public class Mockito extends ArgumentMatchers
This javadoc content is also available on the http://mockito.org web page. All documentation is kept in javadocs because it guarantees consistency between what's on the web and what's in the source code. It allows access to documentation straight from the IDE even if you work offline. It motivates Mockito developers to keep documentation up-to-date with the code that they write, every day, with every commit.
@Mock
annotation doReturn()
|doThrow()
|doAnswer()
|doNothing()
|doCallRealMethod()
family of methods@Captor
, @Spy
, @InjectMocks
(Since 1.8.3) @Spies
, @InjectMocks
and constructor injection goodness (Since 1.9.0)MockMaker
API (Since 1.9.5)MockitoSession
is usable by testing frameworks (Since 2.15.+)org.mockito.plugins.InstantiatorProvider
as it was leaking internal API. it was replaced by org.mockito.plugins.InstantiatorProvider2 (Since 2.15.4)
Mockito.lenient()
and MockSettings.lenient()
methods (Since 2.20.0)
repositories {
jcenter()
}
dependencies {
testCompile "org.mockito:mockito-core:+"
androidTestCompile "org.mockito:mockito-android:+"
}
You can continue to run the same unit tests on a regular VM by using the `mockito-core` artifact in your "testCompile" scope as shown
above. Be aware that you cannot use the inline mock maker on Android due to limitations in the Android VM.
If you encounter issues with mocking on Android, please open an issue
on the official issue tracker.
Do provide the version of Android you are working on and dependencies of your project.
repositories {
jcenter()
}
dependencies {
testCompile "org.mockito:mockito-inline:+"
}
Be aware that this artifact may be abolished when the inline mock making feature is integrated into the default mock maker.
For more information about inline mock making, see section 39.
add()
, get()
, clear()
methods).
//Let's import Mockito statically so that the code looks clearer
import static org.mockito.Mockito.*;
//mock creation
List mockedList = mock(List.class);
//using mock object
mockedList.add("one");
mockedList.clear();
//verification
verify(mockedList).add("one");
verify(mockedList).clear();
Once created, a mock will remember all interactions. Then you can selectively verify whatever interactions you are interested in.
//You can mock concrete classes, not just interfaces
LinkedList mockedList = mock(LinkedList.class);
//stubbing
when(mockedList.get(0)).thenReturn("first");
when(mockedList.get(1)).thenThrow(new RuntimeException());
//following prints "first"
System.out.println(mockedList.get(0));
//following throws runtime exception
System.out.println(mockedList.get(1));
//following prints "null" because get(999) was not stubbed
System.out.println(mockedList.get(999));
//Although it is possible to verify a stubbed invocation, usually it's just redundant
//If your code cares what get(0) returns, then something else breaks (often even before verify() gets executed).
//If your code doesn't care what get(0) returns, then it should not be stubbed.
verify(mockedList).get(0);
equals()
method.
Sometimes, when extra flexibility is required then you might use argument matchers:
//stubbing using built-in anyInt() argument matcher
when(mockedList.get(anyInt())).thenReturn("element");
//stubbing using custom matcher (let's say isValid() returns your own matcher implementation):
when(mockedList.contains(argThat(isValid()))).thenReturn(true);
//following prints "element"
System.out.println(mockedList.get(999));
//you can also verify using an argument matcher
verify(mockedList).get(anyInt());
//argument matchers can also be written as Java 8 Lambdas
verify(mockedList).add(argThat(someString -> someString.length() > 5));
Argument matchers allow flexible verification or stubbing.
Click here
or here
to see more built-in matchers
and examples of custom argument matchers / hamcrest matchers.
For information solely on custom argument matchers check out javadoc for ArgumentMatcher
class.
Be reasonable with using complicated argument matching.
The natural matching style using equals()
with occasional anyX()
matchers tend to give clean & simple tests.
Sometimes it's just better to refactor the code to allow equals()
matching or even implement equals()
method to help out with testing.
Also, read section 15 or javadoc for ArgumentCaptor
class.
ArgumentCaptor
is a special implementation of an argument matcher that captures argument values for further assertions.
Warning on argument matchers:
If you are using argument matchers, all arguments have to be provided by matchers.
The following example shows verification but the same applies to stubbing:
verify(mock).someMethod(anyInt(), anyString(), eq("third argument"));
//above is correct - eq() is also an argument matcher
verify(mock).someMethod(anyInt(), anyString(), "third argument");
//above is incorrect - exception will be thrown because third argument is given without an argument matcher.
Matcher methods like anyObject()
, eq()
do not return matchers.
Internally, they record a matcher on a stack and return a dummy value (usually null).
This implementation is due to static type safety imposed by the java compiler.
The consequence is that you cannot use anyObject()
, eq()
methods outside of verified/stubbed method.
//using mock
mockedList.add("once");
mockedList.add("twice");
mockedList.add("twice");
mockedList.add("three times");
mockedList.add("three times");
mockedList.add("three times");
//following two verifications work exactly the same - times(1) is used by default
verify(mockedList).add("once");
verify(mockedList, times(1)).add("once");
//exact number of invocations verification
verify(mockedList, times(2)).add("twice");
verify(mockedList, times(3)).add("three times");
//verification using never(). never() is an alias to times(0)
verify(mockedList, never()).add("never happened");
//verification using atLeast()/atMost()
verify(mockedList, atMostOnce()).add("once");
verify(mockedList, atLeastOnce()).add("three times");
verify(mockedList, atLeast(2)).add("three times");
verify(mockedList, atMost(5)).add("three times");
times(1) is the default. Therefore using times(1) explicitly can be omitted.
doThrow(new RuntimeException()).when(mockedList).clear();
//following throws RuntimeException:
mockedList.clear();
Read more about doThrow()
|doAnswer()
family of methods in section 12.
// A. Single mock whose methods must be invoked in a particular order
List singleMock = mock(List.class);
//using a single mock
singleMock.add("was added first");
singleMock.add("was added second");
//create an inOrder verifier for a single mock
InOrder inOrder = inOrder(singleMock);
//following will make sure that add is first called with "was added first", then with "was added second"
inOrder.verify(singleMock).add("was added first");
inOrder.verify(singleMock).add("was added second");
// B. Multiple mocks that must be used in a particular order
List firstMock = mock(List.class);
List secondMock = mock(List.class);
//using mocks
firstMock.add("was called first");
secondMock.add("was called second");
//create inOrder object passing any mocks that need to be verified in order
InOrder inOrder = inOrder(firstMock, secondMock);
//following will make sure that firstMock was called before secondMock
inOrder.verify(firstMock).add("was called first");
inOrder.verify(secondMock).add("was called second");
// Oh, and A + B can be mixed together at will
Verification in order is flexible - you don't have to verify all
interactions one-by-one but only those that you are interested in
testing in order.
Also, you can create an InOrder object passing only the mocks that are relevant for in-order verification.
//using mocks - only mockOne is interacted
mockOne.add("one");
//ordinary verification
verify(mockOne).add("one");
//verify that method was never called on a mock
verify(mockOne, never()).add("two");
//verify that other mocks were not interacted
verifyZeroInteractions(mockTwo, mockThree);
//using mocks
mockedList.add("one");
mockedList.add("two");
verify(mockedList).add("one");
//following verification will fail
verifyNoMoreInteractions(mockedList);
A word of warning:
Some users who did a lot of classic, expect-run-verify mocking tend to use verifyNoMoreInteractions()
very often, even in every test method.
verifyNoMoreInteractions()
is not recommended to use in every test method.
verifyNoMoreInteractions()
is a handy assertion from the interaction testing toolkit. Use it only when it's relevant.
Abusing it leads to overspecified, less maintainable tests.
See also never()
- it is more explicit and
communicates the intent well.
@Mock
annotation
public class ArticleManagerTest {
@Mock private ArticleCalculator calculator;
@Mock private ArticleDatabase database;
@Mock private UserProvider userProvider;
private ArticleManager manager;
@org.junit.jupiter.api.Test
void testSomethingInJunit5(@Mock ArticleDatabase database) {
Important! This needs to be somewhere in the base class or a test
runner:
MockitoAnnotations.openMocks(testClass);
You can use built-in runner: MockitoJUnitRunner
or a rule: MockitoRule
.
For JUnit5 tests, refer to the JUnit5 extension described in section 45.
Read more here: MockitoAnnotations
Iterable
or simply
collections. Those offer natural ways of stubbing (e.g. using real
collections). In rare scenarios stubbing consecutive calls could be useful,
though:
when(mock.someMethod("some arg"))
.thenThrow(new RuntimeException())
.thenReturn("foo");
//First call: throws runtime exception:
mock.someMethod("some arg");
//Second call: prints "foo"
System.out.println(mock.someMethod("some arg"));
//Any consecutive call: prints "foo" as well (last stubbing wins).
System.out.println(mock.someMethod("some arg"));
Alternative, shorter version of consecutive stubbing:
when(mock.someMethod("some arg"))
.thenReturn("one", "two", "three");
Warning : if instead of chaining .thenReturn()
calls, multiple stubbing with the same matchers or arguments
is used, then each stubbing will override the previous one:
//All mock.someMethod("some arg") calls will return "two"
when(mock.someMethod("some arg"))
.thenReturn("one")
when(mock.someMethod("some arg"))
.thenReturn("two")
Answer
interface.
Yet another controversial feature which was not included in Mockito
originally. We recommend simply stubbing with thenReturn()
or
thenThrow()
, which should be enough to test/test-drive
any clean & simple code. However, if you do have a need to stub with the generic Answer interface, here is an example:
when(mock.someMethod(anyString())).thenAnswer(
new Answer() {
public Object answer(InvocationOnMock invocation) {
Object[] args = invocation.getArguments();
Object mock = invocation.getMock();
return "called with arguments: " + Arrays.toString(args);
}
});
//Following prints "called with arguments: [foo]"
System.out.println(mock.someMethod("foo"));
doReturn()
|doThrow()
|
doAnswer()
|doNothing()
|doCallRealMethod()
family of methodswhen(Object)
because the compiler does not
like void methods inside brackets...
