Final method mocking - java

I need mock some class with final method using mockito. I have wrote something like this
#Test
public void test() {
B b = mock(B.class);
doReturn("bar called").when(b).bar();
assertEquals("must be \"overrided\"", "bar called", b.bar());
//bla-bla
}
class B {
public final String bar() {
return "fail";
}
}
But it fails.
I tried some "hack" and it works.
#Test
public void hackTest() {
class NewB extends B {
public String barForTest() {
return bar();
}
}
NewB b = mock(NewB.class);
doReturn("bar called").when(b).barForTest();
assertEquals("must be \"overrided\"", "bar called", b.barForTest());
}
It works, but "smells".
So, Where is the right way?
Thanks.

From the Mockito FAQ:
What are the limitations of Mockito
Cannot mock final methods - their real behavior is executed without any exception. Mockito cannot warn you about mocking final methods so be vigilant.

There is no support for mocking final methods in Mockito.
As Jon Skeet commented you should be looking for a way to avoid the dependency on the final method. That said, there are some ways out through bytecode manipulation (e.g. with PowerMock)
A comparison between Mockito and PowerMock will explain things in detail.

You can use Powermock together with Mockito, then you do not need to subclass B.class. Just add this to the top of your test class
#RunWith(PowerMockRunner.class)
#PrepareForTest(B.class)
#PrepareForTest instructs Powermock to instrument B.class to make the final and static methods mockable. A disadvantage of this approach is that you must use PowerMockRunner which precludes use of other test runners such as the Spring test runner.

Mockito 2 now supports mocking final methods but that's an "incubating" feature. It requires some steps to activate it which are described here:
https://github.com/mockito/mockito/wiki/What's-new-in-Mockito-2#mock-the-unmockable-opt-in-mocking-of-final-classesmethods

Mockito 2.x now supports final method and final class stubbing.
From the docs:
Mocking of final classes and methods is an incubating, opt-in feature. This feature has to be explicitly activated by creating the file src/test/resources/mockito-extensions/org.mockito.plugins.MockMaker containing a single line:
mock-maker-inline
After you create this file you can do:
final class FinalClass {
final String finalMethod() { return "something"; }
}
FinalClass concrete = new FinalClass();
FinalClass mock = mock(FinalClass.class);
given(mock.finalMethod()).willReturn("not anymore");
assertThat(mock.finalMethod()).isNotEqualTo(concrete.finalMethod());
In subsequent milestones, the team will bring a programmatic way of using this feature. We will identify and provide support for all unmockable scenarios.

Assuming that B class is as below:
class B {
private String barValue;
public final String bar() {
return barValue;
}
public void final setBar(String barValue) {
this.barValue = barValue;
}
}
There is a better way to do this without using PowerMockito framework.
You can create a SPY for your class and can mock your final method.
Below is the way to do it:
#Test
public void test() {
B b = new B();
b.setBar("bar called") //This should the expected output:final_method_bar()
B spyB = Mockito.spy(b);
assertEquals("bar called", spyB.bar());
}

Mockito can be used to mock final classes or final methods. The problem is, this doesn't come as out of the box feature from Mockito and needs to be configured explicitely.
So, in order to do that,
Create a text file named org.mockito.plugins.MockMaker to the project's src/test/resources/mockito-extensions directory and add a single line of text as below
mock-maker-inline
Once done, you can use the mockito's when method to mock the behaviour like any other regular method.
See detailed examples here

I just did this same thing. My case was that I wanted to ensure the method didn't cause an error. But, since it's a catch/log/return method, I couldn't test for it directly without modifying the class.
I wanted to simply mock the logger I passed in. But, something about mocking the Log interface didn't seem to work, and mocking a class like SimpleLog didn't work because those methods are final.
I ended up creating an anonymous inner class extending SimpleLog that overrode the base-level log(level, string, error) method that the others all delegate to. Then the test is just waiting for a call with a level of 5.
In general, extending a class for behavior isn't really a bad idea, and might be preferable to mocking anyway if it's not too complicated.

