mock int someMethod(int i) { return i + 1; }
        };
   
        int i = new AConcreteSubclass().someMethod(1);
        assertEquals(2, i);
    }
    

See Also:

MockUp(), MockUp(Class), MockUp(Object), getMockInstance(), onTearDown(), targetType, Tutorial

Field Summary

Fields

Modifier and Type	Field and Description
protected Type	targetType Holds the class or generic type targeted by this mock-up instance.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	MockUp() Applies the mock methods defined in the concrete subclass to the class or interface specified through the type parameter.
protected	MockUp(Class<?> targetClass) Applies the mock methods defined in the mock-up subclass to the given class/interface.
protected	MockUp(T targetInstance) Applies the mock methods defined in the mock-up subclass to the type specified through the type parameter, but only affecting the given instance.

Method Summary

Modifier and Type	Method and Description
T	getMockInstance() Returns the mock instance exclusively associated with this mock-up instance.
protected void	onTearDown() An empty method that can be overridden in a mock-up subclass that wants to be notified whenever the mock-up is automatically torn down.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

targetType

protected final Type targetType

Holds the class or generic type targeted by this mock-up instance.

Constructor Detail

MockUp

protected MockUp()

Applies the mock methods defined in the concrete subclass to the class or interface specified through the type parameter.

Throws:

IllegalArgumentException - if no type to be faked was specified; or if multiple types were specified through a type variable but not all of them are interfaces; or there is a mock method for which no corresponding real method or constructor is found; or the real method matching a mock method is abstract; or if an unbounded type variable was used as the base type to be faked

See Also:

MockUp(Class), MockUp(Object)

MockUp

protected MockUp(Class<?> targetClass)

Applies the mock methods defined in the mock-up subclass to the given class/interface.

In most cases, the constructor with no parameters can be used. This variation should be used only when the type to be faked is not accessible or known from the test code.

See Also:

MockUp(), MockUp(Object)

MockUp

protected MockUp(T targetInstance)

Applies the mock methods defined in the mock-up subclass to the type specified through the type parameter, but only affecting the given instance.

In most cases, the constructor with no parameters should be adequate. This variation can be used when mock data or behavior is desired only for a particular instance, with other instances remaining unaffected; or when multiple mock-up objects carrying different states are desired, with one mock-up instance per real instance.

If getMockInstance() later gets called on this mock-up instance, it will return the instance that was given here.

Parameters:

targetInstance - a real instance of the type to be faked, meant to be the only one of that type that should be affected by this mock-up instance; must not be null

See Also:

MockUp(), MockUp(Class)

Method Detail

getMockInstance

public final T getMockInstance()

Returns the mock instance exclusively associated with this mock-up instance. If the mocked type was an interface, then said instance is the one that was automatically created when the mock-up was applied. If it was a class, and no such instance is currently associated with this mock-up object, then a new uninitialized instance of the faked class is created and returned, becoming associated with the mock-up. If a regular initialized instance was desired, then the MockUp(Object) constructor should have been used instead.

In any case, for a given mock-up instance this method will always return the same mock instance.

Throws:

IllegalStateException - if called from a mock method for a static method, or if called on a mock-up whose base type was specified by a type variable

See Also:

Tutorial

onTearDown

protected void onTearDown()

An empty method that can be overridden in a mock-up subclass that wants to be notified whenever the mock-up is automatically torn down. Tear down happens when the mock-up goes out of scope: at the end of the test when applied inside a test, at the end of the test class when applied before the test class, or at the end of the test run when applied through the "mockups" system property.

By default, this method does nothing.