tessl/maven-org-mockito--mockito-core

Mockito mock objects library core API and implementation for comprehensive Java unit testing

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Mock Creation and Configuration

Name: tessl/maven-org-mockito--mockito-core
Author: tessl

This section covers creating and configuring mock objects, spies, and advanced mock settings in Mockito.

Basic Mock Creation

Creating Mocks

Create mock instances of classes or interfaces.

public static <T> T mock(Class<T> classToMock)
public static <T> T mock(Class<T> classToMock, String name)
public static <T> T mock(Class<T> classToMock, Answer defaultAnswer)
public static <T> T mock(Class<T> classToMock, MockSettings settings)

// Parameterless mock creation (since 4.10.0)
public static <T> T mock(T... reified)
public static <T> T mock(Answer defaultAnswer, T... reified)
public static <T> T mock(String name, T... reified)
public static <T> T mock(MockSettings settings, T... reified)

Usage Examples:

// Basic mock creation
List<String> mockList = mock(List.class);
UserService mockUserService = mock(UserService.class);

// Named mock for better error messages
List<String> namedMock = mock(List.class, "userList");

// Mock with custom default answer
List<String> mockWithAnswer = mock(List.class, RETURNS_SMART_NULLS);

// Parameterless mock creation (automatic type detection)
List<String> autoMock = mock();
UserService autoUserService = mock();

// Parameterless with custom settings
List<String> customAutoMock = mock(RETURNS_SMART_NULLS);
List<String> namedAutoMock = mock("myList");

Creating Spies

Create spies that wrap real objects, calling real methods unless stubbed.

public static <T> T spy(T object)
public static <T> T spy(Class<T> classToSpy)

// Parameterless spy creation (since 4.10.0)
public static <T> T spy(T... reified)

Usage Examples:

// Spy on existing object
List<String> realList = new ArrayList<>();
List<String> spyList = spy(realList);

// Spy on class (calls real constructor)
List<String> classSpy = spy(ArrayList.class);

// Parameterless spy creation (automatic type detection)
List<String> autoSpy = spy();

// Partial stubbing with spy
when(spyList.size()).thenReturn(100);
spyList.add("real method called");

Mock Settings and Configuration

MockSettings Interface

Advanced configuration for mock creation.

public static MockSettings withSettings()

interface MockSettings {
    MockSettings name(String name);
    MockSettings defaultAnswer(Answer defaultAnswer);
    MockSettings extraInterfaces(Class<?>... interfaces);
    MockSettings serializable();
    MockSettings serializable(SerializableMode mode);
    MockSettings spiedInstance(Object spiedInstance);
    MockSettings useConstructor(Object... constructorArgs);
    MockSettings outerInstance(Object outerClassInstance);
    MockSettings strictness(Strictness strictness);
    MockSettings mockMaker(String mockMaker);
    @Deprecated MockSettings lenient();
    MockSettings invocationListeners(InvocationListener... listeners);
    MockSettings verificationStartedListeners(VerificationStartedListener... listeners);
    MockSettings stubbingLookupListeners(StubbingLookupListener... listeners);
    MockSettings stubOnly();
    MockSettings withoutAnnotations();
    MockSettings verboseLogging();
    MockSettings genericTypeToMock(Type genericTypeToMock);
    <T> MockCreationSettings<T> build(Class<T> typeToMock);
    <T> MockCreationSettings<T> buildStatic(Class<T> classToMock);
}

Usage Examples:

// Mock with multiple interfaces
Foo mockFoo = mock(Foo.class, withSettings()
    .extraInterfaces(Bar.class, Baz.class)
    .name("fooMock"));

// Serializable mock
List<String> serializableMock = mock(List.class, withSettings()
    .serializable());

// Mock with constructor arguments
UserService userService = mock(UserService.class, withSettings()
    .useConstructor("database-url", 30));

// Lenient mock (bypasses strict stubbing)
List<String> lenientMock = mock(List.class, withSettings()
    .lenient());

Mock Introspection

MockingDetails Interface

Inspect mock objects and their configuration.

