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JMockit is a Java toolkit for automated developer testing.
It contains mocking/faking APIs and a code coverage tool, 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.
/*
* Copyright (c) 2006 Rogério Liesenfeld
* This file is subject to the terms of the MIT license (see LICENSE.txt).
*/
package mockit;
import java.lang.reflect.*;
import java.util.*;
import javax.annotation.*;
import static java.lang.reflect.Modifier.*;
import mockit.internal.classGeneration.*;
import mockit.internal.mockups.*;
import mockit.internal.startup.*;
import mockit.internal.state.MockClasses.*;
import mockit.internal.state.*;
import mockit.internal.util.*;
/**
* A base class used in the creation of a mock-up for a class or interface.
* Such mock-ups can be used as fake implementations for use in integration or unit tests.
*
* One or more mock methods annotated {@linkplain Mock as such} must be defined in the concrete subclass.
* Each {@code @Mock} method should have a matching method or constructor in the mocked class/interface.
* At runtime, the execution of a mocked 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: {@code 0} for {@code int}, {@code null} for a
* reference type, and so on.
* In this case, an instance of the generated implementation class should be obtained by calling
* {@link #getMockInstance()}.
*
* When the type to be faked is specified indirectly through a {@linkplain TypeVariable type variable}, there are two
* other possible outcomes:
*
* - If the type variable "
extends" two or more interfaces, a mocked proxy class that implements all
* interfaces is created, with the proxy instance made available through a call to {@link #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());
* }
*
*
* - If the type variable extends a single type (either an interface or a class), then that type is taken
* as a base type whose concrete implementation classes should also get mocked.
* 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);
* }
*
*
*
*
* @param 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
*
* @see #MockUp()
* @see #MockUp(Class)
* @see #MockUp(Object)
* @see #getMockInstance()
* @see #tearDown()
* @see #onTearDown()
* @see #mockedType
* @see Tutorial
*/
public abstract class MockUp
{
static { Startup.verifyInitialization(); }
/**
* Holds the class or generic type targeted by this mock-up instance.
*/
protected final Type mockedType;
@Nullable private final Class mockedClass;
@Nullable private Set> classesToRestore;
@Nullable private T mockInstance;
@Nullable T invokedInstance;
/**
* Applies the {@linkplain Mock 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 {@code abstract};
* or if an unbounded type variable was used as the base type to be faked
*
* @see #MockUp(Class)
* @see #MockUp(Object)
*/
protected MockUp()
{
validateMockingAllowed();
MockUp previousMockUp = findPreviouslyMockedClassIfMockUpAlreadyApplied();
if (previousMockUp != null) {
mockedType = previousMockUp.mockedType;
mockedClass = previousMockUp.mockedClass;
return;
}
mockedType = validateTypeToMock();
if (mockedType instanceof Class) {
@SuppressWarnings("unchecked") Class classToMock = (Class) mockedType;
mockedClass = redefineClassOrImplementInterface(classToMock);
}
else if (mockedType instanceof ParameterizedType) {
ParameterizedType parameterizedType = (ParameterizedType) mockedType;
@SuppressWarnings("unchecked") Class classToMock = (Class) parameterizedType.getRawType();
mockedClass = redefineClassOrImplementInterface(classToMock);
}
else {
Type[] typesToMock = ((TypeVariable) mockedType).getBounds();
if (typesToMock.length > 1) {
mockedClass = new MockedImplementationClass(this).createImplementation(typesToMock);
}
else {
mockedClass = new CaptureOfMockedUpImplementations(this, typesToMock[0]).apply();
}
}
}
private static void validateMockingAllowed()
{
if (TestRun.isInsideNoMockingZone()) {
throw new IllegalStateException("Invalid place to apply a mock-up");
}
}
@Nullable
private MockUp findPreviouslyMockedClassIfMockUpAlreadyApplied()
{
MockUpInstances mockUpInstances = TestRun.getMockClasses().findPreviouslyAppliedMockUps(this);
if (mockUpInstances != null) {
MockUp previousMockUp = mockUpInstances.initialMockUp;
if (mockUpInstances.hasMockUpsForSingleInstances()) {
return previousMockUp;
}
previousMockUp.tearDown();
}
return null;
}
@Nonnull
private Type validateTypeToMock()
{
Type typeToMock = getTypeToMock();
if (typeToMock instanceof WildcardType || typeToMock instanceof GenericArrayType) {
String errorMessage = "Argument " + typeToMock + " for type parameter T of an unsupported kind";
throw new UnsupportedOperationException(errorMessage);
}
else if (typeToMock instanceof TypeVariable) {
TypeVariable typeVar = (TypeVariable) typeToMock;
Type[] bounds = typeVar.getBounds();
if (bounds.length == 1 && bounds[0] == Object.class) {
throw new IllegalArgumentException("Unbounded base type specified by type variable \"" + typeVar + '"');
}
}
return typeToMock;
}
@Nonnull
private Type getTypeToMock()
{
Class currentClass = getClass();
do {
Type superclass = currentClass.getGenericSuperclass();
if (superclass instanceof ParameterizedType) {
return ((ParameterizedType) superclass).getActualTypeArguments()[0];
}
if (superclass == MockUp.class) {
throw new IllegalArgumentException("No type to be mocked");
}
currentClass = (Class) superclass;
}
while (true);
}
@Nonnull
private Class redefineClassOrImplementInterface(@Nonnull Class classToMock)
{
if (classToMock.isInterface()) {
return createInstanceOfMockedImplementationClass(classToMock, mockedType);
}
Class realClass = classToMock;
if (isAbstract(classToMock.getModifiers())) {
classToMock = new ConcreteSubclass(classToMock).generateClass();
}
classesToRestore = redefineMethods(realClass, classToMock, mockedType);
return classToMock;
}
@Nonnull
private Class createInstanceOfMockedImplementationClass(@Nonnull Class classToMock, @Nullable Type typeToMock)
{
return new MockedImplementationClass(this).createImplementation(classToMock, typeToMock);
}
@Nullable
private Set> redefineMethods(
@Nonnull Class realClass, @Nonnull Class classToMock, @Nullable Type genericMockedType)
{
if (TestRun.mockFixture().isMockedClass(realClass)) {
throw new IllegalArgumentException("Class already mocked: " + realClass.getName());
}
return new MockClassSetup(realClass, classToMock, genericMockedType, this).redefineMethods();
}
/**
* Applies the {@linkplain Mock 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 mocked is not accessible or known to the test.