Use doThrow()
when you want to stub a void method with an exception:
doThrow(new RuntimeException()).when(mockedList).clear();
//following throws RuntimeException:
mockedList.clear();
You can use doThrow()
, doAnswer()
, doNothing()
, doReturn()
and doCallRealMethod()
in place of the corresponding call with when()
, for any method.
It is necessary when you
when()
, for all of your stubbing calls.
Read more about these methods:
Real spies should be used carefully and occasionally, for example when dealing with legacy code.
Spying on real objects can be associated with "partial mocking" concept. Before the release 1.8, Mockito spies were not real partial mocks. The reason was we thought partial mock is a code smell. At some point we found legitimate use cases for partial mocks (3rd party interfaces, interim refactoring of legacy code).
List list = new LinkedList();
List spy = spy(list);
//optionally, you can stub out some methods:
when(spy.size()).thenReturn(100);
//using the spy calls *real* methods
spy.add("one");
spy.add("two");
//prints "one" - the first element of a list
System.out.println(spy.get(0));
//size() method was stubbed - 100 is printed
System.out.println(spy.size());
//optionally, you can verify
verify(spy).add("one");
verify(spy).add("two");
when(Object)
for stubbing spies.
Therefore when using spies please consider doReturn
|Answer
|Throw()
family of
methods for stubbing. Example:
List list = new LinkedList();
List spy = spy(list);
//Impossible: real method is called so spy.get(0) throws IndexOutOfBoundsException (the list is yet empty)
when(spy.get(0)).thenReturn("foo");
//You have to use doReturn() for stubbing
doReturn("foo").when(spy).get(0);
It is the default answer so it will be used only when you don't stub the method call.
Foo mock = mock(Foo.class, Mockito.RETURNS_SMART_NULLS);
Foo mockTwo = mock(Foo.class, new YourOwnAnswer());
Read more about this interesting implementation of Answer: RETURNS_SMART_NULLS
equals()
method.
This is also the recommended way of matching arguments because it makes tests clean & simple.
In some situations though, it is helpful to assert on certain arguments after the actual verification.
For example:
ArgumentCaptor<Person> argument = ArgumentCaptor.forClass(Person.class);
verify(mock).doSomething(argument.capture());
assertEquals("John", argument.getValue().getName());
Warning: it is recommended to use ArgumentCaptor with verification but not with stubbing.
Using ArgumentCaptor with stubbing may decrease test readability because captor is created outside of assert (aka verify or 'then') block.
Also it may reduce defect localization because if stubbed method was not called then no argument is captured.
In a way ArgumentCaptor is related to custom argument matchers (see javadoc for ArgumentMatcher
class).
Both techniques can be used for making sure certain arguments were passed to mocks.
However, ArgumentCaptor may be a better fit if:
ArgumentMatcher
are usually better for stubbing.
Before release 1.8 spy()
was not producing real partial mocks and it was confusing for some users.
Read more about spying: here or in javadoc for spy(Object)
method.
//you can create partial mock with spy() method:
List list = spy(new LinkedList());
//you can enable partial mock capabilities selectively on mocks:
Foo mock = mock(Foo.class);
//Be sure the real implementation is 'safe'.
//If real implementation throws exceptions or depends on specific state of the object then you're in trouble.
when(mock.someMethod()).thenCallRealMethod();
As usual you are going to read the partial mock warning:
Object oriented programming is more less tackling complexity by dividing the complexity into separate, specific, SRPy objects.
How does partial mock fit into this paradigm? Well, it just doesn't...
Partial mock usually means that the complexity has been moved to a different method on the same object.
In most cases, this is not the way you want to design your application.
However, there are rare cases when partial mocks come handy: dealing with code you cannot change easily (3rd party interfaces, interim refactoring of legacy code etc.) However, I wouldn't use partial mocks for new, test-driven & well-designed code.
Instead of reset()
please consider writing simple, small and focused test methods over lengthy, over-specified tests.
First potential code smell is reset()
in the middle of the test method. This probably means you're testing too much.
Follow the whisper of your test methods: "Please keep us small & focused on single behavior".
There are several threads about it on mockito mailing list.
The only reason we added reset()
method is to
make it possible to work with container-injected mocks.
For more information see FAQ (here).
Don't harm yourself. reset()
in the middle of the test method is a code smell (you're probably testing too much).
List mock = mock(List.class);
when(mock.size()).thenReturn(10);
mock.add(1);
reset(mock);
//at this point the mock forgot any interactions & stubbing
In case of questions you may also post to mockito mailing list: http://groups.google.com/group/mockito
Next, you should know that Mockito validates if you use it correctly all the time.
However, there's a gotcha so please read the javadoc for validateMockitoUsage()
Start learning about BDD here: http://en.wikipedia.org/wiki/Behavior_Driven_Development
The problem is that current stubbing api with canonical role of when word does not integrate nicely with //given //when //then comments.
It's because stubbing belongs to given component of the test and not to the when component of the test.
Hence BDDMockito
class introduces an alias so that you stub method calls with BDDMockito.given(Object)
method.
Now it really nicely integrates with the given component of a BDD style test!
Here is how the test might look like:
import static org.mockito.BDDMockito.*;
Seller seller = mock(Seller.class);
Shop shop = new Shop(seller);
public void shouldBuyBread() throws Exception {
//given
given(seller.askForBread()).willReturn(new Bread());
//when
Goods goods = shop.buyBread();
//then
assertThat(goods, containBread());
}
WARNING: This should be rarely used in unit testing.
The behaviour was implemented for a specific use case of a BDD spec that had an unreliable external dependency. This was in a web environment and the objects from the external dependency were being serialized to pass between layers.
To create serializable mock use MockSettings.serializable()
:
List serializableMock = mock(List.class, withSettings().serializable());
The mock can be serialized assuming all the normal serialization requirements are met by the class.
Making a real object spy serializable is a bit more effort as the spy(...) method does not have an overloaded version which accepts MockSettings. No worries, you will hardly ever use it.
List<Object> list = new ArrayList<Object>();
List<Object> spy = mock(ArrayList.class, withSettings()
.spiedInstance(list)
.defaultAnswer(CALLS_REAL_METHODS)
.serializable());
@Captor
,
@Spy
,
@InjectMocks
(Since 1.8.3)Release 1.8.3 brings new annotations that may be helpful on occasion:
Captor
simplifies creation of ArgumentCaptor
- useful when the argument to capture is a nasty generic class and you want to avoid compiler warnings
Spy
- you can use it instead spy(Object)
.
InjectMocks
- injects mock or spy fields into tested object automatically.
Note that @InjectMocks
can also be used in combination with the @Spy
annotation, it means
that Mockito will inject mocks into the partial mock under test. This complexity is another good reason why you
should only use partial mocks as a last resort. See point 16 about partial mocks.
All new annotations are *only* processed on MockitoAnnotations.openMocks(Object)
.
Just like for @Mock
annotation you can use the built-in runner: MockitoJUnitRunner
or rule:
MockitoRule
.
Allows verifying with timeout. It causes a verify to wait for a specified period of time for a desired interaction rather than fails immediately if had not already happened. May be useful for testing in concurrent conditions.
This feature should be used rarely - figure out a better way of testing your multi-threaded system.
Not yet implemented to work with InOrder verification.
Examples:
//passes when someMethod() is called no later than within 100 ms
//exits immediately when verification is satisfied (e.g. may not wait full 100 ms)
verify(mock, timeout(100)).someMethod();
//above is an alias to:
verify(mock, timeout(100).times(1)).someMethod();
//passes as soon as someMethod() has been called 2 times under 100 ms
verify(mock, timeout(100).times(2)).someMethod();
//equivalent: this also passes as soon as someMethod() has been called 2 times under 100 ms
verify(mock, timeout(100).atLeast(2)).someMethod();
@Spies
,
@InjectMocks
and constructor injection goodness (Since 1.9.0)
Mockito will now try to instantiate @Spy
and will instantiate @InjectMocks
fields
using constructor injection, setter injection, or field injection.
To take advantage of this feature you need to use MockitoAnnotations.openMocks(Object)
, MockitoJUnitRunner
or MockitoRule
.
Read more about available tricks and the rules of injection in the javadoc for InjectMocks
//instead:
@Spy BeerDrinker drinker = new BeerDrinker();
//you can write:
@Spy BeerDrinker drinker;
//same applies to @InjectMocks annotation:
@InjectMocks LocalPub;
Mockito will now allow you to create mocks when stubbing. Basically, it allows to create a stub in one line of code. This can be helpful to keep test code clean. For example, some boring stub can be created & stubbed at field initialization in a test:
public class CarTest {
Car boringStubbedCar = when(mock(Car.class).shiftGear()).thenThrow(EngineNotStarted.class).getMock();
@Test public void should... {}
Mockito will now allow to ignore stubbing for the sake of verification.
Sometimes useful when coupled with verifyNoMoreInteractions()
or verification inOrder()
.
Helps avoiding redundant verification of stubbed calls - typically we're not interested in verifying stubs.
Warning, ignoreStubs()
might lead to overuse of verifyNoMoreInteractions(ignoreStubs(...));
Bear in mind that Mockito does not recommend bombarding every test with verifyNoMoreInteractions()
for the reasons outlined in javadoc for verifyNoMoreInteractions(Object...)
Some examples:
verify(mock).foo();
verify(mockTwo).bar();
//ignores all stubbed methods:
verifyNoMoreInteractions(ignoreStubs(mock, mockTwo));
//creates InOrder that will ignore stubbed
InOrder inOrder = inOrder(ignoreStubs(mock, mockTwo));
inOrder.verify(mock).foo();
inOrder.verify(mockTwo).bar();
inOrder.verifyNoMoreInteractions();
Advanced examples and more details can be found in javadoc for ignoreStubs(Object...)
Mockito offers API to inspect the details of a mock object. This API is useful for advanced users and mocking framework integrators.
