How to use test_new_instance method of org.mockito.internal.util.reflection.MemberAccessorTest class

After a lot more hunting around and looking at all the options Mockito/Powermock had to offer, I found the solution (which I will share in case others run into this same issue).

When you have private member variables that are never initialized (and just assumed created in other places), you can use the @InjectMocks annotation to "inject" Mocks you want into your class you are testing.

1. Add a variable in your test class for the class you are testing, and give it the annotation @InjectMocks (org.Mockito.InjectMocks).
2. Use @Mock annotations to setup the mocks you want to inject. Use the @Mock (name = "privateVariableNameHere") name property to map the Mock object to the private variable inside your class you are testing.
3. In either a setup function or before you call your class, initialize the mocks. The easiest way I have found is to use a "setup" method with the @Before annotation. Then inside there call MockitoAnnotations.initMocks(this); to quickly initialize anything with the @Mock annotation.
4. Define your Mock functionality in your test method (before calling the method you are testing).
5. Using the @InjectMock object, call your method you are testing... the mocks SHOULD be hooked in and working as defined in the earlier steps.

So for the example class I use above, the code to test/mock would have Connection returned as a mock which you can do whatever with. Based on the example above in my question, this is what the code would look like:

@RunWith(PowerMockRunner.class)
@PrepareForTest({/* Static Classes I am Mocking */})
public class ExampleTest {
  @Mock (name = "queueFactory") //same name as private var.
  QueueConnectionFactory queueFactoryMock;
  @Mock
  Connection connectionMock; //the object we want returned
  @InjectMocks
  Example exampleTester; //the class to test

  @Before
  public void setup(){
    MockitoAnnotations.initMocks(this); // initialize all the @Mock objects
    // Setup other Static Mocks
  }

  @Test
  public void testTestMe(){
    //Mock your objects like other "normally" mocked objects
    PowerMockito.when(queueFactoryMock.createConnection()).thenReturn(connectionMock);
    //...Mock ConnectionMock functionality...
    exampleTester.testMe();
  }
}

See Update below: You don't need a Factory

If you are using Jersey 2, one solution would be to use Custom Injection and Lifecycle Management feature (with HK2 - which comes with the Jersey dist). Also required would be a Mocking framework of course. I'm going to use Mockito.

First create a Factory with mocked instance:

public static interface GreetingService {
    public String getGreeting(String name);
}

public static class MockGreetingServiceFactory 
                                     implements Factory<GreetingService> {
    @Override
    public GreetingService provide() {
        final GreetingService mockedService
                = Mockito.mock(GreetingService.class);
        Mockito.when(mockedService.getGreeting(Mockito.anyString()))
                .thenAnswer(new Answer<String>() {
                    @Override
                    public String answer(InvocationOnMock invocation) 
                                                      throws Throwable {
                        String name = (String)invocation.getArguments()[0];
                        return "Hello " + name;
                    }

                });
        return mockedService;
    }

    @Override
    public void dispose(GreetingService t) {}
}

Then use the AbstractBinder to bind the factory to the interface/service class, and register the binder. (It's all described in the link above):

@Override
public Application configure() {
    AbstractBinder binder = new AbstractBinder() {
        @Override
        protected void configure() {
            bindFactory(MockGreetingServiceFactory.class)
                               .to(GreetingService.class);
        }
    };
    ResourceConfig config = new ResourceConfig(GreetingResource.class);
    config.register(binder);
    return config;
}

Seems like a lot, but it's just an option. I'm not too familiar with the test framework, or if it has an mocking capabilities for injection.

Here is the full test:

import javax.inject.Inject;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.client.Client;
import javax.ws.rs.client.ClientBuilder;
import javax.ws.rs.core.Application;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import org.glassfish.hk2.api.Factory;
import org.glassfish.hk2.utilities.binding.AbstractBinder;
import org.glassfish.jersey.server.ResourceConfig;
import org.glassfish.jersey.test.JerseyTest;
import org.junit.Assert;
import org.junit.Test;
import org.mockito.Mockito;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;

public class ServiceMockingTest extends JerseyTest {

    @Path("/greeting")
    public static class GreetingResource {

        @Inject
        private GreetingService greetingService;

        @GET
        @Produces(MediaType.TEXT_PLAIN)
        public String getGreeting(@QueryParam("name") String name) {
            return greetingService.getGreeting(name);
        }
    }

    public static interface GreetingService {
        public String getGreeting(String name);
    }
    
    public static class MockGreetingServiceFactory 
                                  implements Factory<GreetingService> {
        @Override
        public GreetingService provide() {
            final GreetingService mockedService
                    = Mockito.mock(GreetingService.class);
            Mockito.when(mockedService.getGreeting(Mockito.anyString()))
                    .thenAnswer(new Answer<String>() {
                        @Override
                        public String answer(InvocationOnMock invocation) 
                                                       throws Throwable {
                            String name = (String)invocation.getArguments()[0];
                            return "Hello " + name;
                        }

                    });
            return mockedService;
        }

        @Override
        public void dispose(GreetingService t) {}
    }

    @Override
    public Application configure() {
        AbstractBinder binder = new AbstractBinder() {
            @Override
            protected void configure() {
                bindFactory(MockGreetingServiceFactory.class)
                        .to(GreetingService.class);
            }
        };
        ResourceConfig config = new ResourceConfig(GreetingResource.class);
        config.register(binder);
        return config;
    }
    
    @Test
    public void testMockedGreetingService() {
        Client client = ClientBuilder.newClient();
        Response response = client.target("http://localhost:9998/greeting")
                .queryParam("name", "peeskillet")
                .request(MediaType.TEXT_PLAIN).get();
        Assert.assertEquals(200, response.getStatus());
        