public static MockingDetails mockingDetails(Object toInspect)

interface MockingDetails {
    boolean isMock();
    boolean isSpy();
    Object getMock();
    Collection<Invocation> getInvocations();
    Collection<Stubbing> getStubbings();
    MockCreationSettings<?> getMockCreationSettings();
    MockHandler getMockHandler();
    String printInvocations();
}

Usage Examples:

List<String> mockList = mock(List.class);
MockingDetails details = mockingDetails(mockList);

if (details.isMock()) {
    System.out.println("Object is a mock");
}

if (details.isSpy()) {
    System.out.println("Object is a spy");
}

// Get the mock object itself
Object mockObject = details.getMock();

// Get invocation history
Collection<Invocation> invocations = details.getInvocations();

// Get stubbing information
Collection<Stubbing> stubbings = details.getStubbings();

// Get mock creation settings
MockCreationSettings<?> settings = details.getMockCreationSettings();
Class<?> mockedType = settings.getTypeToMock();
String mockName = settings.getName();

// Get mock handler (for advanced framework integration)
MockHandler handler = details.getMockHandler();

// Print detailed mock information for debugging
System.out.println(details.printInvocations());

Utility Methods

Resetting Mocks

Reset mock objects to their initial state.

public static void reset(Object... mocks)

Usage Example:

List<String> mockList = mock(List.class);
when(mockList.size()).thenReturn(10);

// Use mock...
mockList.size(); // returns 10

// Reset removes all stubbing and interaction history
reset(mockList);
mockList.size(); // returns 0 (default)

Clearing Invocations

Clear only invocation history while preserving stubbing.

public static <T> void clearInvocations(T... mocks)

Usage Example:

List<String> mockList = mock(List.class);
when(mockList.size()).thenReturn(10);

mockList.size(); // Invocation recorded
mockList.add("test"); // Another invocation

// Clear only invocations, keep stubbing
clearInvocations(mockList);

// Stubbing still works
assertEquals(10, mockList.size());

// But no previous invocations recorded for verification
verify(mockList, never()).add(anyString()); // Passes

Clearing All Caches

Clear Mockito's internal caches and state.

public static void clearAllCaches()

Usage Example:

// Clear all Mockito state (rarely needed)
clearAllCaches();

Framework Validation

Validate proper Mockito usage and detect potential issues.

public static void validateMockitoUsage()

Usage Example:

@Test
void testWithValidation() {
    // Test code with mocks...
    
    // Validate at end of test
    validateMockitoUsage();
}

Lenient Stubbing

Make individual stubbings bypass strict stubbing validation.

public static LenientStubber lenient()

Usage Example:

// Regular stubbing (subject to strict validation)
when(mock.someMethod()).thenReturn("value");

// Lenient stubbing (bypasses strict validation)
lenient().when(mock.someMethod()).thenReturn("value");

// Useful for stubbings that might not always be used
lenient().when(mock.optionalMethod()).thenReturn("fallback");

Framework Integration

Access Mockito's framework for advanced integrations.

public static MockitoFramework framework()

Usage Example:

MockitoFramework framework = framework();
InvocationFactory invocationFactory = framework.getInvocationFactory();

// Access framework plugins
MockMaker mockMaker = framework.getPlugins().getMockMaker();

Session Management

Manage mock sessions for better test isolation.

public static MockitoSessionBuilder mockitoSession()

Usage Example:

MockitoSession session = mockitoSession()
    .initMocks(this)
    .strictness(Strictness.STRICT_STUBS)
    .logger(new CustomLogger())
    .startMocking();

try {
    // Test code with session-managed mocks
    // ...
} finally {
    session.finishMocking();
}

Mock Types and Interfaces

MockCreationSettings Interface

Contains immutable mock creation configuration.

interface MockCreationSettings<T> {
    Class<T> getTypeToMock();
    Set<Class<?>> getExtraInterfaces();
    String getName();
    Object getSpiedInstance();
    Answer<Object> getDefaultAnswer();
    boolean isSerializable();
    SerializableMode getSerializableMode();
    List<InvocationListener> getInvocationListeners();
    List<VerificationStartedListener> getVerificationStartedListeners();
    boolean isStubOnly();
    Strictness getStrictness();
    boolean isLenient();
    String getMockMaker();
    Type getGenericTypeToMock();
    Object getOuterClassInstance();
    boolean isUsingConstructor();
    Object[] getConstructorArgs();
}

