Liferay 7 & JUnit : Mock Local Custom Local Service Util - junit

Question

I'm trying to mock with powermockito my custom local service util, but i always get an error.
#RunWith(PowerMockRunner.class)
#PrepareForTest({ServiceSubscriptionLocalServiceUtil.class})
public class CStreamTest {
#Before
public void setUp() throws NoSuchFieldException, IllegalAccessException {
.........
mockStatic(ServiceSubscriptionLocalServiceUtil.class);
.........
}
}
and i'm getting the following error :
java.lang.ExceptionInInitializerError
at sun.reflect.GeneratedSerializationConstructorAccessor4.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at org.objenesis.instantiator.sun.SunReflectionFactoryInstantiator.newInstance(SunReflectionFactoryInstantiator.java:48)
at org.objenesis.ObjenesisBase.newInstance(ObjenesisBase.java:73)
at org.mockito.internal.creation.instance.ObjenesisInstantiator.newInstance(ObjenesisInstantiator.java:19)
at org.mockito.internal.creation.bytebuddy.SubclassByteBuddyMockMaker.createMock(SubclassByteBuddyMockMaker.java:47)
at org.mockito.internal.creation.bytebuddy.ByteBuddyMockMaker.createMock(ByteBuddyMockMaker.java:25)
at org.powermock.api.mockito.mockmaker.PowerMockMaker.createMock(PowerMockMaker.java:41)
at org.mockito.internal.util.MockUtil.createMock(MockUtil.java:35)
at org.mockito.internal.MockitoCore.mock(MockitoCore.java:62)
at org.mockito.Mockito.mock(Mockito.java:1896)
at org.powermock.api.mockito.internal.mockcreation.DefaultMockCreator.createMethodInvocationControl(DefaultMockCreator.java:108)
at org.powermock.api.mockito.internal.mockcreation.DefaultMockCreator.doCreateMock(DefaultMockCreator.java:61)
at org.powermock.api.mockito.internal.mockcreation.DefaultMockCreator.createMock(DefaultMockCreator.java:53)
at org.powermock.api.mockito.internal.mockcreation.DefaultMockCreator.mock(DefaultMockCreator.java:40)
at org.powermock.api.mockito.PowerMockito.mockStatic(PowerMockito.java:62)
at com.e.c.stream.impl.test.CStreamTest.setUp(CStreamTest.java:50)
i add some parts of my pom.xml :
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>3.12.0</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-core</artifactId>
<version>2.24.0</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-all</artifactId>
<version>1.10.19</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-core</artifactId>
<version>2.0.0</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-module-junit4</artifactId>
<version>2.0.0</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-api-mockito2</artifactId>
<version>2.0.0</version>
<scope>test</scope>
</dependency>
Any ideas ?
Thanks

Answer 1

Liferay's *LocalServiceUtil classes contain a bunch of static methods that just simplify the lookup of an actual service implementation. Given that you state you're on Liferay 7, you should just utilize the services themselves and rely on #Reference dependency management and injection in the code that uses them. This way you just need to mock a regular interface that is not loaded with some default implementation and lookup.
Another option is to test the implementation - and write tests for the code "above" the service, as well as its implementation. It's typically hard to write UI-layer code, e.g. portlets, in a test-driven fashion, where mocking isn't heavily dependent on the implementation of the service and the calling classes.

Answer 2

Normally services utility classes created by Service builder do not have a no arg constructor, not even a constructor for that matter.
But if you check the log you will see and this is your issue:
New instance of the class is created inside PowerMock.
java.lang.ExceptionInInitializerError at sun.reflect.GeneratedSerializationConstructorAccessor4.newInstance(Unknown Source)
After trying to create an instance for: ObjenesisBase....
Even though it has not constructors, services utils normally initialize static members, like a ServiceTracker.
You could create a bummy service impl or your code could use the service reference instead of the util, you could mock that guy. Several options here, even mocking methods that give you the service to give you a dummy service.
But in summary, you cannot just do:
mockStatic(ServiceSubscriptionLocalServiceUtil.class);
As this will create an instance, and that instance has static members that need to be initialized.