        String msg = response.readEntity(String.class);
        Assert.assertEquals("Hello peeskillet", msg);
        System.out.println("Message: " + msg);
        
        response.close();
        client.close();
       
    }
}

Dependencies for this test:

<dependency>
    <groupId>org.glassfish.jersey.test-framework.providers</groupId>
    <artifactId>jersey-test-framework-provider-grizzly2</artifactId>
    <version>2.13</version>
</dependency>
<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-all</artifactId>
    <version>1.9.0</version>
</dependency>

UPDATE

So in most cases, you really don't need a Factory. You can simply bind the mock instance with its contract:

@Mock
private Service service;

@Override
public ResourceConfig configure() {
    MockitoAnnotations.initMocks(this);
    return new ResourceConfig()
        .register(MyResource.class)
        .register(new AbstractBinder() {
            @Override
            protected configure() {
                bind(service).to(Service.class);
            }
        });
}

@Test
public void test() {
    when(service.getSomething()).thenReturn("Something");
    // test
}

Much simpler!

You can try the following idea (taken from similar discussion on github):

.doAnswer { throw ServiceException("Bad Request") }

Having such interface:

interface Foo {
    void method(String s);
}

One idea is to use regular expression matching:

final Foo mock = mock(Foo.class);
mock.method("abc");
verify(mock).method(matches(".{3}"));

Unfortunately there is no built-in matcher for string length (there should be!), but it's easy to write custom one:

private static String hasSize(final int size) {
    return argThat(new ArgumentMatcher<String>() {
        @Override
        public boolean matches(Object argument) {
            return argument.toString().length() == size;
        }
    });
}

Now simply call static method:

verify(mock).method(hasSize(4));

You can use the gradle maven plugin. This adds the pom convention method to your project, which you can use in a task to generate a pom.xml file, like

task writeNewPom {
    doLast {
        pom {
            project {
                groupId 'org.example'
                artifactId 'test'
                version '1.0.0'
                inceptionYear '2008'
                licenses {
                    license {
                        name 'The Apache Software License, Version 2.0'
                        url 'http://www.apache.org/licenses/LICENSE-2.0.txt'
                        distribution 'repo'
                    }
                }
            }
        }.writeTo("pom.xml")
    }
}

Then you call gradle createPom to generate the pom.xml in the project root. Of all the things in the pom definition, you should really provide groupId, artifactId and version, other thins like licenses are not that important.

You can also look at this example for a project definition with some dependencies, and try running it to see what it produces.

Some of the new keywords were added and some techniques were deprecated. Please check

Mocking static methods is available since Mockito 3.4.

See pull request: Mockito #1013: Defines and implements API for static mocking.

Please note that the fact that this feature is available is not equivalent with recommendation to use it. It is aimed at legacy apps where you cannot refactor the source code.

Having said that:

Test when static method takes no arguments:

try (MockedStatic<SomePublicClass> dummyStatic = Mockito.mockStatic(SomePublicClass.class)) {
    dummyStatic.when(SomePublicClass::myPublicStaticFunc)
               .thenReturn(5);
    // when
    System.out.println(SomePublicClass.myPublicStaticFunc());
    //then
    dummyStatic.verify(
            times(1),
            SomePublicClass::myPublicStaticFunc
    );
}

Test when static methods takes arguments:

try (MockedStatic<SomePublicClass> dummyStatic = Mockito.mockStatic(SomePublicClass.class)) {
    dummyStatic.when(() -> SomePublicClass.myPublicStaticFunc(anyInt()))
               .thenReturn(5);
    // when
    System.out.println(SomePublicClass.myPublicStaticFunc(7));
    //then
    dummyStatic.verify(
            times(1), 
            () -> SomePublicClass.myPublicStaticFunc(anyInt())
    );
}

The rule S2699 (Tests should include assertions) from the SonarQube Java Analyzer does not perform cross-procedural analysis and only explore body of methods being identified as test method (usually annotated with @Test).

Consequently, if the only assertions which will be called when executing the test method are done by a dedicated method (to avoid duplication), then the rule will raise an issue. This is a known limitation of the rule and we will deal with it only when we will be able to efficiently perform cross-procedural analysis.

Regarding the issues raised by SonarQube on such cases, you can safely mark them as Won't Fix.

Regarding the detected assertions, the rule consider as assertions the usual assert/fail/verify/expect methods from the following (unit test) frameworks :

• JUnit
• Fest (1.x & 2.x)
• AssertJ
• Hamcrest
• Mockito
• Spring
• EasyMock

Try anyInt():

when(candidateService.findById(anyInt())).thenReturn(new Candidate());

For example I have anyLong() in my project:

when(dao.getAddress(anyLong())).thenReturn(Arrays.asList(dto));

EDIT: You must import:

import static org.mockito.Matchers.anyInt;

Not possible through mockito. From their wiki

Why Mockito doesn't mock private methods?

Firstly, we are not dogmatic about mocking private methods. We just don't care about private methods because from the standpoint of testing private methods don't exist. Here are a couple of reasons Mockito doesn't mock private methods:

It requires hacking of classloaders that is never bullet proof and it changes the api (you must use custom test runner, annotate the class, etc.).

It is very easy to work around - just change the visibility of method from private to package-protected (or protected).

It requires me to spend time implementing & maintaining it. And it does not make sense given point #2 and a fact that it is already implemented in different tool (powermock).

Finally... Mocking private methods is a hint that there is something wrong with OO understanding. In OO you want objects (or roles) to collaborate, not methods. Forget about pascal & procedural code. Think in objects.