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How to mock static method in Junit 5? [duplicate]

I want to mock a static method in JUnit 5. But unfortunately, JUnit 5 doesn’t support Mockito. Is there another method to achieve the same other than reverting back to JUnit 4?

From Mockito 3.4.0 (2020-07-10), it is possible to mock static methods out of the box even in JUnit 5, without any extension.
In the documentation, you can find an example: 48. Mocking static methods (since 3.4.0)
Important note: You need to use inline mock maker. So the dependency to use is not the core one:
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-inline</artifactId>
<version>3.4.6</version>
<scope>test</scope>
</dependency>
Example:
Class under test:
package teststatics;
public class FooWithStatics {
public static Long noParameters() {
return System.currentTimeMillis();
}
public static String oneParameter(String param1) {
return param1.toUpperCase();
}
}
Test class:
package teststatics;
import org.junit.jupiter.api.Test;
import org.mockito.MockedStatic;
import static org.junit.jupiter.api.Assertions.*;
import static org.mockito.Mockito.*;
public class FooWithStaticsTest {
#Test
void testStatic() {
// Before mock scope, usual behavior.
assertNotEquals(0L, FooWithStatics.noParameters());
assertNotEquals("yyy", FooWithStatics.oneParameter("xxx"));
// Mock scope
try (MockedStatic mocked = mockStatic(FooWithStatics.class)) {
// Mocking
mocked.when(FooWithStatics::noParameters).thenReturn(0L);
mocked.when(() -> FooWithStatics.oneParameter("xxx")).thenReturn("yyy");
// Mocked behavior
assertEquals(0L, FooWithStatics.noParameters());
assertEquals("yyy", FooWithStatics.oneParameter("xxx"));
// Verifying mocks.
mocked.verify(times(1), FooWithStatics::noParameters);
mocked.verify(times(1), () -> FooWithStatics.oneParameter("xxx"));
}
// After mock scope returns to usual behavior.
assertNotEquals(0L, FooWithStatics.noParameters());
assertNotEquals("yyy", FooWithStatics.oneParameter("xxx"));
}
}

The short answer is no, as the Mockito team is done with their work and is waiting for the JUnit team for an extension and are discussing here a lot.
With some overhead you can: As JUnit 5 provides support for running legacy JUnit 4, and there you can use Mockito. So you can create tests in Junit4 for these cases:
A sample project for migration setup with gradle and with mvn. From there I am using PowerMock 2.0 beta with Mockito 2.

The reason why Mockito doesn't provide static methods mocking at the moment is because of the common belief that static method shouldn't need to be mocked.
However, there is an open item for Mockito here that discusses the issue.
While this doesn't answer your question, in general it tells you why you shouldn't need the feature at all or will allow you to join the conversation with your ideas.

Make sure to have mockito-inline dependency in your POM file
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-inline</artifactId>
<version>3.6.28</version>
<scope>test</scope>
</dependency>
In my case I had to test scenario where exception thrown static method encode() of URLEncoder Class, so for that
try (MockedStatic theMock = mockStatic(URLEncoder.class)) {
theMock.when(() -> URLEncoder.encode("Test/11", StandardCharsets.UTF_8.toString()))
.thenThrow(UnsupportedEncodingException.class);
when(restClient.retrieveByName("Test%2F11")).thenReturn(null);
Assertions.assertThrows(ResponseStatusException.class, ()->service.retrieveByName("Test/11"));
}

We can mock a static method by JMockit.
JMockit is used for mocking the external dependencies outside the test boundary, similar to Mockito and other such mocking libraries.
The most important feature of JMockit is that it lets us mock anything, even the things that are hard to mock with other libraries such as constructors, static and final methods. It even allows mocking the member fields and initialization blocks as well.
Follow the below steps to enable JMockit:
The JMockit artifact is located in the central Maven repository, add the JMockit dependency in pom.xml
<!-- https://mvnrepository.com/artifact/org.jmockit/jmockit -->
<dependency>
<groupId>org.jmockit</groupId>
<artifactId>jmockit</artifactId>
<version>1.49</version>
<scope>test</scope>
</dependency>
Mock the Class method in TestClass:
public class TestClass{
#Test
public void testMethod() {
new MockUp<ClassName>(){
#Mock
//mock the method here
};
}
}
Follow the tutorial to know more about how to use the JMockit.