//To identify whether a particular object is a mock or a spy:
Mockito.mockingDetails(someObject).isMock();
Mockito.mockingDetails(someObject).isSpy();
//Getting details like type to mock or default answer:
MockingDetails details = mockingDetails(mock);
details.getMockCreationSettings().getTypeToMock();
details.getMockCreationSettings().getDefaultAnswer();
//Getting invocations and stubbings of the mock:
MockingDetails details = mockingDetails(mock);
details.getInvocations();
details.getStubbings();
//Printing all interactions (including stubbing, unused stubs)
System.out.println(mockingDetails(mock).printInvocations());
For more information see javadoc for MockingDetails
.
Useful for spies or partial mocks of objects that are difficult to mock or spy using the usual spy API. Since Mockito 1.10.11, the delegate may or may not be of the same type as the mock. If the type is different, a matching method needs to be found on delegate type otherwise an exception is thrown. Possible use cases for this feature:
The difference with the regular spy:
spy(Object)
) contains all state from the spied instance
and the methods are invoked on the spy. The spied instance is only used at mock creation to copy the state from.
If you call a method on a regular spy and it internally calls other methods on this spy, those calls are remembered
for verifications, and they can be effectively stubbed.
See more information in docs for AdditionalAnswers.delegatesTo(Object)
.
MockMaker
API (Since 1.9.5)Driven by requirements and patches from Google Android guys Mockito now offers an extension point that allows replacing the proxy generation engine. By default, Mockito uses Byte Buddy to create dynamic proxies.
The extension point is for advanced users that want to extend Mockito. For example, it is now possible to use Mockito for Android testing with a help of dexmaker.
For more details, motivations and examples please refer to
the docs for MockMaker
.
given(dog.bark()).willReturn(2);
// when
...
then(person).should(times(2)).ride(bike);
For more information and an example see BDDMockito.then(Object)
spy(Object)
).
Previously, spying was only possible on instances of objects. New API makes it possible to use constructor when creating an instance of the mock. This is particularly useful for mocking abstract classes because the user is no longer required to provide an instance of the abstract class. At the moment, only parameter-less constructor is supported, let us know if it is not enough.
//convenience API, new overloaded spy() method:
SomeAbstract spy = spy(SomeAbstract.class);
//Mocking abstract methods, spying default methods of an interface (only available since 2.7.13)
Function function = spy(Function.class);
//Robust API, via settings builder:
OtherAbstract spy = mock(OtherAbstract.class, withSettings()
.useConstructor().defaultAnswer(CALLS_REAL_METHODS));
//Mocking an abstract class with constructor arguments (only available since 2.7.14)
SomeAbstract spy = mock(SomeAbstract.class, withSettings()
.useConstructor("arg1", 123).defaultAnswer(CALLS_REAL_METHODS));
//Mocking a non-static inner abstract class:
InnerAbstract spy = mock(InnerAbstract.class, withSettings()
.useConstructor().outerInstance(outerInstance).defaultAnswer(CALLS_REAL_METHODS));
For more information please see MockSettings.useConstructor(Object...)
.
// use regular serialization
mock(Book.class, withSettings().serializable());
// use serialization across classloaders
mock(Book.class, withSettings().serializable(ACROSS_CLASSLOADERS));
For more details see MockSettings.serializable(SerializableMode)
.
class Lines extends List<Line> {
// ...
}
lines = mock(Lines.class, RETURNS_DEEP_STUBS);
// Now Mockito understand this is not an Object but a Line
Line line = lines.iterator().next();
Please note that in most scenarios a mock returning a mock is wrong.
@Mock
, @Spy
, @InjectMocks
, etc.
@RunWith
(MockitoJUnitRunner
.class)
MockitoAnnotations.openMocks(Object)
in the @Before
method
@RunWith(YetAnotherRunner.class)
public class TheTest {
@Rule public MockitoRule mockito = MockitoJUnit.rule();
// ...
}
For more information see MockitoJUnit.rule()
.
PluginSwitch
.
Allows specifying a custom message to be printed if verification fails.
Examples:
// will print a custom message on verification failure
verify(mock, description("This will print on failure")).someMethod();
// will work with any verification mode
verify(mock, times(2).description("someMethod should be called twice")).someMethod();
You can use Java 8 lambda expressions with ArgumentMatcher
to reduce the dependency on ArgumentCaptor
.
If you need to verify that the input to a function call on a mock was correct, then you would normally
use the ArgumentCaptor
to find the operands used and then do subsequent assertions on them. While
for complex examples this can be useful, it's also long-winded.
Writing a lambda to express the match is quite easy. The argument to your function, when used in conjunction with argThat, will be passed to the ArgumentMatcher as a strongly typed object, so it is possible to do anything with it.
Examples:
// verify a list only had strings of a certain length added to it
// note - this will only compile under Java 8
verify(list, times(2)).add(argThat(string -> string.length() < 5));
// Java 7 equivalent - not as neat
verify(list, times(2)).add(argThat(new ArgumentMatcher(){
public boolean matches(String arg) {
return arg.length() < 5;
}
}));
// more complex Java 8 example - where you can specify complex verification behaviour functionally
verify(target, times(1)).receiveComplexObject(argThat(obj -> obj.getSubObject().get(0).equals("expected")));
// this can also be used when defining the behaviour of a mock under different inputs
// in this case if the input list was fewer than 3 items the mock returns null
when(mock.someMethod(argThat(list -> list.size()<3))).thenReturn(null);
As the Answer
interface has just one method it is already possible to implement it in Java 8 using
a lambda expression for very simple situations. The more you need to use the parameters of the method call,
the more you need to typecast the arguments from InvocationOnMock
.
Examples:
// answer by returning 12 every time
doAnswer(invocation -> 12).when(mock).doSomething();
// answer by using one of the parameters - converting into the right
// type as your go - in this case, returning the length of the second string parameter
// as the answer. This gets long-winded quickly, with casting of parameters.
doAnswer(invocation -> ((String)invocation.getArgument(1)).length())
.when(mock).doSomething(anyString(), anyString(), anyString());
For convenience it is possible to write custom answers/actions, which use the parameters to the method call,
as Java 8 lambdas. Even in Java 7 and lower these custom answers based on a typed interface can reduce boilerplate.
In particular, this approach will make it easier to test functions which use callbacks.
The methods answer
and answerVoid
can be used to create the answer. They rely on the related answer interfaces in org.mockito.stubbing
that
support answers up to 5 parameters.
Examples:
// Example interface to be mocked has a function like:
void execute(String operand, Callback callback);
// the example callback has a function and the class under test
// will depend on the callback being invoked
void receive(String item);
// Java 8 - style 1
doAnswer(AdditionalAnswers.answerVoid((operand, callback) -> callback.receive("dummy"))
.when(mock).execute(anyString(), any(Callback.class));
// Java 8 - style 2 - assuming static import of AdditionalAnswers
doAnswer(answerVoid((String operand, Callback callback) -> callback.receive("dummy"))
.when(mock).execute(anyString(), any(Callback.class));
// Java 8 - style 3 - where mocking function to is a static member of test class
private static void dummyCallbackImpl(String operation, Callback callback) {
callback.receive("dummy");
}
doAnswer(answerVoid(TestClass::dummyCallbackImpl)
.when(mock).execute(anyString(), any(Callback.class));
// Java 7
doAnswer(answerVoid(new VoidAnswer2() {
public void answer(String operation, Callback callback) {
callback.receive("dummy");
}})).when(mock).execute(anyString(), any(Callback.class));
// returning a value is possible with the answer() function
// and the non-void version of the functional interfaces
// so if the mock interface had a method like
boolean isSameString(String input1, String input2);
// this could be mocked
// Java 8
doAnswer(AdditionalAnswers.answer((input1, input2) -> input1.equals(input2))))
.when(mock).execute(anyString(), anyString());
// Java 7
doAnswer(answer(new Answer2() {
public String answer(String input1, String input2) {
return input1 + input2;
}})).when(mock).execute(anyString(), anyString());
Mockito now preserves annotations on mocked methods and types as well as generic meta data. Previously, a mock type did not preserve annotations on types unless they were explicitly inherited and never retained annotations on methods. As a consequence, the following conditions now hold true:
@MyAnnotation
class Foo {
List<String> bar() { ... }
}
Class<?> mockType = mock(Foo.class).getClass();
assert mockType.isAnnotationPresent(MyAnnotation.class);
assert mockType.getDeclaredMethod("bar").getGenericReturnType() instanceof ParameterizedType;
When using Java 8, Mockito now also preserves type annotations. This is default behavior and might not hold if an
alternative MockMaker
is used.
Incubating
, optional support for mocking final classes and methods.
This is a fantastic improvement that demonstrates Mockito's everlasting quest for improving testing experience.
Our ambition is that Mockito "just works" with final classes and methods.
Previously they were considered unmockable, preventing the user from mocking.
We already started discussing how to make this feature enabled by default.
Currently, the feature is still optional as we wait for more feedback from the community.
This alternative mock maker which uses a combination of both Java instrumentation API and sub-classing rather than creating a new class to represent a mock. This way, it becomes possible to mock final types and methods.
This mock maker is turned off by default because it is based on completely different mocking mechanism
that requires more feedback from the community. It can be activated explicitly by the mockito extension mechanism,
just create in the classpath a file /mockito-extensions/org.mockito.plugins.MockMaker
containing the value mock-maker-inline
.
As a convenience, the Mockito team provides an artifact where this mock maker is preconfigured. Instead of using the mockito-core artifact, include the mockito-inline artifact in your project. Note that this artifact is likely to be discontinued once mocking of final classes and methods gets integrated into the default mock maker.
Some noteworthy notes about this mock maker:
withSettings().serializable()
withSettings().extraInterfaces()
java.*
native
methods-javaagent
parameter upon starting the JVM.