Related

Spring Mockito Mocked object keeps calling real method [duplicate]

I need mock some class with final method using mockito. I have wrote something like this
#Test
public void test() {
B b = mock(B.class);
doReturn("bar called").when(b).bar();
assertEquals("must be \"overrided\"", "bar called", b.bar());
//bla-bla
}
class B {
public final String bar() {
return "fail";
}
}
But it fails.
I tried some "hack" and it works.
#Test
public void hackTest() {
class NewB extends B {
public String barForTest() {
return bar();
}
}
NewB b = mock(NewB.class);
doReturn("bar called").when(b).barForTest();
assertEquals("must be \"overrided\"", "bar called", b.barForTest());
}
It works, but "smells".
So, Where is the right way?
Thanks.
From the Mockito FAQ:
What are the limitations of Mockito
Cannot mock final methods - their real behavior is executed without any exception. Mockito cannot warn you about mocking final methods so be vigilant.
There is no support for mocking final methods in Mockito.
As Jon Skeet commented you should be looking for a way to avoid the dependency on the final method. That said, there are some ways out through bytecode manipulation (e.g. with PowerMock)
A comparison between Mockito and PowerMock will explain things in detail.
You can use Powermock together with Mockito, then you do not need to subclass B.class. Just add this to the top of your test class
#RunWith(PowerMockRunner.class)
#PrepareForTest(B.class)
#PrepareForTest instructs Powermock to instrument B.class to make the final and static methods mockable. A disadvantage of this approach is that you must use PowerMockRunner which precludes use of other test runners such as the Spring test runner.
Mockito 2 now supports mocking final methods but that's an "incubating" feature. It requires some steps to activate it which are described here:
https://github.com/mockito/mockito/wiki/What's-new-in-Mockito-2#mock-the-unmockable-opt-in-mocking-of-final-classesmethods
Mockito 2.x now supports final method and final class stubbing.
From the docs:
Mocking of final classes and methods is an incubating, opt-in feature. This feature has to be explicitly activated by creating the file src/test/resources/mockito-extensions/org.mockito.plugins.MockMaker containing a single line:
mock-maker-inline
After you create this file you can do:
final class FinalClass {
final String finalMethod() { return "something"; }
}
FinalClass concrete = new FinalClass();
FinalClass mock = mock(FinalClass.class);
given(mock.finalMethod()).willReturn("not anymore");
assertThat(mock.finalMethod()).isNotEqualTo(concrete.finalMethod());
In subsequent milestones, the team will bring a programmatic way of using this feature. We will identify and provide support for all unmockable scenarios.
Assuming that B class is as below:
class B {
private String barValue;
public final String bar() {
return barValue;
}
public void final setBar(String barValue) {
this.barValue = barValue;
}
}
There is a better way to do this without using PowerMockito framework.
You can create a SPY for your class and can mock your final method.
Below is the way to do it:
#Test
public void test() {
B b = new B();
b.setBar("bar called") //This should the expected output:final_method_bar()
B spyB = Mockito.spy(b);
assertEquals("bar called", spyB.bar());
}
Mockito can be used to mock final classes or final methods. The problem is, this doesn't come as out of the box feature from Mockito and needs to be configured explicitely.
So, in order to do that,
Create a text file named org.mockito.plugins.MockMaker to the project's src/test/resources/mockito-extensions directory and add a single line of text as below
mock-maker-inline
Once done, you can use the mockito's when method to mock the behaviour like any other regular method.
See detailed examples here
I just did this same thing. My case was that I wanted to ensure the method didn't cause an error. But, since it's a catch/log/return method, I couldn't test for it directly without modifying the class.
I wanted to simply mock the logger I passed in. But, something about mocking the Log interface didn't seem to work, and mocking a class like SimpleLog didn't work because those methods are final.
I ended up creating an anonymous inner class extending SimpleLog that overrode the base-level log(level, string, error) method that the others all delegate to. Then the test is just waiting for a call with a level of 5.
In general, extending a class for behavior isn't really a bad idea, and might be preferable to mocking anyway if it's not too complicated.

Why Cannot I use Mock and InjectMocks together?