How to replace WireMock #Rule annotation in JUnit 5?

I'm using WireMock in my tests and have such a line of code:
#Rule
public WireMockRule wireMockRule = new WireMockRule(8080);
I want to switch to JUnit 5. So I added the next dependency (using Gradle):
testCompile('org.junit.jupiter:junit-jupiter-engine:5.1.1')
But there are no suggestions when I'm trying to import #Rule annotation.
Do I need to add another module of JUnit dependency? Or are rules not supported in JUnit 5? If not, how can I replace #Rule annotation to make tests work again?

In a general way, what you did with #Rule and #ClassRule in JUnit 4 should be done with #ExtendWith and Extension that associated provide a very close feature in JUnit 5.
It works as standards JUnit lifecycle hooks but that it is extracted in a Extension class. And similarly to #Rule, as many Extensions as required may be added for a test class.
To handle the issue you have several possible approaches among :
keep the JUnit 4 way (JUnit 5 owns the JUnit Vintage part that allows to execute JUnit 3 or 4 tests).
rewrite the #Rule as an Extension.
do the actual processing done by WireMockRule (start the server, execute your tests and stop the server) in each test of class with #BeforeEach and #AfterEach hook methods.
use a third library that implements the equivalent of WireMockRule in the JUnit 5 Extension way such as https://github.com/lanwen/wiremock-junit5
Note that your issue already discussed in the JUnit 5 Issues.

JUnit 4 annotations #Rule and #ClassRule do not exist in JUnit 5. Basically there is a new extension model that can be used to implement extensions with the same functionality. These extensions can be used with the #ExtendWith annotation.
There is a limited migration support for a subset of JUnit 4 rules in the junit-jupiter-migrationsupport module. Unfortunately, it's only limited to subclasses of ExternalResource and Verifier.
Before wiremock has official support for JUnit you have some workarounds:
Run JUnit 4 tests side by side with JUnit 5 tests with the junit-vintage-engine.
Start and stop the server yourself in the test code.
Use a 3rd party extension like wiremock-junit5 or wiremock-extension.

There is now official support for JUnit 5 Jupiter from WireMock 2.31.0.
Docs here: http://wiremock.org/docs/junit-jupiter/

The https://github.com/webcompere/java-test-gadgets project lets you solve this in a couple of ways.
You can use its support for JUnit 4 rules via the DangerousRuleAdapter - which will attempt to turn any JUnit 4 rule into a Plugin:
#ExtendWith(PluginExtension.class)
public class DangerousRuleAdapterExampleTest {
#Plugin
private DangerousRuleAdapter<WireMockRule> adapter =
new DangerousRuleAdapter<>(new WireMockRule());
#Test
void theTest() {
// use wiremock rule here
WireMockRule rule = adapter.get();
}
The rule adapters cannot work with rules that inspect the test class or the test method, but make a good attempt at running the rule.
There's also support for running a rule around some code:
TemporaryFolder temporaryFolder = new TemporaryFolder();
// let's use this temp folder with some test code
executeWithRule(temporaryFolder, () -> {
// here, the rule is _active_
callSomethingThatUses(temporaryFolder.getRoot());
});
And you can easily create your own new JUnit 5 plugin by using the PluginExtension and TestResource.of
#ExtendWith(PluginExtension.class)
class TestResourceIsActiveDuringTest {
private WireMockServer server;
#Plugin
private TestResource someResource = TestResource.from(() -> server.start(),
() -> server.stop());

From the JUnit 5 user guide:
#Rule and #ClassRule no longer exist; superseded by #ExtendWith and #RegisterExtension. See also "Limited JUnit 4 Rule Support".
However, as pointed out by Tom, WireMock has full JUnit Jupiter support since version 2.31.0:
// New JUnit 5 extension
#WireMockTest
class DeclarativeWireMockTest {
#Test
void test_something_with_wiremock(WireMockRuntimeInfo wmRuntimeInfo) {
// The static DSL will be automatically configured for you
stubFor(get("/static-dsl").willReturn(ok()));
// Instance DSL can be obtained from the runtime info parameter
WireMock wireMock = wmRuntimeInfo.getWireMock();
wireMock.register(get("/instance-dsl").willReturn(ok()));
// Info such as port numbers is also available
int port = wmRuntimeInfo.getHttpPort();
// Do some testing...
}
}
For more information, please refer to the corresponding docs.