If you are interested in more details of this feature please read the javadoc of
org.mockito.internal.creation.bytebuddy.InlineByteBuddyMockMaker
MockitoRule.strictness(Strictness)
with Strictness.STRICT_STUBS
MockitoJUnitRunner.StrictStubs
MockitoSession
MockitoJUnitRunner
MockitoHint
Being "loose" by default makes Mockito tests harder to debug at times. There are scenarios where misconfigured stubbing (like using a wrong argument) forces the user to run the test with a debugger. Ideally, tests failures are immediately obvious and don't require debugger to identify the root cause. Starting with version 2.1 Mockito has been getting new features that nudge the framework towards "strictness". We want Mockito to offer fantastic debuggability while not losing its core mocking style, optimized for intuitiveness, explicitness and clean test code.
Help Mockito! Try the new features, give us feedback, join the discussion about Mockito strictness at GitHub issue 769.
MockitoPlugins
-
Enables framework integrators to get access to default Mockito plugins.
Useful when one needs to implement custom plugin such as MockMaker
and delegate some behavior to the default Mockito implementation.
MockSettings.build(Class)
-
Creates immutable view of mock settings used later by Mockito.
Useful for creating invocations with InvocationFactory
or when implementing custom MockHandler
.
MockingDetails.getMockHandler()
-
Other frameworks may use the mock handler to programmatically simulate invocations on mock objects.
MockHandler.getMockSettings()
-
Useful to get hold of the setting the mock object was created with.
InvocationFactory
-
Provides means to create instances of Invocation
objects.
Useful for framework integrations that need to programmatically simulate method calls on mock objects.
MockHandler.getInvocationContainer()
-
Provides access to invocation container object which has no methods (marker interface).
Container is needed to hide the internal implementation and avoid leaking it to the public API.
Stubbing
-
it now extends Answer
interface.
It is backwards compatible because Stubbing interface is not extensible (see NotExtensible
).
The change should be seamless to our users.
InternalMockHandler
-
In order to accommodate API changes we needed to deprecate this interface.
The interface was always documented as internal, we don't have evidence it was used by the community.
The deprecation should be completely seamless for our users.
NotExtensible
-
Public annotation that indicates to the user that she should not provide custom implementations of given type.
Helps framework integrators and our users understand how to use Mockito API safely.
VerificationStartedListener
and VerificationStartedEvent
enable framework integrators to replace the mock object for verification.
The main driving use case is Spring Boot integration.
For details see Javadoc for VerificationStartedListener
.
MockSettings.verificationStartedListeners(VerificationStartedListener...)
allows to supply verification started listeners at mock creation time.
MockingDetails.getMock()
was added to make the MockingDetails
API more complete.
We found this method useful during the implementation.
MockitoSession
is usable by testing frameworks (Since 2.15.+)MockitoSessionBuilder
and MockitoSession
were enhanced to enable reuse by testing framework
integrations (e.g. MockitoRule
for JUnit):
MockitoSessionBuilder.initMocks(Object...)
allows to pass in multiple test class instances for
initialization of fields annotated with Mockito annotations like Mock
.
This method is useful for advanced framework integrations (e.g. JUnit Jupiter), when a test uses multiple,
e.g. nested, test class instances.
MockitoSessionBuilder.name(String)
allows to pass a name from the testing framework to the
MockitoSession
that will be used for printing warnings when Strictness.WARN
is used.
MockitoSessionBuilder.logger(MockitoSessionLogger)
makes it possible to customize the logger used
for hints/warnings produced when finishing mocking (useful for testing and to connect reporting capabilities
provided by testing frameworks such as JUnit Jupiter).
MockitoSession.setStrictness(Strictness)
allows to change the strictness of a MockitoSession
for one-off scenarios, e.g. it enables configuring a default strictness for all tests in a class but makes it
possible to change the strictness for a single or a few tests.
MockitoSession.finishMocking(Throwable)
was added to avoid confusion that may arise because
there are multiple competing failures. It will disable certain checks when the supplied failure
is not null
.
org.mockito.plugins.InstantiatorProvider
as it was leaking internal API. it was
replaced by org.mockito.plugins.InstantiatorProvider2 (Since 2.15.4)
InstantiatorProvider
returned an internal API. Hence it was deprecated and replaced
by InstantiatorProvider2
. Old instantiator providers
will continue to work, but it is recommended to switch to the new API.
MockitoExtension
.
Mockito.lenient()
and MockSettings.lenient()
methods (Since 2.20.0)Strictness.STRICT_STUBS
).
This comes with a trade-off: in some cases, you may get false negatives from strict stubbing.
To remedy those scenarios you can now configure specific stubbing to be lenient, while all the other stubbings and mocks use strict stubbing:
lenient().when(mock.foo()).thenReturn("ok");
If you want all the stubbings on a given mock to be lenient, you can configure the mock accordingly:
Foo mock = Mockito.mock(Foo.class, withSettings().lenient());
For more information refer to lenient()
.
Let us know how do you find the new feature by opening a GitHub issue to discuss!
MockitoFramework.clearInlineMocks()
.
If you have feedback or a better idea how to solve the problem please reach out.
Foo
type's static method would return foo
unless mocked:
assertEquals("foo", Foo.method());
try (MockedStatic mocked = mockStatic(Foo.class)) {
mocked.when(Foo::method).thenReturn("bar");
assertEquals("bar", Foo.method());
mocked.verify(Foo::method);
}
assertEquals("foo", Foo.method());
Due to the defined scope of the static mock, it returns to its original behvior once the scope is released. To define mock
behavior and to verify static method invocations, use the MockedStatic
that is returned.
Modifier and Type | Field and Description |
---|---|
static Answer<Object> |
CALLS_REAL_METHODS
Optional
Answer to be used with mock(Class, Answer) |
static Answer<Object> |
RETURNS_DEEP_STUBS
Optional
Answer to be used with mock(Class, Answer) . |
static Answer<Object> |
RETURNS_DEFAULTS
The default
Answer of every mock if the mock was not stubbed. |
static Answer<Object> |
RETURNS_MOCKS
Optional
Answer to be used with mock(Class, Answer) |
static Answer<Object> |
RETURNS_SELF
Optional
Answer to be used with mock(Class, Answer) . |
static Answer<Object> |
RETURNS_SMART_NULLS
Optional
Answer to be used with mock(Class, Answer) . |
Constructor and Description |
---|
Mockito() |
Modifier and Type | Method and Description |
---|---|
static VerificationAfterDelay |
after(long millis)
Verification will be triggered after given amount of millis, allowing testing of async code.
|
static VerificationMode |
atLeast(int minNumberOfInvocations)
Allows at-least-x verification.
|
static VerificationMode |
atLeastOnce()
Allows at-least-once verification.
|
static VerificationMode |
atMost(int maxNumberOfInvocations)
Allows at-most-x verification.
|
static VerificationMode |
atMostOnce()
Allows at-most-once verification.
|
static VerificationMode |
calls(int wantedNumberOfInvocations)
Allows non-greedy verification in order.
|
static <T> void |
clearInvocations(T... mocks)
Use this method in order to only clear invocations, when stubbing is non-trivial.
|
static VerificationMode |
description(String description)
Adds a description to be printed if verification fails.
|
static Stubber |
doAnswer(Answer answer)
Use
doAnswer() when you want to stub a void method with generic Answer . |
static Stubber |
doCallRealMethod()
Use
doCallRealMethod() when you want to call the real implementation of a method. |
static Stubber |
doNothing()
Use
doNothing() for setting void methods to do nothing. |
static Stubber |
doReturn(Object toBeReturned)
Use
doReturn() in those rare occasions when you cannot use when(Object) . |
static Stubber |
doReturn(Object toBeReturned,
Object... toBeReturnedNext)
Same as
doReturn(Object) but sets consecutive values to be returned. |
static Stubber |
doThrow(Class<? extends Throwable> toBeThrown)
Use
doThrow() when you want to stub the void method with an exception. |
static Stubber |
doThrow(Class<? extends Throwable> toBeThrown,
Class<? extends Throwable>... toBeThrownNext)
Same as
doThrow(Class) but sets consecutive exception classes to be thrown. |
static Stubber |
doThrow(Throwable... toBeThrown)
Use
doThrow() when you want to stub the void method with an exception. |
static MockitoFramework |
framework()
For advanced users or framework integrators.
|
static Object[] |
ignoreStubs(Object... mocks)
Ignores stubbed methods of given mocks for the sake of verification.
|
static InOrder |
inOrder(Object... mocks)
Creates
InOrder object that allows verifying mocks in order. |
static LenientStubber |
lenient()
Lenient stubs bypass "strict stubbing" validation (see
Strictness.STRICT_STUBS ). |
static <T> T |
mock(Class<T> classToMock)
Creates mock object of given class or interface.
|
static <T> T |
mock(Class<T> classToMock,
Answer defaultAnswer)
Creates mock with a specified strategy for its answers to interactions.
|
static <T> T |
mock(Class<T> classToMock,
MockSettings mockSettings)
Creates a mock with some non-standard settings.
|
static <T> T |
mock(Class<T> classToMock,
String name)
Specifies mock name.
|
static MockingDetails |
mockingDetails(Object toInspect)
Returns a MockingDetails instance that enables inspecting a particular object for Mockito related information.
|
static MockitoSessionBuilder |
mockitoSession()
MockitoSession is an optional, highly recommended feature
that helps driving cleaner tests by eliminating boilerplate code and adding extra validation. |
static <T> MockedStatic<T> |
mockStatic(Class<T> classToMock)
Creates a thread-local mock controller for all static methods of the given class or interface.
|
static <T> MockedStatic<T> |
mockStatic(Class<T> classToMock,
Answer defaultAnswer)
Creates a thread-local mock controller for all static methods of the given class or interface.
|
static <T> MockedStatic<T> |
mockStatic(Class<T> classToMock,
MockSettings mockSettings)
Creates a thread-local mock controller for all static methods of the given class or interface.
|
static <T> MockedStatic<T> |
mockStatic(Class<T> classToMock,
String name)
Creates a thread-local mock controller for all static methods of the given class or interface.
|
static VerificationMode |
never()
Alias to
times(0) , see times(int) |
static VerificationMode |
only()
Allows checking if given method was the only one invoked.
|
static <T> void |
reset(T... mocks)
Smart Mockito users hardly use this feature because they know it could be a sign of poor tests.
|
static <T> T |
spy(Class<T> classToSpy)
Please refer to the documentation of
spy(Object) . |
static <T> T |
spy(T object)
Creates a spy of the real object.
|
static VerificationWithTimeout |
timeout(long millis)
Verification will be triggered over and over until the given amount of millis, allowing testing of async code.
|
static VerificationMode |
times(int wantedNumberOfInvocations)
Allows verifying exact number of invocations.
|
static void |
validateMockitoUsage()
First of all, in case of any trouble, I encourage you to read the Mockito FAQ: https://github.com/mockito/mockito/wiki/FAQ
|
static <T> T |
verify(T mock)
Verifies certain behavior happened once.
|
static <T> T |
verify(T mock,
VerificationMode mode)
Verifies certain behavior happened at least once / exact number of times / never.
|
static void |
verifyNoInteractions(Object... mocks)
Verifies that no interactions happened on given mocks.
|
static void |
verifyNoMoreInteractions(Object... mocks)
Checks if any of given mocks has any unverified interaction.
|
static void |
verifyZeroInteractions(Object... mocks)
Deprecated.