valid construction:
#InjectMocks
SomeClass sc = mock(SomeClass.class);
Invalid construction:
#InjectMocks
#Mock
SomeClass sc;
I want to inject mocks to another mock. I want to use only annotation style.
Why was in Mockito forbid second construction ?
Update
example:
public class ArrTest {
private SomeClass someClass;
public List<String> foo(){
anotherMethod(); // I suppose that this method works. I want to test it separately.
//logic which I need to test
return someClass.doSmth();// I suppose that this method works. I want to test it separately.
}
public void anotherMethod(){
///...
}
}
public class SomeClass {
public List<String> doSmth(){
return null;
}
}
test:
public class ArrTestTest {
#InjectMocks
ArrTest arrTest = Mockito.mock(ArrTest.class);
#Mock
SomeClass someClass;
#Test
public void fooTest(){
Mockito.when(someClass.doSmth()).thenReturn(new ArrayList<String>());
Mockito.doNothing().when(arrTest).anotherMethod();
System.out.println(arrTest.foo());
}
}
It sounds like you're trying to do something that doesn't really make sense. You shouldn't need to inject any dependencies into your mock since mocks by definition don't have any behaviour until you define it with when(mock.someMethod()).thenAnswer() or some variation.
(except perhaps if you're using a spy(), but you've specifically said you're using a #Mock).
Maybe you could explain your use case and why you're trying to inject dependencies into a mock?
#InjectMocks specifically indicates that the annotated field will NOT contain a mock. Annotating #InjectMocks #Mock is not just unsupported—it's contradictory.
To return stubs wherever possible, use this:
#Mock(answer=Answers.RETURNS_DEEP_STUBS)
YourClass mockYourClassWithDeepStubs;
But heed the official documentation for this Answer:
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.
A mock doesn't have any real implementation. #InjectMocks would try to find and call setters for whatever mock objects have already been created and pass them in. Mockito "knows" that this is kinda pointless on a mock, since there won't be any way to get the mock objects back out, much less do anything meaningful with them.

NotAMockException while Mockito.verify(Object,VerificationMode.atleast(2))

I am using mockito for mock the unit test cases and am getting the following exception
org.mockito.exceptions.misusing.NotAMockException:
Argument passed to verify() is of type ConsumerImpl and is not a mock!
Make sure you place the parenthesis correctly!
See the examples of correct verifications:
verify(mock).someMethod();
verify(mock, times(10)).someMethod();
verify(mock, atLeastOnce()).someMetenter code herehod();
and my code is
MessageConsumer mConsumer = Mockito.mock(MessageConsumer.class);
String data = "new Message for Testing";
Message message = new Message(data.getBytes());
Mockito.when(mConsumer.next(10, TimeUnit.SECONDS)).thenReturn(message);
StringParserTest parserTest = new StringParserTest();
ConsumerImpl<String> consumer = new ConsumerImpl<String>(mConsumer, parserTest);
String mes=Mockito.verify(consumer,VerificationModeFactory.times(3)).consumeMessage(10,TimeUnit.SECONDS);
Please some one help me to solve this problem
Thanks in Advance
SRN
Well, that's exactly what mockito says, you are not passing a mock to verify !
ConsumerImpl<String> consumer = new ConsumerImpl<String>(mConsumer, parserTest);
String mes=Mockito.verify(consumer,VerificationModeFactory.times(3)).consumeMessage(10,TimeUnit.SECONDS);
Plus if you verified a mock why would you want to store the result of the invocation you verify, it wouldn't make sense since the consumer is mocked. Verify is to verify calls on mocked objects that are the collaborators of your unit tested object. Which in your case is not really clear.
Also you never use your mock mConsumer instance.
You should definitely separate your test in 3 phase, one for the fixture, one for the action, and one for the verifications. Use the BDD terminology to achieve that, it augments understanding and readability for the tester and future reader of this code (And Mockito offers them in the API through BDDMockito).
As I don't really get what the code is trying to test from the code you gave, I'll be imagining things. So for example you'll write this kind of code (using import static) :
// given a consumer
MessageConsumer message_consumer = mock(MessageConsumer.class);
String the_message_data = "new Message for Testing";
given(message_consumer.next(10, SECONDS)).willReturn(new Message(the_message_data.getBytes()));
// when calling the client of the customer (which is the unit that is tested)
new MessageProcessor(message_consumer).processAll();
// then verify that consumeMessage is called 3 times
verify(message_consumer, times(3)).consumeMessage(10, SECONDS);
Remember Mockito helps you focus on interactions between objects — as it's the most important notion of object oriented programming — and especially between the tested one and his collaborators that will certainly be mocked.
Usually we mock using #InjectMock and we try to verify a method called from inside the test case method.
Here is one scenario which generally give issue.
public class A{
#Autowired
Service s
public void method1(){
method2();
}
public void method2(){
s.someMethod();
}
}
public class ATest{
#InjectMocks
A a;
public void testM1(){
a.method1();
Mockito.verify(a, Mockito.times(1)).method2();
}
}
This will always give "NoAMockException while Mockito.verify"
instead of that we should use following verification.
public class ATest{
#InjectMocks
A a;
#Mock
Service s
public void testM1(){
a.method1();
Mockito.verify(s, Mockito.times(1)).someMethod();
}
}
Or if we want to verify() method2()
then we have to #Mock class A instead of #InjectMock

