How to use should_allow_stubbing_and_verifying_compare_to method of org.mockitousage.bugs.CovariantOverrideTest class

It looks like Gradle is not doing it's job. Manually adding the jars may fixed the problem. How to Download and Install jar go here .

and for download mockito use this link

https://mvnrepository.com/artifact/org.mockito/mockito-core/1.10.19

PowerMockRunner is part of powermock-module-junit4.jar. You need to explicity import this jar

You could specify the dependency for this jar as per your requirement. Refer to this link.

This would be hard to test because it loops. One solution would be to break out this.client.newCall(request).execute() into a separate function sendRequest(Request request, int attemptsRemaining). Then you could use a spy that stubs that method to return different responses depending on the number of attempts remaining.
The nice thing I realized about okhttp is that you can just build a fake response yourself. For example,

Request mockRequest = new Request.Builder()
                .url("https://some-url.com")
                .build();
return new Response.Builder()
                .request(mockRequest)
                .protocol(Protocol.HTTP_2)
                .code(401) // status code
                .message("")
                .body(ResponseBody.create(
                        MediaType.get("application/json; charset=utf-8"),
                        "{}"
                ))
                .build();

So you can create and stub a simple method that returns a response, and you're basically good to go for testing.

The MockitoExtension class implements the BeforeEachCallback but not the BeforeAllCallback from JUnit-Jupiter-API. It does therefore not provide any additional behaviour for @BeforeAll annotated methods.

Source extract of MockitoExtension

public class MockitoExtension implements BeforeEachCallback, AfterEachCallback, ParameterResolver {

I think you might need to do a little bit of refactoring. You can create mocks of static methods by creating a MockedStatic variable at class level and use that in your tests and also sometimes it needs to be closed in the @After block, something like

MockedStatic<StaticClass> mockedStaticClass;
@Before
public void setUp()
{
  mockedStaticClass = Mockito.mockStatic(StaticClass.class);
}

@After
public void tearDown() throws Exception
{
  mockedStaticClass.close();
}

@Test
public void yourTest()
{
  //make use of mockedStatic variable you created earlier
}

You're supposed to be creating a mock of the Query interface like this...

@Test
public void test() { 

    Query query = mock(Query.class);

    when(entityManager.createNamedQuery(queryName)).thenReturn(query);

    ...

Maybe you forgot the double quotes around the String literal "queryName". From your code I cannot see where the variable queryName is defined on the last line above.

Try Adding @Spy to your InjectMocks and use the object to "expect" them in a slightly different syntax.

import org.mockito.Spy;

 @InjectMocks
 @Spy
 private MyService myService; 

And now mock the service call

 Mockito.doReturn(mockedSomeObject).when(myService).methodB();

Also change the other mock call to this

Mockito.doReturn(stuff).when(serviceA).method();
Mockito.doReturn(otherStuff).when(serviceB).method();

You need create real A class because you want to test it but you need to mock other classes used in A class. Also, you can find mockito documentation says that don't mock everything.

class ATest {
        @Mock
        private B b;
        private A a;
        @Before
        public void init() {
            MockitoAnnotations.initMocks(this);
            a = new A(b);
        }
        @Test
        public String someMethodTest() {
            String result = "result";
            Mockito.when(b.execute()).thenReturn(result);
            String response = a.someMethod();
            Mockito.verify(b,  Mockito.atLeastOnce()).execute();
            assertEquals(response, result);
        }
    }

I had the same error but for me it was caused by the fact that I had ommited the ID as URL parameter. I ommited it because the ID was present in the JSON body.

When I changed .../restaurant to ...restaurant/1, the error went away.