Since 3.0.1. Please migrate your code to
verifyNoInteractions(Object...) |
static <T> OngoingStubbing<T> |
when(T methodCall)
Enables stubbing methods.
|
static MockSettings |
withSettings()
Allows mock creation with additional mock settings.
|
any, any, anyBoolean, anyByte, anyChar, anyCollection, anyCollectionOf, anyDouble, anyFloat, anyInt, anyIterable, anyIterableOf, anyList, anyListOf, anyLong, anyMap, anyMapOf, anyObject, anySet, anySetOf, anyShort, anyString, anyVararg, argThat, booleanThat, byteThat, charThat, contains, doubleThat, endsWith, eq, eq, eq, eq, eq, eq, eq, eq, eq, floatThat, intThat, isA, isNotNull, isNotNull, isNull, isNull, longThat, matches, matches, notNull, notNull, nullable, refEq, same, shortThat, startsWith
public static final Answer<Object> RETURNS_DEFAULTS
Answer
of every mock if the mock was not stubbed.
Typically it just returns some empty value.
Answer
can be used to define the return values of unstubbed invocations.
This implementation first tries the global configuration and if there is no global configuration then it will use a default answer that returns zeros, empty collections, nulls, etc.
public static final Answer<Object> RETURNS_SMART_NULLS
Answer
to be used with mock(Class, Answer)
.
Answer
can be used to define the return values of unstubbed invocations.
This implementation can be helpful when working with legacy code.
Unstubbed methods often return null. If your code uses the object returned by an unstubbed call you get a NullPointerException.
This implementation of Answer returns SmartNull instead of null.
SmartNull
gives nicer exception message than NPE because it points out the line where unstubbed method was called. You just click on the stack trace.
ReturnsSmartNulls
first tries to return ordinary values (zeros, empty collections, empty string, etc.)
then it tries to return SmartNull. If the return type is final then plain null
is returned.
ReturnsSmartNulls
will be probably the default return values strategy in Mockito 4.0.0
Example:
Foo mock = mock(Foo.class, RETURNS_SMART_NULLS);
//calling unstubbed method here:
Stuff stuff = mock.getStuff();
//using object returned by unstubbed call:
stuff.doSomething();
//Above doesn't yield NullPointerException this time!
//Instead, SmartNullPointerException is thrown.
//Exception's cause links to unstubbed mock.getStuff() - just click on the stack trace.
public static final Answer<Object> RETURNS_MOCKS
Answer
to be used with mock(Class, Answer)
Answer
can be used to define the return values of unstubbed invocations.
This implementation can be helpful when working with legacy code.
ReturnsMocks first tries to return ordinary values (zeros, empty collections, empty string, etc.)
then it tries to return mocks. If the return type cannot be mocked (e.g. is final) then plain null
is returned.
public static final Answer<Object> RETURNS_DEEP_STUBS
Answer
to be used with mock(Class, Answer)
.
Example that shows how deep stub works:
Foo mock = mock(Foo.class, RETURNS_DEEP_STUBS);
// note that we're stubbing a chain of methods here: getBar().getName()
when(mock.getBar().getName()).thenReturn("deep");
// note that we're chaining method calls: getBar().getName()
assertEquals("deep", mock.getBar().getName());
WARNING: This feature should rarely be required for regular clean code! Leave it for legacy code. Mocking a mock to return a mock, to return a mock, (...), to return something meaningful hints at violation of Law of Demeter or mocking a value object (a well known anti-pattern).
Good quote I've seen one day on the web: every time a mock returns a mock a fairy dies.
Please note that this answer will return existing mocks that matches the stub. This behavior is ok with deep stubs and allows verification to work on the last mock of the chain.
when(mock.getBar(anyString()).getThingy().getName()).thenReturn("deep");
mock.getBar("candy bar").getThingy().getName();
assertSame(mock.getBar(anyString()).getThingy().getName(), mock.getBar(anyString()).getThingy().getName());
verify(mock.getBar("candy bar").getThingy()).getName();
verify(mock.getBar(anyString()).getThingy()).getName();
Verification only works with the last mock in the chain. You can use verification modes.
when(person.getAddress(anyString()).getStreet().getName()).thenReturn("deep");
when(person.getAddress(anyString()).getStreet(Locale.ITALIAN).getName()).thenReturn("deep");
when(person.getAddress(anyString()).getStreet(Locale.CHINESE).getName()).thenReturn("deep");
person.getAddress("the docks").getStreet().getName();
person.getAddress("the docks").getStreet().getLongName();
person.getAddress("the docks").getStreet(Locale.ITALIAN).getName();
person.getAddress("the docks").getStreet(Locale.CHINESE).getName();
// note that we are actually referring to the very last mock in the stubbing chain.
InOrder inOrder = inOrder(
person.getAddress("the docks").getStreet(),
person.getAddress("the docks").getStreet(Locale.CHINESE),
person.getAddress("the docks").getStreet(Locale.ITALIAN)
);
inOrder.verify(person.getAddress("the docks").getStreet(), times(1)).getName();
inOrder.verify(person.getAddress("the docks").getStreet()).getLongName();
inOrder.verify(person.getAddress("the docks").getStreet(Locale.ITALIAN), atLeast(1)).getName();
inOrder.verify(person.getAddress("the docks").getStreet(Locale.CHINESE)).getName();
How deep stub work internally?
//this:
Foo mock = mock(Foo.class, RETURNS_DEEP_STUBS);
when(mock.getBar().getName(), "deep");
//is equivalent of
Foo foo = mock(Foo.class);
Bar bar = mock(Bar.class);
when(foo.getBar()).thenReturn(bar);
when(bar.getName()).thenReturn("deep");
This feature will not work when any return type of methods included in the chain cannot be mocked (for example: is a primitive or a final class). This is because of java type system.
public static final Answer<Object> CALLS_REAL_METHODS
Answer
to be used with mock(Class, Answer)
Answer
can be used to define the return values of unstubbed invocations.
This implementation can be helpful when working with legacy code. When this implementation is used, unstubbed methods will delegate to the real implementation. This is a way to create a partial mock object that calls real methods by default.
As usual you are going to read the partial mock warning: Object oriented programming is more less tackling complexity by dividing the complexity into separate, specific, SRPy objects. How does partial mock fit into this paradigm? Well, it just doesn't... Partial mock usually means that the complexity has been moved to a different method on the same object. In most cases, this is not the way you want to design your application.
However, there are rare cases when partial mocks come handy: dealing with code you cannot change easily (3rd party interfaces, interim refactoring of legacy code etc.) However, I wouldn't use partial mocks for new, test-driven & well-designed code.
Example:
Foo mock = mock(Foo.class, CALLS_REAL_METHODS);
// this calls the real implementation of Foo.getSomething()
value = mock.getSomething();
doReturn(fakeValue).when(mock).getSomething();
// now fakeValue is returned
value = mock.getSomething();
Note 1: Stubbing partial mocks using when(mock.getSomething()).thenReturn(fakeValue)
syntax will call the real method. For partial mock it's recommended to use doReturn
syntax.
Note 2: If the mock is serialized then deserialized, then this answer will not be able to understand generics metadata.
public static final Answer<Object> RETURNS_SELF
Answer
to be used with mock(Class, Answer)
.
Allows Builder mocks to return itself whenever a method is invoked that returns a Type equal
to the class or a superclass.
Keep in mind this answer uses the return type of a method.
If this type is assignable to the class of the mock, it will return the mock.
Therefore if you have a method returning a superclass (for example Object
) it will match and return the mock.
public class HttpRequesterWithHeaders {
private HttpBuilder builder;
public HttpRequesterWithHeaders(HttpBuilder builder) {
this.builder = builder;
}
public String request(String uri) {
return builder.withUrl(uri)
.withHeader("Content-type: application/json")
.withHeader("Authorization: Bearer")
.request();
}
}
private static class HttpBuilder {
private String uri;
private List<String> headers;
public HttpBuilder() {
this.headers = new ArrayList<String>();
}
public HttpBuilder withUrl(String uri) {
this.uri = uri;
return this;
}
public HttpBuilder withHeader(String header) {
this.headers.add(header);
return this;
}
public String request() {
return uri + headers.toString();
}
}
The following test will succeed
@Test
public void use_full_builder_with_terminating_method() {
HttpBuilder builder = mock(HttpBuilder.class, RETURNS_SELF);
HttpRequesterWithHeaders requester = new HttpRequesterWithHeaders(builder);
String response = "StatusCode: 200";
when(builder.request()).thenReturn(response);
assertThat(requester.request("URI")).isEqualTo(response);
}
public static <T> T mock(Class<T> classToMock)
See examples in javadoc for Mockito
class
classToMock
- class or interface to mockpublic static <T> T mock(Class<T> classToMock, String name)
Beware that naming mocks is not a solution for complex code which uses too many mocks or collaborators. If you have too many mocks then refactor the code so that it's easy to test/debug without necessity of naming mocks.