How to mock a final class with mockito

I have a final class, something like this:
public final class RainOnTrees{
public void startRain(){
// some code here
}
}
I am using this class in some other class like this:
public class Seasons{
RainOnTrees rain = new RainOnTrees();
public void findSeasonAndRain(){
rain.startRain();
}
}
and in my JUnit test class for Seasons.java I want to mock the RainOnTrees class. How can I do this with Mockito?
Mocking final/static classes/methods is possible with Mockito v2 only.
add this in your gradle file:
testImplementation 'org.mockito:mockito-inline:2.13.0'
This is not possible with Mockito v1, from the Mockito FAQ:
What are the limitations of Mockito
Needs java 1.5+
Cannot mock final classes
...
Mockito 2 now supports final classes and methods!
But for now that's an "incubating" feature. It requires some steps to activate it which are described in What's New in Mockito 2:
Mocking of final classes and methods is an incubating, opt-in feature. It uses a combination of Java agent instrumentation and subclassing in order to enable mockability of these types. As this works differently to our current mechanism and this one has different limitations and as we want to gather experience and user feedback, this feature had to be explicitly activated to be available ; it can be done via the mockito extension mechanism by creating the file src/test/resources/mockito-extensions/org.mockito.plugins.MockMaker containing a single line:
mock-maker-inline
After you created this file, Mockito will automatically use this new engine and one can do :
final class FinalClass {
final String finalMethod() { return "something"; }
}
FinalClass concrete = new FinalClass();
FinalClass mock = mock(FinalClass.class);
given(mock.finalMethod()).willReturn("not anymore");
assertThat(mock.finalMethod()).isNotEqualTo(concrete.finalMethod());
In subsequent milestones, the team will bring a programmatic way of using this feature. We will identify and provide support for all unmockable scenarios. Stay tuned and please let us know what you think of this feature!
add this in your build file:
if using gradle: build.gradle
testImplementation 'org.mockito:mockito-inline:2.13.0'
if using maven: pom.xml
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-inline</artifactId>
<version>2.13.0</version>
<scope>test</scope>
</dependency>
this is a configuration to make mockito work with final classes
If you faced the Could not initialize inline Byte Buddy mock maker. (This mock maker is not supported on Android.)
Add the Byte Buddy dependency to your build.gradle file:
testImplementation 'net.bytebuddy:byte-buddy-agent:1.10.19'
src: https://mvnrepository.com/artifact/net.bytebuddy/byte-buddy
You cannot mock a final class with Mockito, as you can't do it by yourself.
What I do, is to create a non-final class to wrap the final class and use as delegate. An example of this is TwitterFactory class, and this is my mockable class:
public class TwitterFactory {
private final twitter4j.TwitterFactory factory;
public TwitterFactory() {
factory = new twitter4j.TwitterFactory();
}
public Twitter getInstance(User user) {
return factory.getInstance(accessToken(user));
}
private AccessToken accessToken(User user) {
return new AccessToken(user.getAccessToken(), user.getAccessTokenSecret());
}
public Twitter getInstance() {
return factory.getInstance();
}
}
The disadvantage is that there is a lot of boilerplate code; the advantage is that you can add some methods that may relate to your application business (like the getInstance that is taking a user instead of an accessToken, in the above case).
In your case I would create a non-final RainOnTrees class that delegate to the final class. Or, if you can make it non-final, it would be better.
In Mockito 3 and more I have the same problem and fixed it as from this link
Mock Final Classes and Methods with Mockito
as follow
Before Mockito can be used for mocking final classes and methods, it needs to be > configured.
We need to add a text file to the project's src/test/resources/mockito-extensions directory named org.mockito.plugins.MockMaker and add a single line of text:
mock-maker-inline
Mockito checks the extensions directory for configuration files when it is loaded. This file enables the mocking of final methods and classes.
Use Powermock. This link shows, how to do it: https://github.com/jayway/powermock/wiki/MockFinal
Just to follow up. Please add this line to your gradle file:
testCompile group: 'org.mockito', name: 'mockito-inline', version: '2.8.9'
I have tried various version of mockito-core and mockito-all. Neither of them work.
I had the same problem. Since the class I was trying to mock was a simple class, I simply created an instance of it and returned that.
I guess you made it final because you want to prevent other classes from extending RainOnTrees. As Effective Java suggests (item 15), there's another way to keep a class close for extension without making it final:
Remove the final keyword;
Make its constructor private. No class will be able to extend it because it won't be able to call the super constructor;
Create a static factory method to instantiate your class.
// No more final keyword here.
public class RainOnTrees {
public static RainOnTrees newInstance() {
return new RainOnTrees();
}
private RainOnTrees() {
// Private constructor.
}
public void startRain() {
// some code here
}
}
By using this strategy, you'll be able to use Mockito and keep your class closed for extension with little boilerplate code.