How to use Mockito with JUnit5

How can I use injection with Mockito and JUnit 5?
In JUnit4 I can just use the #RunWith(MockitoJUnitRunner.class) Annotation. In JUnit5 is no #RunWith Annotation?

There are different ways to use Mockito - I'll go through them one by one.
Manually
Creating mocks manually with Mockito::mock works regardless of the JUnit version (or test framework for that matter).
Annotation Based
Using the #Mock-annotation and the corresponding call to MockitoAnnotations::initMocks
to create mocks works regardless of the JUnit version (or test framework for that matter but Java 9 could interfere here, depending on whether the test code ends up in a module or not).
Mockito Extension
JUnit 5 has a powerful extension model and Mockito recently published one under the group / artifact ID org.mockito : mockito-junit-jupiter.
You can apply the extension by adding #ExtendWith(MockitoExtension.class) to the test class and annotating mocked fields with #Mock. From MockitoExtension's JavaDoc:
#ExtendWith(MockitoExtension.class)
public class ExampleTest {
#Mock
private List list;
#Test
public void shouldDoSomething() {
list.add(100);
}
}
The MockitoExtension documentation describes other ways to instantiate mocks, for example with constructor injection (if you rpefer final fields in test classes).
No Rules, No Runners
JUnit 4 rules and runners don't work in JUnit 5, so the MockitoRule and the Mockito runner can not be used.

Use Mockito's MockitoExtension. The extension is contained in a new artifact mockito-junit-jupiter:
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-junit-jupiter</artifactId>
<version>4.5.1</version>
<scope>test</scope>
</dependency>
It allows you to write tests as you would have with JUnit 4:
import org.mockito.junit.jupiter.MockitoExtension;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
#ExtendWith(MockitoExtension.class)
class MyTest {
#Mock
private Foo foo;
#InjectMocks
private Bar bar; // constructor injection
...
}

There are different ways to do but the cleaner way and that also respects the JUnit 5 philosophy is creating a org.junit.jupiter.api.extension.Extension for Mockito.
1) Creating mocks manually makes lose the benefit of additional Mockito checks to ensure you use correctly the framework.
2) Calling MockitoAnnotations.initMocks(this) in every test classes is boiler plate code that we could avoid.
And making this setup in an abstract class is not a good solution either.
It couples every test classes to a base class.
If then you need a new base test class for good reasons, you finish with a 3- level class hierarchy. Please avoid that.
3) Test Rules is a JUnit 4 specificity.
Don't even think of that.
And the documentation is clear about that :
However, if you intend to develop a new extension for JUnit 5 please
use the new extension model of JUnit Jupiter instead of the rule-based
model of JUnit 4.
4) Test Runner is really not the way to extend the JUnit 5 framework.
JUnit 5 simplified the hell of the Runners of JUnit 4 by providing an extension model for writing tests thanks to JUnit 5 Extensions.
Don't even think of that.
So favor the org.junit.jupiter.api.extension.Extension way.
EDIT : Actually, Mockito bundles a jupiter extension : mockito-junit-jupiter
Then, very simple to use :
import org.mockito.junit.jupiter.MockitoExtension;
#ExtendWith(MockitoExtension.class)
public class FooTest {
...
}
Here is an addition to the excellent answer of Jonathan.
By adding as dependency the mockito-junit-jupiter artifact, the use of #ExtendWith(MockitoExtension.class) produced the following exception as the test is executed :
java.lang.NoSuchMethodError:
org.junit.platform.commons.support.AnnotationSupport.findAnnotation(Ljava/util/Optional;Ljava/lang/Class;)Ljava/util/Optional;
THe problem is that mockito-junit-jupiter depends on two independent libraries.
For example for mockito-junit-jupiter:2.19.0 :
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-core</artifactId>
<version>2.19.0</version>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-api</artifactId>
<version>5.1.0</version>
<scope>runtime</scope>
</dependency>
The problem was I used junit-jupiter-api:5.0.1.
So as junit-jupiter-api moves still often in terms of API, make sure you depend on the same version of junit-jupiter-api that mockito-junit-jupiter depends on.