Enums and Constants

enum SerializableMode {
    NONE,
    BASIC,
    ACROSS_CLASSLOADERS
}

enum Strictness {
    LENIENT,
    WARN,
    STRICT_STUBS
}

// Default Answer implementations
Answer<Object> RETURNS_DEFAULTS
Answer<Object> RETURNS_SMART_NULLS
Answer<Object> RETURNS_MOCKS  
Answer<Object> RETURNS_DEEP_STUBS
Answer<Object> CALLS_REAL_METHODS
Answer<Object> RETURNS_SELF

Framework Integration Interfaces

For advanced framework integrators.

interface MockHandler {
    Object handle(Invocation invocation) throws Throwable;
    MockCreationSettings<?> getMockSettings();
    InvocationContainer getInvocationContainer();
}

interface InvocationContainer {
    // Marker interface for internal implementation
}

interface LenientStubber extends Stubber {
    // Extends Stubber with lenient behavior
}

Advanced Mock Configuration Examples

Comprehensive MockSettings Example

// Mock with all advanced settings
UserService mockUserService = mock(UserService.class, withSettings()
    .name("userServiceMock")
    .defaultAnswer(RETURNS_SMART_NULLS)
    .extraInterfaces(Auditable.class, Cacheable.class)
    .serializable(SerializableMode.ACROSS_CLASSLOADERS)
    .strictness(Strictness.LENIENT)
    .verboseLogging()
    .invocationListeners(new CustomInvocationListener())
    .verificationStartedListeners(new CustomVerificationListener())
    .stubbingLookupListeners(new CustomStubbingListener()));

// Cast to extra interfaces
Auditable auditableMock = (Auditable) mockUserService;
Cacheable cacheableMock = (Cacheable) mockUserService;

Constructor-based Mocking

// Mock abstract class with constructor arguments
AbstractService mockService = mock(AbstractService.class, withSettings()
    .useConstructor("database-url", 30, true)
    .defaultAnswer(CALLS_REAL_METHODS));

// Mock inner class with outer instance
OuterClass outer = new OuterClass();
OuterClass.InnerClass mockInner = mock(OuterClass.InnerClass.class, withSettings()
    .useConstructor()
    .outerInstance(outer)
    .defaultAnswer(CALLS_REAL_METHODS));

Generic Type Preservation

// Mock with generic type information
List<String> mockList = mock(List.class, withSettings()
    .genericTypeToMock(new TypeReference<List<String>>() {}.getType()));

Framework Integration Example

// Advanced framework integration
MockSettings advancedSettings = withSettings()
    .name("frameworkMock")
    .stubOnly() // Memory optimization
    .mockMaker("custom-mock-maker");

MockCreationSettings<UserService> settings = advancedSettings.build(UserService.class);
MockHandler handler = mockingDetails(mock).getMockHandler();

// Create invocation factory for programmatic invocations
InvocationFactory invocationFactory = framework().getInvocationFactory();

Install with Tessl CLI

npx tessl i tessl/maven-org-mockito--mockito-core

docs

additional-answers.md

additional-matchers.md

tessl/maven-org-mockito--mockito-core

mock-creation.md.css-3qkkll{font-size:var(--chakra-font-sizes-sm);font-weight:var(--chakra-font-weights-normal);color:var(--chakra-colors-gray-300);}docs/

Mock Creation and Configuration

Basic Mock Creation

Creating Mocks

Creating Spies

Mock Settings and Configuration

MockSettings Interface

Mock Introspection

MockingDetails Interface

Utility Methods

Resetting Mocks

Clearing Invocations

Clearing All Caches

Framework Validation

Lenient Stubbing

Framework Integration

Session Management

Mock Types and Interfaces

MockCreationSettings Interface

Enums and Constants

Framework Integration Interfaces

Advanced Mock Configuration Examples

Comprehensive MockSettings Example

Constructor-based Mocking

Generic Type Preservation

Framework Integration Example

mock-creation.mddocs/