Another workaround, which may apply in some cases, is to create an interface that is implemented by that final class, change the code to use the interface instead of the concrete class and then mock the interface. This lets you separate the contract (interface) from the implementation (final class). Of course, if what you want is really to bind to the final class, this will not apply.
Time saver for people who are facing the same issue (Mockito + Final Class) on Android + Kotlin. As in Kotlin classes are final by default. I found a solution in one of Google Android samples with Architecture component. Solution picked from here : https://github.com/googlesamples/android-architecture-components/blob/master/GithubBrowserSample
Create following annotations :
/**
* This annotation allows us to open some classes for mocking purposes while they are final in
* release builds.
*/
#Target(AnnotationTarget.ANNOTATION_CLASS)
annotation class OpenClass
/**
* Annotate a class with [OpenForTesting] if you want it to be extendable in debug builds.
*/
#OpenClass
#Target(AnnotationTarget.CLASS)
annotation class OpenForTesting
Modify your gradle file. Take example from here : https://github.com/googlesamples/android-architecture-components/blob/master/GithubBrowserSample/app/build.gradle
apply plugin: 'kotlin-allopen'
allOpen {
// allows mocking for classes w/o directly opening them for release builds
annotation 'com.android.example.github.testing.OpenClass'
}
Now you can annotate any class to make it open for testing :
#OpenForTesting
class RepoRepository
Actually there is one way, which I use for spying. It would work for you only if two preconditions are satisfied:
You use some kind of DI to inject an instance of final class
Final class implements an interface
Please recall Item 16 from Effective Java. You may create a wrapper (not final) and forward all call to the instance of final class:
public final class RainOnTrees implement IRainOnTrees {
#Override public void startRain() { // some code here }
}
public class RainOnTreesWrapper implement IRainOnTrees {
private IRainOnTrees delegate;
public RainOnTreesWrapper(IRainOnTrees delegate) {this.delegate = delegate;}
#Override public void startRain() { delegate.startRain(); }
}
Now not only can you mock your final class but also spy on it:
public class Seasons{
RainOnTrees rain;
public Seasons(IRainOnTrees rain) { this.rain = rain; };
public void findSeasonAndRain(){
rain.startRain();
}
}
IRainOnTrees rain = spy(new RainOnTreesWrapper(new RainOnTrees()) // or mock(IRainOnTrees.class)
doNothing().when(rain).startRain();
new Seasons(rain).findSeasonAndRain();
Give this a try:
Mockito.mock(SomeMockableType.class,AdditionalAnswers.delegatesTo(someInstanceThatIsNotMockableOrSpyable));
It worked for me. "SomeMockableType.class" is the parent class of what you want to mock or spy, and someInstanceThatIsNotMockableOrSpyable is the actual class that you want to mock or spy.
For more details have a look here
This can be done if you are using Mockito2, with the new incubating feature which supports mocking of final classes & methods.
Key points to note:
1. Create a simple file with the name “org.mockito.plugins.MockMaker” and place it in a folder named “mockito-extensions”. This folder should be made available on the classpath.
2. The content of the file created above should be a single line as given below:
mock-maker-inline
The above two steps are required in order to activate the mockito extension mechanism and use this opt-in feature.
Sample classes are as follows:-
FinalClass.java
public final class FinalClass {
public final String hello(){
System.out.println("Final class says Hello!!!");
return "0";
}
}
Foo.java
public class Foo {
public String executeFinal(FinalClass finalClass){
return finalClass.hello();
}
}
FooTest.java
public class FooTest {
#Test
public void testFinalClass(){
// Instantiate the class under test.
Foo foo = new Foo();
// Instantiate the external dependency
FinalClass realFinalClass = new FinalClass();
// Create mock object for the final class.
FinalClass mockedFinalClass = mock(FinalClass.class);
// Provide stub for mocked object.
when(mockedFinalClass.hello()).thenReturn("1");
// assert
assertEquals("0", foo.executeFinal(realFinalClass));
assertEquals("1", foo.executeFinal(mockedFinalClass));
}
}
Hope it helps.
Complete article present here mocking-the-unmockable.
Yes same problem here, we cannot mock a final class with Mockito. To be accurate, Mockito cannot mock/spy following:
final classes
anonymous classes
primitive types
But using a wrapper class seems to me a big price to pay, so get PowerMockito instead.
I think you need think more in principle. Instead you final class use his interface and mock interface instead.
For this:
public class RainOnTrees{
fun startRain():Observable<Boolean>{
// some code here
}
}
add
interface iRainOnTrees{
public void startRain():Observable<Boolean>
}
and mock you interface:
#Before
fun setUp() {
rainService= Mockito.mock(iRainOnTrees::class.java)
`when`(rainService.startRain()).thenReturn(
just(true).delay(3, TimeUnit.SECONDS)
)
}
Please look at JMockit. It has extensive documentation with a lot of examples. Here you have an example solution of your problem (to simplify I've added constructor to Seasons to inject mocked RainOnTrees instance):
package jmockitexample;
import mockit.Mocked;
import mockit.Verifications;
import mockit.integration.junit4.JMockit;