You have to use the new #ExtendWith annotation.
Unfortunately there is no extension released yet.
On github you can see a beta implementation for the extension. as a example demo test.

code-coverage of the getter through the assert

While unit-testing, is there a way to enable code-coverage analysis only during some steps?
I wish to measure the code-coverage of the assert part of a test.
The tools that I currently use don't make the difference if the line is executed during the Action-part of the test, or during the assert-part.
Accordingly, I cannot check if all the getter of my beans are read by the assert method.
Ideally I want to activate the covering measure only during the execution of some of my methods.
A sample of code:
//method to test
void runToTest(Bean myBean){
myBean.setA(1);
myBean.setB(2);
aString=myBean.getA()+myBean.getB();
}
#Test
void should_check_all_field(){
myBean=new Bean()
myService.runToTest(myBean);
assertMethode();
}
void assertMethod(){
Assert.assertNotNull(myBean.getA())
}
Currently, the tools I use report than getA and getB are covered. I want a way to detect that getB hasn't been read by the assertMethod.
I use Java and IntelliJ and my test class follows the Arrange-Act-Assert syntax.

No, I am not aware of any tool that supports this functionality.
The code coverage expresses which portion of your source code was run through by the tests. By checking the result of a get method you are testing also the correctness of the getter. Thus, a test checks more than what is directly covered by assertion statements.
What you are probably looking for is mutation testing. You want to see if the code is not just executed by the test but as well if the test is capable of detecting an incorrect behaviour of the code. Mutation testing introduces faults into the source code and analyzes whether the tests can reveal these.
See also: https://stackoverflow.com/a/27400613/584532

Correct me if I misunderstood something, you are doing JUnit test and then you are checking coverage as part of the test? It seems like manual step to me, which is something you do not want in JUnit testing, right?
In the following example I used EasyMock, but you can use whatever you prefer ;-)
#Test
public void testGetters() {
Bean bean = EasyMock.createMock(Bean.class);
// set your expectations
EasyMock.expect(bean.getA()).andReturn(0).times(1);
EasyMock.replay(bean);
// use the bean
bean.getA(); // if this is commented, test fails
// verify your expectations
EasyMock.verify(bean);
}
Is this similar to what you want to achieve?
I used maven project and my dependencies are
<dependencies>
<dependency>
<groupId>org.easymock</groupId>
<artifactId>easymock</artifactId>
<version>3.3.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
</dependencies>

Grouping JUnit tests

Is there any way to group tests in JUnit, so that I can run only some groups?
Or is it possible to annotate some tests and then globally disable them?
I'm using JUnit 4, I can't use TestNG.
edit: #RunWith and #SuiteClasses works great. But is it possible to annotate like this only some tests in test class? Or do I have to annotate whole test class?

JUnit 4.8 supports grouping:
public interface SlowTests {}
public interface IntegrationTests extends SlowTests {}
public interface PerformanceTests extends SlowTests {}
And then...
public class AccountTest {
#Test
#Category(IntegrationTests.class)
public void thisTestWillTakeSomeTime() {
...
}
#Test
#Category(IntegrationTests.class)
public void thisTestWillTakeEvenLonger() {
...
}
#Test
public void thisOneIsRealFast() {
...
}
}
And lastly,
#RunWith(Categories.class)
#ExcludeCategory(SlowTests.class)
#SuiteClasses( { AccountTest.class, ClientTest.class })
public class UnitTestSuite {}
Taken from here: https://community.oracle.com/blogs/johnsmart/2010/04/25/grouping-tests-using-junit-categories-0
Also, Arquillian itself supports grouping:
https://github.com/weld/core/blob/master/tests-arquillian/src/test/java/org/jboss/weld/tests/Categories.java

Do you want to group tests inside a test class or do you want to group test classes? I am going to assume the latter.
It depends on how you are running your tests. If you run them by Maven, it is possible to specify exactly what tests you want to include. See the Maven surefire documentation for this.
More generally, though, what I do is that I have a tree of test suites. A test suite in JUnit 4 looks something like:
#RunWith(Suite.class)
#SuiteClasses({SomeUnitTest1.class, SomeUnitTest2.class})
public class UnitTestsSuite {
}
So, maybe I have a FunctionTestsSuite and a UnitTestsSuite, and then an AllTestsSuite which includes the other two. If you run them in Eclipse you get a very nice hierarchical view.
The problem with this approach is that it's kind of tedious if you want to slice tests in more than one different way. But it's still possible (you can for example have one set of suites that slice based on module, then another slicing on the type of test).