If you use @Mock
annotation then you've got naming mocks for free! @Mock
uses field name as mock name. Read more.
See examples in javadoc for Mockito
class
classToMock
- class or interface to mockname
- of the mockpublic static MockingDetails mockingDetails(Object toInspect)
In future Mockito versions MockingDetails may grow and provide other useful information about the mock, e.g. invocations, stubbing info, etc.
toInspect
- - object to inspect. null input is allowed.MockingDetails
instance.public static <T> T mock(Class<T> classToMock, Answer defaultAnswer)
It is the default answer so it will be used only when you don't stub the method call.
Foo mock = mock(Foo.class, RETURNS_SMART_NULLS);
Foo mockTwo = mock(Foo.class, new YourOwnAnswer());
See examples in javadoc for Mockito
class
classToMock
- class or interface to mockdefaultAnswer
- default answer for unstubbed methodspublic static <T> T mock(Class<T> classToMock, MockSettings mockSettings)
The number of configuration points for a mock grows
so we need a fluent way to introduce new configuration without adding more and more overloaded Mockito.mock() methods.
Hence MockSettings
.
Listener mock = mock(Listener.class, withSettings()
.name("firstListner").defaultBehavior(RETURNS_SMART_NULLS));
);
Use it carefully and occasionally. What might be reason your test needs non-standard mocks?
Is the code under test so complicated that it requires non-standard mocks?
Wouldn't you prefer to refactor the code under test so it is testable in a simple way?
See also withSettings()
See examples in javadoc for Mockito
class
classToMock
- class or interface to mockmockSettings
- additional mock settingspublic static <T> T spy(T object)
Real spies should be used carefully and occasionally, for example when dealing with legacy code.
As usual you are going to read the partial mock warning: Object oriented programming tackles complexity by dividing the complexity into separate, specific, SRPy objects. How does partial mock fit into this paradigm? Well, it just doesn't... Partial mock usually means that the complexity has been moved to a different method on the same object. In most cases, this is not the way you want to design your application.
However, there are rare cases when partial mocks come handy: dealing with code you cannot change easily (3rd party interfaces, interim refactoring of legacy code etc.) However, I wouldn't use partial mocks for new, test-driven & well-designed code.
Example:
List list = new LinkedList();
List spy = spy(list);
//optionally, you can stub out some methods:
when(spy.size()).thenReturn(100);
//using the spy calls real methods
spy.add("one");
spy.add("two");
//prints "one" - the first element of a list
System.out.println(spy.get(0));
//size() method was stubbed - 100 is printed
System.out.println(spy.size());
//optionally, you can verify
verify(spy).add("one");
verify(spy).add("two");
when(Object)
for stubbing spies.
Therefore for spies it is recommended to always use doReturn
|Answer
|Throw()
|CallRealMethod
family of methods for stubbing. Example:
List list = new LinkedList();
List spy = spy(list);
//Impossible: real method is called so spy.get(0) throws IndexOutOfBoundsException (the list is yet empty)
when(spy.get(0)).thenReturn("foo");
//You have to use doReturn() for stubbing
doReturn("foo").when(spy).get(0);
See examples in javadoc for Mockito
class
Note that the spy won't have any annotations of the spied type, because CGLIB won't rewrite them. It may troublesome for code that rely on the spy to have these annotations.
object
- to spy on@Incubating public static <T> T spy(Class<T> classToSpy)
spy(Object)
.
Overusing spies hints at code design smells.
This method, in contrast to the original spy(Object)
, creates a spy based on class instead of an object.
Sometimes it is more convenient to create spy based on the class and avoid providing an instance of a spied object.
This is particularly useful for spying on abstract classes because they cannot be instantiated.
See also MockSettings.useConstructor(Object...)
.
Examples:
SomeAbstract spy = spy(SomeAbstract.class);
//Robust API, via settings builder:
OtherAbstract spy = mock(OtherAbstract.class, withSettings()
.useConstructor().defaultAnswer(CALLS_REAL_METHODS));
//Mocking a non-static inner abstract class:
InnerAbstract spy = mock(InnerAbstract.class, withSettings()
.useConstructor().outerInstance(outerInstance).defaultAnswer(CALLS_REAL_METHODS));
T
- type of the spyclassToSpy
- the class to spy@Incubating public static <T> MockedStatic<T> mockStatic(Class<T> classToMock)
MockedStatic.close()
method must be called upon completing the
test or the mock will remain active on the current thread.
Note: We recommend against mocking static methods of classes in the standard library or classes used by custom class loaders used to executed the block with the mocked class. A mock maker might forbid mocking static methods of know classes that are known to cause problems. Also, if a static method is a JVM-intrinsic, it cannot typically be mocked even if not explicitly forbidden.
See examples in javadoc for Mockito
class
classToMock
- class or interface of which static mocks should be mocked.@Incubating public static <T> MockedStatic<T> mockStatic(Class<T> classToMock, Answer defaultAnswer)
MockedStatic.close()
method must be called upon completing the
test or the mock will remain active on the current thread.
Note: We recommend against mocking static methods of classes in the standard library or classes used by custom class loaders used to executed the block with the mocked class. A mock maker might forbid mocking static methods of know classes that are known to cause problems. Also, if a static method is a JVM-intrinsic, it cannot typically be mocked even if not explicitly forbidden.
See examples in javadoc for Mockito
class
classToMock
- class or interface of which static mocks should be mocked.defaultAnswer
- the default answer when invoking static methods.@Incubating public static <T> MockedStatic<T> mockStatic(Class<T> classToMock, String name)
MockedStatic.close()
method must be called upon completing the
test or the mock will remain active on the current thread.
Note: We recommend against mocking static methods of classes in the standard library or classes used by custom class loaders used to executed the block with the mocked class. A mock maker might forbid mocking static methods of know classes that are known to cause problems. Also, if a static method is a JVM-intrinsic, it cannot typically be mocked even if not explicitly forbidden.
See examples in javadoc for Mockito
class
classToMock
- class or interface of which static mocks should be mocked.name
- the name of the mock to use in error messages.@Incubating public static <T> MockedStatic<T> mockStatic(Class<T> classToMock, MockSettings mockSettings)
MockedStatic.close()
method must be called upon completing the
test or the mock will remain active on the current thread.
Note: We recommend against mocking static methods of classes in the standard library or classes used by custom class loaders used to executed the block with the mocked class. A mock maker might forbid mocking static methods of know classes that are known to cause problems. Also, if a static method is a JVM-intrinsic, it cannot typically be mocked even if not explicitly forbidden.
See examples in javadoc for Mockito
class
classToMock
- class or interface of which static mocks should be mocked.mockSettings
- the settings to use where only name and default answer are considered.public static <T> OngoingStubbing<T> when(T methodCall)
Simply put: "When the x method is called then return y".
Examples:
when(mock.someMethod()).thenReturn(10);
//you can use flexible argument matchers, e.g:
when(mock.someMethod(anyString())).thenReturn(10);
//setting exception to be thrown:
when(mock.someMethod("some arg")).thenThrow(new RuntimeException());
//you can set different behavior for consecutive method calls.
//Last stubbing (e.g: thenReturn("foo")) determines the behavior of further consecutive calls.
when(mock.someMethod("some arg"))
.thenThrow(new RuntimeException())
.thenReturn("foo");
//Alternative, shorter version for consecutive stubbing:
when(mock.someMethod("some arg"))
.thenReturn("one", "two");
//is the same as:
when(mock.someMethod("some arg"))
.thenReturn("one")
.thenReturn("two");
//shorter version for consecutive method calls throwing exceptions:
when(mock.someMethod("some arg"))
.thenThrow(new RuntimeException(), new NullPointerException();
For stubbing void methods with throwables see: doThrow(Throwable...)
Stubbing can be overridden: for example common stubbing can go to fixture setup but the test methods can override it. Please note that overridding stubbing is a potential code smell that points out too much stubbing.
Once stubbed, the method will always return stubbed value regardless of how many times it is called.
Last stubbing is more important - when you stubbed the same method with the same arguments many times.
Although it is possible to verify a stubbed invocation, usually it's just redundant.
Let's say you've stubbed foo.bar()
.
If your code cares what foo.bar()
returns then something else breaks(often before even verify()
gets executed).
If your code doesn't care what get(0)
returns then it should not be stubbed.
See examples in javadoc for Mockito
class
methodCall
- method to be stubbedpublic static <T> T verify(T mock)
Alias to verify(mock, times(1))
E.g:
verify(mock).someMethod("some arg");
Above is equivalent to:
verify(mock, times(1)).someMethod("some arg");
Arguments passed are compared using equals()
method.
Read about ArgumentCaptor
or ArgumentMatcher
to find out other ways of matching / asserting arguments passed.
Although it is possible to verify a stubbed invocation, usually it's just redundant.
Let's say you've stubbed foo.bar()
.
If your code cares what foo.bar()
returns then something else breaks(often before even verify()
gets executed).
If your code doesn't care what get(0)
returns then it should not be stubbed.
See examples in javadoc for Mockito
class
mock
- to be verifiedpublic static <T> T verify(T mock, VerificationMode mode)
verify(mock, times(5)).someMethod("was called five times");
verify(mock, atLeast(2)).someMethod("was called at least two times");
//you can use flexible argument matchers, e.g:
verify(mock, atLeastOnce()).someMethod(anyString());
times(1) is the default and can be omitted
Arguments passed are compared using equals()
method.
Read about ArgumentCaptor
or ArgumentMatcher
to find out other ways of matching / asserting arguments passed.
mock
- to be verifiedmode
- times(x), atLeastOnce() or never()public static <T> void reset(T... mocks)
Instead of #reset()
please consider writing simple, small and focused test methods over lengthy, over-specified tests.
First potential code smell is reset()
in the middle of the test method. This probably means you're testing too much.
Follow the whisper of your test methods: "Please keep us small & focused on single behavior".
There are several threads about it on mockito mailing list.
The only reason we added reset()
method is to
make it possible to work with container-injected mocks.