import org.junit.Test;
import org.junit.runner.RunWith;
#RunWith(JMockit.class)
public class SeasonsTest {
#Test
public void shouldStartRain(#Mocked final RainOnTrees rain) {
Seasons seasons = new Seasons(rain);
seasons.findSeasonAndRain();
new Verifications() {{
rain.startRain();
}};
}
public final class RainOnTrees {
public void startRain() {
// some code here
}
}
public class Seasons {
private final RainOnTrees rain;
public Seasons(RainOnTrees rain) {
this.rain = rain;
}
public void findSeasonAndRain() {
rain.startRain();
}
}
}
Solutions provided by RC and Luigi R. Viggiano together is possibly the best idea.
Although Mockito cannot, by design, mock final classes, the delegation approach is possible. This has its advantages:
You are not forced to change your class to non-final if that is what your API intends in the first place (final classes have their benefits).
You are testing the possibility of a decoration around your API.
In your test case, you deliberately forward the calls to the system under test. Hence, by design, your decoration does not do anything.
Hence you test can also demonstrate that the user can only decorate the API instead of extending it.
On a more subjective note:
I prefer keeping the frameworks to a minimum, which is why JUnit and Mockito are usually sufficient for me. In fact, restricting this way sometimes forces me to refactor for good as well.
If you trying to run unit-test under the test folder, the top solution is fine. Just follow it adding an extension.
But if you want to run it with android related class like context or activity which is under androidtest folder, the answer is for you.
Add these dependencies for run mockito successfully :
testImplementation 'org.mockito:mockito-core:2.24.5'
testImplementation "org.mockito:mockito-inline:2.24.5"
Mocking final classes is not supported for mockito-android as per this GitHub issue. You should use Mockk instead for this.
For both unit test and ui test, you can use Mockk with no problem.
If you need to use Mockito in an instrumented test in Android (i. e. running in an Android device), you cannot use mockito-inline. There is a special mockito-android version which doesn't solve the "final class" problem either. The only solution which seems to work is the Dexmaker library. The only limitation is that it works only in Android P (Android 9, API 28) and higher. It can be imported as follows:
androidTestImplementation "com.linkedin.dexmaker:dexmaker-mockito-inline:2.28.1"
Beware that there is also a "dexmaker-mockito" version which doesn't work for final classes either. Make sure you import "dexmaker-mockito-inline".
As others have stated, this won't work out of the box with Mockito. I would suggest using reflection to set the specific fields on the object that is being used by the code under test. If you find yourself doing this a lot, you can wrap this functionality in a library.
As an aside, if you are the one marking classes final, stop doing that. I ran across this question because I am working with an API where everything was marked final to prevent my legitimate need for extension (mocking), and I wish that the developer had not assumed that I would never need to extend the class.
For us, it was because we excluded mockito-inline from koin-test. One gradle module actually needed this and for reason only failed on release builds (debug builds in the IDE worked) :-P
For final class add below to mock and call static or non static.
1- add this in class level
#SuppressStatucInitializationFor(value ={class name with package})
2- PowerMockito.mockStatic(classname.class) will mock class
3- then use your when statement to return mock object when calling method of this class.
Enjoy
I was able to overcome this message:
org.mockito.exceptions.base.MockitoException:
Cannot mock/spy class org.slf4j.impl.Log4jLoggerAdapter
Mockito cannot mock/spy because :
final or anonymous class
from this: log = spy(log);
By using this instead:
log = mock(Logger.class);
Then it works.
I guess that "default" logger adapter is an instance of a final class so I couldn't "spy" it, but I could mock the whole thing. Go figure...
This may mean that you could substitute it for some other "non final" instance if you have that handy, as well. Or a simplified version, etc. FWIW...
I am writing the steps I followed after various unsuccessful attempts to mock final/private classes and their methods in Java 11, which finally worked for me.
Create a file named org.mockito.plugins.MockMaker inside
your test/resources/mockito-extensions folder. Please create
mockito-extensions folder if not present already.
Add a single line mock-maker-inline as the content of the above org.mockito.plugins.MockMaker file
Add
#RunWith(PowerMockRunner.class)
#PowerMockIgnore({"javax.management.*", "jdk.internal.reflect.*", "com.sun.org.apache.xerces.*", "javax.xml.*", "org.xml.*", "org.w3c.*"})
#PrepareForTest(Utility.class)
annotations at the class level.
Setup process in the test class
#Before
public void setup () {
MockitoAnnotations.initMocks(this);
Mockito.mockStatic(ClassToBeMocked.class);
}
Use Mockito.when(..).thenReturn(..) for assertions
In case of multiple test cases, add the below code
#After
public void after() {
Mockito.framework().clearInlineMocks();
}
The mockito version which I am using: 3.9.0
Java version: 11
Didn't try final, but for private, using reflection remove the modifier worked ! have checked further, it doesn't work for final.