To handle the globally disabling them, JUnit (4.5+) has two ways One is to use the new method assumeThat. If you put that in the #BeforeClass (or the #Before) of a test class, and if the condition fails, it will ignore the test. In the condition you can put a system property or something else that can be globally set on or off.
The other alternative is to create a custom runner which understands the global property and delegates to the appropriate runner. This approach is a lot more brittle (since the JUnit4 internal runners are unstable and can be changed from release to release), but it has the advantage of being able to be inherited down a class hierarchy and be overridden in a subclass. It is also the only realistic way to do this if you have to support legacy JUnit38 classes.
Here is some code to do the custom Runner. Regarding what getAppropriateRunnerForClass might do, the way I implemented it was to have a separate annotation that tells the custom runner what to run with. The only alternative was some very brittle copy paste from the JUnit code.
private class CustomRunner implements Runner
private Runner runner;
public CustomRunner(Class<?> klass, RunnerBuilder builder) throws Throwable {
if (!isRunCustomTests()) {
runner = new IgnoredClassRunner(klass);
} else {
runner = getAppropriateRunnerForClass(klass, builder);
}
public Description getDescription() {
return runner.getDescription();
}
public void run(RunNotifier notifier) {
runner.run(notifier);
}
}
EDIT: The #RunWith tag only works for a whole class. One way to work around that limiation is to move the test methods into a static inner class and annotate that. That way you have the advantage of the annotation with the organization of the class. But, doing that won't help with any #Before or #BeforeClass tags, you will have to recreate those in the inner class. It can call the outer class's method, but it would have to have its own method as a hook.

In JUnit 5 you can declare #Tag for filtering tests, either at the class or method level; analogous to test groups in TestNG or Categories in JUnit 4
From the javadoc :
tags are used to filter which tests are executed for a given test
plan. For example, a development team may tag tests with values such
as "fast", "slow", "ci-server", etc. and then supply a list of tags to
be used for the current test plan, potentially dependent on the
current environment.
For example you could declare a test class with a "slow" #Tag that will be inherited for all methods and override it for some methods if required :
import org.junit.jupiter.api.Tag;
import org.junit.jupiter.api.Test;
#Tag("slow")
public class FooTest{
//
#Test
void loadManyThings(){
...
}
#Test
void loadManyManyThings(){
...
}
#Test
#Tag("fast")
void loadFewThings(){
...
}
}
You could apply the same logic for other test classes.
In this way test classes (and methods too) belongs to a specific tag.
As a good practice instead of copying and pasting #Tag("fast") and #Tag("slow") throughout the test classes, you can create custom composed annotations.
For example :
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.junit.jupiter.api.Tag;
#Target({ ElementType.TYPE, ElementType.METHOD })
#Retention(RetentionPolicy.RUNTIME)
#Tag("slow")
public #interface Slow {
}
and use it as :
#Test
#Slow
void slowProcessing(){
...
}
To enable or disable test marked with a specific tag during the text execution you can rely on the maven-surefire-plugin documentation :
To include tags or tag expressions, use groups.
To exclude tags or tag expressions, use either excludedGroups.
Just configure in your pom.xml the plugin according to your requirement (example of the doc) :
<build>
<plugins>
...
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.0</version>
<configuration>
<groups>acceptance | !feature-a</groups>
<excludedGroups>integration, regression</excludedGroups>
</configuration>
</plugin>
</plugins>
</build>
For information the test goal documentation is not updated.

Try JUnit Test Groups. From documentation :
#TestGroup("integration")
public class MyIntegrationTest {
#ClassRule
public static TestGroupRule rule = new TestGroupRule();
...
}
Execute a simple test group: -Dtestgroup=integration
Execute multiple test groups: -Dtestgroup=group1,group2
Execute all test groups: -Dtestgroup=all

You can create test Suite objects that contain groups of tests. Alternatively, your IDE (like Eclipse) may have support for running all the tests contained in a given package.

You can Use Test Suite(http://qaautomated.blogspot.in/2016/09/junit-test-suits-and-test-execution.html) or you can Junit Categories(http://qaautomated.blogspot.in/2016/09/junit-categories.html) for grouping your test cases effectively.