For more information see the FAQ (here).
Don't harm yourself. reset()
in the middle of the test method is a code smell (you're probably testing too much).
List mock = mock(List.class);
when(mock.size()).thenReturn(10);
mock.add(1);
reset(mock);
//at this point the mock forgot any interactions & stubbing
T
- The Type of the mocksmocks
- to be resetpublic static <T> void clearInvocations(T... mocks)
T
- The type of the mocksmocks
- The mocks to clear the invocations forpublic static void verifyNoMoreInteractions(Object... mocks)
You can use this method after you verified your mocks - to make sure that nothing else was invoked on your mocks.
See also never()
- it is more explicit and communicates the intent well.
Stubbed invocations (if called) are also treated as interactions.
If you want stubbed invocations automatically verified, check out Strictness.STRICT_STUBS
feature
introduced in Mockito 2.3.0.
If you want to ignore stubs for verification, see ignoreStubs(Object...)
.
A word of warning:
Some users who did a lot of classic, expect-run-verify mocking tend to use verifyNoMoreInteractions()
very often, even in every test method.
verifyNoMoreInteractions()
is not recommended to use in every test method.
verifyNoMoreInteractions()
is a handy assertion from the interaction testing toolkit. Use it only when it's relevant.
Abusing it leads to overspecified, less maintainable tests.
This method will also detect unverified invocations that occurred before the test method,
for example: in setUp()
, @Before
method or in constructor.
Consider writing nice code that makes interactions only in test methods.
Example:
//interactions
mock.doSomething();
mock.doSomethingUnexpected();
//verification
verify(mock).doSomething();
//following will fail because 'doSomethingUnexpected()' is unexpected
verifyNoMoreInteractions(mock);
See examples in javadoc for Mockito
classmocks
- to be verified@Deprecated public static void verifyZeroInteractions(Object... mocks)
verifyNoInteractions(Object...)
verifyNoMoreInteractions(Object...)
.mocks
- to be verifiedpublic static void verifyNoInteractions(Object... mocks)
verifyNoInteractions(mockOne, mockTwo);
This method will also detect invocations
that occurred before the test method, for example: in setUp()
, @Before
method or in constructor.
Consider writing nice code that makes interactions only in test methods.
See also never()
- it is more explicit and communicates the intent well.
See examples in javadoc for Mockito
class
mocks
- to be verifiedpublic static Stubber doThrow(Throwable... toBeThrown)
doThrow()
when you want to stub the void method with an exception.
Stubbing voids requires different approach from when(Object)
because the compiler
does not like void methods inside brackets...
Example:
doThrow(new RuntimeException()).when(mock).someVoidMethod();
toBeThrown
- to be thrown when the stubbed method is calledpublic static Stubber doThrow(Class<? extends Throwable> toBeThrown)
doThrow()
when you want to stub the void method with an exception.
A new exception instance will be created for each method invocation.
Stubbing voids requires different approach from when(Object)
because the compiler
does not like void methods inside brackets...
Example:
doThrow(RuntimeException.class).when(mock).someVoidMethod();
toBeThrown
- to be thrown when the stubbed method is calledpublic static Stubber doThrow(Class<? extends Throwable> toBeThrown, Class<? extends Throwable>... toBeThrownNext)
doThrow(Class)
but sets consecutive exception classes to be thrown. Remember to use
doThrow()
when you want to stub the void method to throw several exception of specified class.
A new exception instance will be created for each method invocation.
Stubbing voids requires different approach from when(Object)
because the compiler
does not like void methods inside brackets...
Example:
doThrow(RuntimeException.class, BigFailure.class).when(mock).someVoidMethod();
toBeThrown
- to be thrown when the stubbed method is calledtoBeThrownNext
- next to be thrown when the stubbed method is calledpublic static Stubber doCallRealMethod()
doCallRealMethod()
when you want to call the real implementation of a method.
As usual you are going to read the partial mock warning: Object oriented programming is more less tackling complexity by dividing the complexity into separate, specific, SRPy objects. How does partial mock fit into this paradigm? Well, it just doesn't... Partial mock usually means that the complexity has been moved to a different method on the same object. In most cases, this is not the way you want to design your application.
However, there are rare cases when partial mocks come handy: dealing with code you cannot change easily (3rd party interfaces, interim refactoring of legacy code etc.) However, I wouldn't use partial mocks for new, test-driven & well-designed code.
See also javadoc spy(Object)
to find out more about partial mocks.
Mockito.spy() is a recommended way of creating partial mocks.
The reason is it guarantees real methods are called against correctly constructed object because you're responsible for constructing the object passed to spy() method.
Example:
Foo mock = mock(Foo.class);
doCallRealMethod().when(mock).someVoidMethod();
// this will call the real implementation of Foo.someVoidMethod()
mock.someVoidMethod();
See examples in javadoc for Mockito
class
public static Stubber doAnswer(Answer answer)
doAnswer()
when you want to stub a void method with generic Answer
.
Stubbing voids requires different approach from when(Object)
because the compiler does not like void methods inside brackets...
Example:
doAnswer(new Answer() {
public Object answer(InvocationOnMock invocation) {
Object[] args = invocation.getArguments();
Mock mock = invocation.getMock();
return null;
}})
.when(mock).someMethod();
See examples in javadoc for Mockito
class
answer
- to answer when the stubbed method is calledpublic static Stubber doNothing()
doNothing()
for setting void methods to do nothing. Beware that void methods on mocks do nothing by default!
However, there are rare situations when doNothing() comes handy:
doNothing().
doThrow(new RuntimeException())
.when(mock).someVoidMethod();
//does nothing the first time:
mock.someVoidMethod();
//throws RuntimeException the next time:
mock.someVoidMethod();
List list = new LinkedList();
List spy = spy(list);
//let's make clear() do nothing
doNothing().when(spy).clear();
spy.add("one");
//clear() does nothing, so the list still contains "one"
spy.clear();
See examples in javadoc for Mockito
class
public static Stubber doReturn(Object toBeReturned)
doReturn()
in those rare occasions when you cannot use when(Object)
.
Beware that when(Object)
is always recommended for stubbing because it is argument type-safe
and more readable (especially when stubbing consecutive calls).
Here are those rare occasions when doReturn() comes handy:
List list = new LinkedList();
List spy = spy(list);
//Impossible: real method is called so spy.get(0) throws IndexOutOfBoundsException (the list is yet empty)
when(spy.get(0)).thenReturn("foo");
//You have to use doReturn() for stubbing:
doReturn("foo").when(spy).get(0);
when(mock.foo()).thenThrow(new RuntimeException());
//Impossible: the exception-stubbed foo() method is called so RuntimeException is thrown.
when(mock.foo()).thenReturn("bar");
//You have to use doReturn() for stubbing:
doReturn("bar").when(mock).foo();
See examples in javadoc for Mockito
class
toBeReturned
- to be returned when the stubbed method is calledpublic static Stubber doReturn(Object toBeReturned, Object... toBeReturnedNext)
doReturn(Object)
but sets consecutive values to be returned. Remember to use
doReturn()
in those rare occasions when you cannot use when(Object)
.
Beware that when(Object)
is always recommended for stubbing because it is argument type-safe
and more readable (especially when stubbing consecutive calls).
Here are those rare occasions when doReturn() comes handy:
List list = new LinkedList();
List spy = spy(list);
//Impossible: real method is called so spy.get(0) throws IndexOutOfBoundsException (the list is yet empty)
when(spy.get(0)).thenReturn("foo", "bar", "qix");
//You have to use doReturn() for stubbing:
doReturn("foo", "bar", "qix").when(spy).get(0);
when(mock.foo()).thenThrow(new RuntimeException());
//Impossible: the exception-stubbed foo() method is called so RuntimeException is thrown.
when(mock.foo()).thenReturn("bar", "foo", "qix");
//You have to use doReturn() for stubbing:
doReturn("bar", "foo", "qix").when(mock).foo();
See examples in javadoc for Mockito
class
toBeReturned
- to be returned when the stubbed method is calledtoBeReturnedNext
- to be returned in consecutive calls when the stubbed method is calledpublic static InOrder inOrder(Object... mocks)
InOrder
object that allows verifying mocks in order.
InOrder inOrder = inOrder(firstMock, secondMock);
inOrder.verify(firstMock).add("was called first");
inOrder.verify(secondMock).add("was called second");
Verification in order is flexible - you don't have to verify all interactions one-by-one
but only those that you are interested in testing in order.
Also, you can create InOrder object passing only mocks that are relevant for in-order verification.
InOrder
verification is 'greedy', but you will hardly ever notice it.
If you want to find out more, read
this wiki page.
As of Mockito 1.8.4 you can verifyNoMoreInteractions() in order-sensitive way. Read more: InOrder.verifyNoMoreInteractions()
See examples in javadoc for Mockito
class
mocks
- to be verified in orderpublic static Object[] ignoreStubs(Object... mocks)
Strictness.STRICT_STUBS
feature which eliminates the need for ignoreStubs()
and provides other benefits.
ignoreStubs()
is sometimes useful when coupled with verifyNoMoreInteractions()
or verification inOrder()
.
Helps avoiding redundant verification of stubbed calls - typically we're not interested in verifying stubs.
Warning, ignoreStubs()
might lead to overuse of verifyNoMoreInteractions(ignoreStubs(...));
Bear in mind that Mockito does not recommend bombarding every test with verifyNoMoreInteractions()
for the reasons outlined in javadoc for verifyNoMoreInteractions(Object...)
Other words: all *stubbed* methods of given mocks are marked *verified* so that they don't get in a way during verifyNoMoreInteractions().
This method changes the input mocks! This method returns input mocks just for convenience.
Ignored stubs will also be ignored for verification inOrder, including InOrder.verifyNoMoreInteractions()
.
See the second example.