Mockito: Trying to spy on method is calling the original method

I'm using Mockito 1.9.0. I want mock the behaviour for a single method of a class in a JUnit test, so I have
final MyClass myClassSpy = Mockito.spy(myInstance);
Mockito.when(myClassSpy.method1()).thenReturn(myResults);
The problem is, in the second line, myClassSpy.method1() is actually getting called, resulting in an exception. The only reason I'm using mocks is so that later, whenever myClassSpy.method1() is called, the real method won't be called and the myResults object will be returned.
MyClass is an interface and myInstance is an implementation of that, if that matters.
What do I need to do to correct this spying behaviour?
Let me quote the official documentation:
Important gotcha on spying real objects!
Sometimes it's impossible to use when(Object) for stubbing spies. 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);
In your case it goes something like:
doReturn(resultsIWant).when(myClassSpy).method1();
In my case, using Mockito 2.0, I had to change all the any() parameters to nullable() in order to stub the real call.
My case was different from the accepted answer. I was trying to mock a package-private method for an instance that did not live in that package
package common;
public class Animal {
void packageProtected();
}
package instances;
class Dog extends Animal { }
and the test classes
package common;
public abstract class AnimalTest<T extends Animal> {
#Before
setup(){
doNothing().when(getInstance()).packageProtected();
}
abstract T getInstance();
}
package instances;
class DogTest extends AnimalTest<Dog> {
Dog getInstance(){
return spy(new Dog());
}
#Test
public void myTest(){}
}
The compilation is correct, but when it tries to setup the test, it invokes the real method instead.
Declaring the method protected or public fixes the issue, tho it's not a clean solution.
The answer by Tomasz Nurkiewicz appears not to tell the whole story!
NB Mockito version: 1.10.19.
I am very much a Mockito newb, so can't explain the following behaviour: if there's an expert out there who can improve this answer, please feel free.
The method in question here, getContentStringValue, is NOT final and NOT static.
This line does call the original method getContentStringValue:
doReturn( "dummy" ).when( im ).getContentStringValue( anyInt(), isA( ScoreDoc.class ));
This line does not call the original method getContentStringValue:
doReturn( "dummy" ).when( im ).getContentStringValue( anyInt(), any( ScoreDoc.class ));
For reasons which I can't answer, using isA() causes the intended (?) "do not call method" behaviour of doReturn to fail.
Let's look at the method signatures involved here: they are both static methods of Matchers. Both are said by the Javadoc to return null, which is a little difficult to get your head around in itself. Presumably the Class object passed as the parameter is examined but the result either never calculated or discarded. Given that null can stand for any class and that you are hoping for the mocked method not to be called, couldn't the signatures of isA( ... ) and any( ... ) just return null rather than a generic parameter* <T>?
Anyway:
public static <T> T isA(java.lang.Class<T> clazz)
public static <T> T any(java.lang.Class<T> clazz)
The API documentation does not give any clue about this. It also seems to say the need for such "do not call method" behaviour is "very rare". Personally I use this technique all the time: typically I find that mocking involves a few lines which "set the scene" ... followed by calling a method which then "plays out" the scene in the mock context which you have staged... and while you are setting up the scenery and the props the last thing you want is for the actors to enter stage left and start acting their hearts out...
But this is way beyond my pay grade... I invite explanations from any passing Mockito high priests...
* is "generic parameter" the right term?