*
* @see #MockUp()
* @see #MockUp(Object)
*/
protected MockUp(Class classToMock)
{
//noinspection ConstantConditions
if (classToMock == null) {
throw new IllegalArgumentException("Null reference when expecting the class to mock");
}
validateMockingAllowed();
mockedType = classToMock;
MockUp previousMockUp = findPreviouslyMockedClassIfMockUpAlreadyApplied();
if (previousMockUp != null) {
mockedClass = previousMockUp.mockedClass;
return;
}
if (classToMock.isInterface()) {
//noinspection unchecked
mockedClass = createInstanceOfMockedImplementationClass((Class) classToMock, classToMock);
}
else {
mockedClass = classToMock;
//noinspection unchecked
Class realClass = (Class) classToMock;
classesToRestore = redefineMethods(realClass, realClass, null);
mockInstance = null;
}
}
/**
* Applies the {@linkplain Mock 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 to be mocked.
*
* If {@link #getMockInstance()} later gets called on this mock-up instance, it will return the instance that was
* given here.
*
* @param instanceToMock 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 {@code null}
*
* @see #MockUp()
* @see #MockUp(Class)
*/
protected MockUp(T instanceToMock)
{
//noinspection ConstantConditions
if (instanceToMock == null) {
throw new IllegalArgumentException("Null reference when expecting the instance to mock");
}
validateMockingAllowed();
MockUp previousMockUp = findPreviouslyMockedClassIfMockUpAlreadyApplied();
if (previousMockUp != null) {
mockedType = previousMockUp.mockedType;
mockedClass = previousMockUp.mockedClass;
return;
}
@SuppressWarnings("unchecked") Class classToMock = (Class) instanceToMock.getClass();
mockedType = classToMock;
mockedClass = classToMock;
classesToRestore = redefineMethods(classToMock, classToMock, classToMock);
setMockInstance(instanceToMock);
}
private void setMockInstance(@Nonnull T mockInstance)
{
TestRun.getMockClasses().addMock(this, mockInstance);
this.mockInstance = mockInstance;
}
/**
* 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 {@link #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 Tutorial
*/
public final T getMockInstance()
{
if (invokedInstance == Void.class) {
throw new IllegalStateException("Invalid attempt to get mock instance from inside static mocked method");
}
if (mockedType instanceof TypeVariable && ((TypeVariable) mockedType).getBounds().length == 1) {
throw new IllegalStateException("No single instance applicable when faking all classes from a base type");
}
if (invokedInstance != null) {
return invokedInstance;
}
if (mockInstance == null && mockedClass != null) {
Object newInstance;
if (GeneratedClasses.isGeneratedImplementationClass(mockedClass)) {
newInstance = GeneratedClasses.newInstance(mockedClass);
}
else if (Proxy.isProxyClass(mockedClass)) {
newInstance = MockInvocationHandler.newMockedInstance(mockedClass);
}
else {
newInstance = ConstructorReflection.newUninitializedInstance(mockedClass);
}
//noinspection unchecked
setMockInstance((T) newInstance);
}
//noinspection ConstantConditions
return mockInstance;
}
/**
* Discards the mock methods originally applied by instantiating this mock-up object, restoring faked methods to
* their original behaviors.
*
* This method should rarely, if ever, be used, since tear-down is automatic: all classes faked by a test
* will automatically be restored at the end of the test; the same for classes faked for the whole test class in a
* "before class" method.
*
* @see #onTearDown()
*/
public final void tearDown()
{
MockUpInstances mockUpInstances = TestRun.getMockClasses().removeMock(this, mockInstance);
if (!mockUpInstances.hasMockUpsForSingleInstances() && classesToRestore != null) {
TestRun.mockFixture().restoreAndRemoveRedefinedClasses(classesToRestore);
classesToRestore = null;
}
}
/**
* An empty method that can be overridden in a mock-up subclass wanting to be notified on tear down; this happens
* through automatic tear down, but not if {@link #tearDown()} is called.
*
* By default, this method does nothing.
*/
protected void onTearDown() {}
}