Example:
//mocking lists for the sake of the example (if you mock List in real you will burn in hell)
List mock1 = mock(List.class), mock2 = mock(List.class);
//stubbing mocks:
when(mock1.get(0)).thenReturn(10);
when(mock2.get(0)).thenReturn(20);
//using mocks by calling stubbed get(0) methods:
System.out.println(mock1.get(0)); //prints 10
System.out.println(mock2.get(0)); //prints 20
//using mocks by calling clear() methods:
mock1.clear();
mock2.clear();
//verification:
verify(mock1).clear();
verify(mock2).clear();
//verifyNoMoreInteractions() fails because get() methods were not accounted for.
try { verifyNoMoreInteractions(mock1, mock2); } catch (NoInteractionsWanted e);
//However, if we ignore stubbed methods then we can verifyNoMoreInteractions()
verifyNoMoreInteractions(ignoreStubs(mock1, mock2));
//Remember that ignoreStubs() *changes* the input mocks and returns them for convenience.
Ignoring stubs can be used with verification in order:
List list = mock(List.class);
when(list.get(0)).thenReturn("foo");
list.add(0);
list.clear();
System.out.println(list.get(0)); //we don't want to verify this
InOrder inOrder = inOrder(ignoreStubs(list));
inOrder.verify(list).add(0);
inOrder.verify(list).clear();
inOrder.verifyNoMoreInteractions();
Stubbed invocations are automatically verified with Strictness.STRICT_STUBS
feature
and it eliminates the need for ignoreStubs()
. Example below uses JUnit Rules:
@Rule public MockitoRule mockito = MockitoJUnit.rule().strictness(Strictness.STRICT_STUBS);
List list = mock(List.class);
when(list.get(0)).thenReturn("foo");
list.size();
verify(list).size();
list.get(0); // Automatically verified by STRICT_STUBS
verifyNoMoreInteractions(list); // No need of ignoreStubs()
mocks
- input mocks that will be changedpublic static VerificationMode times(int wantedNumberOfInvocations)
verify(mock, times(2)).someMethod("some arg");
See examples in javadoc for Mockito
classwantedNumberOfInvocations
- wanted number of invocationspublic static VerificationMode never()
times(0)
, see times(int)
Verifies that interaction did not happen. E.g:
verify(mock, never()).someMethod();
If you want to verify there were NO interactions with the mock
check out verifyZeroInteractions(Object...)
or verifyNoMoreInteractions(Object...)
See examples in javadoc for Mockito
class
public static VerificationMode atLeastOnce()
verify(mock, atLeastOnce()).someMethod("some arg");
Alias to atLeast(1)
.
See examples in javadoc for Mockito
class
public static VerificationMode atLeast(int minNumberOfInvocations)
verify(mock, atLeast(3)).someMethod("some arg");
See examples in javadoc for Mockito
classminNumberOfInvocations
- minimum number of invocationspublic static VerificationMode atMostOnce()
verify(mock, atMostOnce()).someMethod("some arg");
Alias to atMost(1)
.
See examples in javadoc for Mockito
class
public static VerificationMode atMost(int maxNumberOfInvocations)
verify(mock, atMost(3)).someMethod("some arg");
See examples in javadoc for Mockito
classmaxNumberOfInvocations
- max number of invocationspublic static VerificationMode calls(int wantedNumberOfInvocations)
inOrder.verify( mock, calls( 2 )).someMethod( "some arg" );
wantedNumberOfInvocations
- number of invocations to verifypublic static VerificationMode only()
verify(mock, only()).someMethod();
//above is a shorthand for following 2 lines of code:
verify(mock).someMethod();
verifyNoMoreInteractions(mock);
See also verifyNoMoreInteractions(Object...)
See examples in javadoc for Mockito
class
public static VerificationWithTimeout timeout(long millis)
timeout()
method can be a code smell - there are better ways of testing concurrent code.
See also after(long)
method for testing async code.
Differences between timeout()
and after
are explained in Javadoc for after(long)
.
//passes when someMethod() is called no later than within 100 ms
//exits immediately when verification is satisfied (e.g. may not wait full 100 ms)
verify(mock, timeout(100)).someMethod();
//above is an alias to:
verify(mock, timeout(100).times(1)).someMethod();
//passes as soon as someMethod() has been called 2 times under 100 ms
verify(mock, timeout(100).times(2)).someMethod();
//equivalent: this also passes as soon as someMethod() has been called 2 times under 100 ms
verify(mock, timeout(100).atLeast(2)).someMethod();
See examples in javadoc for Mockito
classmillis
- - duration in millisecondspublic static VerificationAfterDelay after(long millis)
after()
method can be a code smell - there are better ways of testing concurrent code.
Not yet implemented to work with InOrder verification.
See also timeout(long)
method for testing async code.
Differences between timeout()
and after()
are explained below.
//passes after 100ms, if someMethod() has only been called once at that time.
verify(mock, after(100)).someMethod();
//above is an alias to:
verify(mock, after(100).times(1)).someMethod();
//passes if someMethod() is called *exactly* 2 times, as tested after 100 millis
verify(mock, after(100).times(2)).someMethod();
//passes if someMethod() has not been called, as tested after 100 millis
verify(mock, after(100).never()).someMethod();
//verifies someMethod() after a given time span using given verification mode
//useful only if you have your own custom verification modes.
verify(mock, new After(100, yourOwnVerificationMode)).someMethod();
timeout() vs. after()
//1.
mock.foo();
verify(mock, after(1000)).foo();
//waits 1000 millis and succeeds
//2.
mock.foo();
verify(mock, timeout(1000)).foo();
//succeeds immediately
See examples in javadoc for Mockito
classmillis
- - duration in millisecondspublic static void validateMockitoUsage()
In case of questions you may also post to mockito mailing list: http://groups.google.com/group/mockito
validateMockitoUsage()
explicitly validates the framework state to detect invalid use of Mockito.
However, this feature is optional because Mockito validates the usage all the time... but there is a gotcha so read on.
Examples of incorrect use:
//Oops, thenReturn() part is missing:
when(mock.get());
//Oops, verified method call is inside verify() where it should be on the outside:
verify(mock.execute());
//Oops, missing method to verify:
verify(mock);
Mockito throws exceptions if you misuse it so that you know if your tests are written correctly.
The gotcha is that Mockito does the validation next time you use the framework (e.g. next time you verify, stub, call mock etc.).
But even though the exception might be thrown in the next test,
the exception message contains a navigable stack trace element with location of the defect.
Hence you can click and find the place where Mockito was misused.
Sometimes though, you might want to validate the framework usage explicitly.
For example, one of the users wanted to put validateMockitoUsage()
in his @After
method
so that he knows immediately when he misused Mockito.
Without it, he would have known about it not sooner than next time he used the framework.
One more benefit of having validateMockitoUsage()
in @After
is that jUnit runner and rule will always fail in the test method with defect
whereas ordinary 'next-time' validation might fail the next test method.
But even though JUnit might report next test as red, don't worry about it
and just click at navigable stack trace element in the exception message to instantly locate the place where you misused mockito.
Both built-in runner: MockitoJUnitRunner
and rule: MockitoRule
do validateMockitoUsage() after each test method.
Bear in mind that usually you don't have to validateMockitoUsage()
and framework validation triggered on next-time basis should be just enough,
mainly because of enhanced exception message with clickable location of defect.
However, I would recommend validateMockitoUsage() if you already have sufficient test infrastructure
(like your own runner or base class for all tests) because adding a special action to @After
has zero cost.
See examples in javadoc for Mockito
class
public static MockSettings withSettings()
Don't use it too often. Consider writing simple tests that use simple mocks. Repeat after me: simple tests push simple, KISSy, readable & maintainable code. If you cannot write a test in a simple way - refactor the code under test.
Examples of mock settings:
//Creates mock with different default answer & name
Foo mock = mock(Foo.class, withSettings()
.defaultAnswer(RETURNS_SMART_NULLS)
.name("cool mockie"));
//Creates mock with different default answer, descriptive name and extra interfaces
Foo mock = mock(Foo.class, withSettings()
.defaultAnswer(RETURNS_SMART_NULLS)
.name("cool mockie")
.extraInterfaces(Bar.class));
MockSettings
has been introduced for two reasons.
Firstly, to make it easy to add another mock settings when the demand comes.
Secondly, to enable combining different mock settings without introducing zillions of overloaded mock() methods.
See javadoc for MockSettings
to learn about possible mock settings.
public static VerificationMode description(String description)
verify(mock, description("This will print on failure")).someMethod("some arg");
description
- The description to print on failure.@Incubating public static MockitoFramework framework()
MockitoFramework
class.@Incubating public static MockitoSessionBuilder mockitoSession()
MockitoSession
is an optional, highly recommended feature
that helps driving cleaner tests by eliminating boilerplate code and adding extra validation.
For more information, including use cases and sample code, see the javadoc for MockitoSession
.
@Incubating public static LenientStubber lenient()
Strictness.STRICT_STUBS
).
When stubbing is declared as lenient, it will not be checked for potential stubbing problems such as
'unnecessary stubbing' (UnnecessaryStubbingException
) or for 'stubbing argument mismatch' PotentialStubbingProblem
.
lenient().when(mock.foo()).thenReturn("ok");
Most mocks in most tests don't need leniency and should happily prosper with Strictness.STRICT_STUBS
.
MockSettings.lenient()
MockitoJUnit
or Mockito Session (MockitoSession
)This example is simplified and not realistic. Pushing stubbings to 'before()' method may cause tests to be less readable. Some repetition in tests is OK, use your own judgement to write great tests! It is not desired to eliminate all possible duplication from the test code because it may add complexity and conceal important test information.
public class SomeTest {
@Rule public MockitoRule mockito = MockitoJUnit.rule().strictness(STRICT_STUBS);
@Mock Foo foo;
@Mock Bar bar;
@Before public void before() {
when(foo.foo()).thenReturn("ok");
// it is better to configure the stubbing to be lenient:
// lenient().when(foo.foo()).thenReturn("ok");
// or the entire mock to be lenient:
// foo = mock(Foo.class, withSettings().lenient());
}
@Test public void test1() {
foo.foo();
}
@Test public void test2() {
foo.foo();
}
@Test public void test3() {
bar.bar();
}
}