One more possible scenario which may causing issues with spies is when you're testing spring beans (with spring test framework) or some other framework that is proxing your objects during test.
Example
#Autowired
private MonitoringDocumentsRepository repository
void test(){
repository = Mockito.spy(repository)
Mockito.doReturn(docs1, docs2)
.when(repository).findMonitoringDocuments(Mockito.nullable(MonitoringDocumentSearchRequest.class));
}
In above code both Spring and Mockito will try to proxy your MonitoringDocumentsRepository object, but Spring will be first, which will cause real call of findMonitoringDocuments method. If we debug our code just after putting a spy on repository object it will look like this inside debugger:
repository = MonitoringDocumentsRepository$$EnhancerBySpringCGLIB$$MockitoMock$
#SpyBean to the rescue
If instead #Autowired annotation we use #SpyBean annotation, we will solve above problem, the SpyBean annotation will also inject repository object but it will be firstly proxied by Mockito and will look like this inside debugger
repository = MonitoringDocumentsRepository$$MockitoMock$$EnhancerBySpringCGLIB$
and here is the code:
#SpyBean
private MonitoringDocumentsRepository repository
void test(){
Mockito.doReturn(docs1, docs2)
.when(repository).findMonitoringDocuments(Mockito.nullable(MonitoringDocumentSearchRequest.class));
}
Important gotcha on spying real objects
When stubbing a method using spies , please use doReturn() family of methods.
when(Object) would result in calling the actual method that can throw exceptions.
List spy = spy(new LinkedList());
//Incorrect , spy.get() will throw IndexOutOfBoundsException
when(spy.get(0)).thenReturn("foo");
//You have to use doReturn() for stubbing
doReturn("foo").when(spy).get(0);
I've found yet another reason for spy to call the original method.
Someone had the idea to mock a final class, and found about MockMaker:
As this works differently to our current mechanism and this one has different limitations and as we want to gather experience and user feedback, this feature had to be explicitly activated to be available ; it can be done via the mockito extension mechanism by creating the file src/test/resources/mockito-extensions/org.mockito.plugins.MockMaker containing a single line: mock-maker-inline
Source: https://github.com/mockito/mockito/wiki/What%27s-new-in-Mockito-2#mock-the-unmockable-opt-in-mocking-of-final-classesmethods
After I merged and brought that file to my machine, my tests failed.
I just had to remove the line (or the file), and spy() worked.
One way to make sure a method from a class is not called is to override the method with a dummy.
WebFormCreatorActivity activity = spy(new WebFormCreatorActivity(clientFactory) {//spy(new WebFormCreatorActivity(clientFactory));
#Override
public void select(TreeItem i) {
log.debug("SELECT");
};
});
As mentioned in some of the comments, my method was "static" (though being called on by an instance of the class)
public class A {
static void myMethod() {...}
}
A instance = spy(new A());
verify(instance).myMethod(); // still calls the original method because it's static
Work around was make an instance method or upgrade Mockito to a newer version with some config: https://stackoverflow.com/a/62860455/32453
Bit late to the party but above solutions did not work for me , so sharing my 0.02$
Mokcito version: 1.10.19
MyClass.java
private int handleAction(List<String> argList, String action)
Test.java
MyClass spy = PowerMockito.spy(new MyClass());
Following did NOT work for me (actual method was being called):
1.
doReturn(0).when(spy , "handleAction", ListUtils.EMPTY_LIST, new String());
2.
doReturn(0).when(spy , "handleAction", any(), anyString());
3.
doReturn(0).when(spy , "handleAction", null, null);
Following WORKED:
doReturn(0).when(spy , "handleAction", any(List.class), anyString());

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