How to use ReadStreamAndDeserializeIt method of org.mockitousage.serialization.AcrossClassLoaderSerializationTest class

As a follow up, the Mockito public API now has this method:

MockingDetails org.mockito.Mockito.mockingDetails(Object toInspect)

Which is the result of the issue that @David Wallace raised. The returned object supports the methods isMock() as well as isSpy() along with a few other methods that provide additional mocking information.

You can mock without usage of the PowerMock it but in a slightly more complicated way:

KeyStoreSpi keyStoreSpiMock = mock(KeyStoreSpi.class);
KeyStore keyStoreMock = new KeyStore(keyStoreSpiMock, null, "test"){ };
keyStoreMock.load(null);  // this is important to put the internal state "initialized" to true

From now you just mock keyStoreSpiMock, for example:

when(keyStoreSpiMock.engineGetKey(any(), any())).thenReturn(mock(Key.class);

PowerMock implements its own MockMaker which leads to incompatibility with Mockito mock-maker-inline, even if PowerMock is just added as a dependency and not used. If two org.mockito.plugins.MockMaker exist in path then any only one can be used, which one is undetermined.

PowerMock can however delegate calls to another MockMaker, and for then tests are run without PowerMock. Since PowerMock 1.7.0 this can be configured with using the PowerMock Configuration.

The MockMaker can be configured by creating the file org/powermock/extensions/configuration.properties and setting:

mockito.mock-maker-class=mock-maker-inline

Example of using Mockito mock-maker-inline with PowerMock: https://github.com/powermock/powermock-examples-maven/tree/master/mockito2

There are a couple of things you could do to improve your code:

1. Switch to slf4j. This will allow you to code to an interface and be agnostic of the logging implementation under the covers (apache log4j in your case).

2. Switching to slf4j will allow you to not have to concatenate strings when passing to the logging framework - example:

   • this statement: LOGGER.debug("The list already has {} entries" + list.size());
   • can be written like this: LOGGER.debug("The list already has {} entries", list.size());

This has the added benefit of making the place holder in the string literal actually work.

3. You are attempting to assert and capture calls to an object indirectly via the the Logging framework. This will be fragile and error prone as you never know what calls will be made internally in the Logging framework. Mock only your direct dependencies.

4. Don't test logging statements. It's not exactly visible behavior of the class and it makes the test fragile and complicated. Plus, treating the logging statements as you would say using an ArrayList (i.e. part of the language) allows them to be fully exercised AND they output info to the console that may be helpful in debugging a failing test. An example of being fragile is, if you change the logging statement to add more info or maybe you add another logging statement to the method, this test could break for no good reason. At the very least don't assert the number of times called as this will be extremely fragile.

All of that said, if you must test the interactions with the Logging framework - here is a modified version of your code that runs and provides the same functionality. This is basically option #3 from the list of improvements -

package com.spring.mockito;

import static org.mockito.Mockito.spy;
import static org.mockito.Mockito.times;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;

import org.apache.log4j.Logger;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.mockito.runners.MockitoJUnitRunner;

import java.util.Arrays;
import java.util.List;

@RunWith(MockitoJUnitRunner.class)
public class AppTest {

    // create a mock of the logger
    @Mock
    private Logger logger;

    private App uut;

    // Not needed - dont test something that gets called through something else
    // @Captor
    // private ArgumentCaptor<LoggingEvent> captorLoggingEvent;

    @Before
    public void setup() {
        // spy the class under test so we can override the logger method to return our mock logger
        uut = spy(new App());
        when(uut.logger()).thenReturn(logger);

        // Not needed test with the mock directly.
        // Logger root = Logger.getRootLogger();
        // root.addAppender(mockAppender);
        // root.setLevel(Level.DEBUG);
    }

    /**
     * I want to test with over 3 elements.
     */
    @Test
    public void testWithOver3Element() {
        List<String> myList = Arrays.asList("value 1", "value 2", "value 3", "value 4");

        List<String> outputList = uut.addToListIfSizeIsUnder3(myList, "some value");

        Assert.assertEquals(4, outputList.size());
        Assert.assertFalse(myList.contains("some value"));
        verify(logger, times(1)).debug("The list already has {} entries4");

        // not needed
        // try {
        // verify(mockAppender, times(1)).doAppend(captorLoggingEvent.capture());
        // } catch (AssertionError e) {
        // e.printStackTrace();
        // }
        //
        // LoggingEvent loggingEvent = captorLoggingEvent.getAllValues().get(0);
        // Assert.assertEquals("The list already has {} entries", loggingEvent.getMessage());
        // Assert.assertEquals(Level.DEBUG, loggingEvent.getLevel());
    }

    public static class App {
        private static final Logger LOGGER = Logger.getLogger(App.class);

        public List<String> addToListIfSizeIsUnder3(final List<String> list, final String value) {
            if (list == null) {
                logger().error("A null list was passed in");
                return null;
            }
            if (list.size() < 3) {
                list.add(value);
            } else {
                // if you use slf4j this concatenation is not needed
                logger().debug("The list already has {} entries" + list.size());
            }
            return list;
        }

        // make a package private method for testing purposes to allow you to inject a mock
        Logger logger() {
            return LOGGER;
        }
    }
}

You can also look at packages like PowerMockito for mocking statics - but only if absolutely needed.

Hope this helps.

When involving Spring:

If you want to use Spring test framework features in your tests like for example @MockBean, then you have to use @ExtendWith(SpringExtension.class). It replaces the deprecated JUnit4 @RunWith(SpringJUnit4ClassRunner.class)

When NOT involving Spring:

If you just want to involve Mockito and don't have to involve Spring, for example, when you just want to use the @Mock / @InjectMocks annotations, then you want to use @ExtendWith(MockitoExtension.class), as it doesn't load in a bunch of unneeded Spring stuff. It replaces the deprecated JUnit4 @RunWith(MockitoJUnitRunner.class).

To answer your question:

Yes you can just use @ExtendWith(SpringExtension.class), but if you're not involving Spring test framework features in your tests, then you probably want to just use @ExtendWith(MockitoExtension.class).

The Mockito documentation repeatedly says it is often redundant. This appears verbatim both in verify(T)'s Javadoc as multiple single-line comments in the code block in Mockito's main class Javadoc section 2:

Although it is possible to verify a stubbed invocation, usually it's just redundant. If your code cares what get(0) returns, then something else breaks (often even before verify() gets executed). If your code doesn't care what get(0) returns, then it should not be stubbed. Not convinced? See here.

Note that the originally linked article, "Asking and Telling", was written by Mockito originator Szczepan Faber and can be considered an authoritative document in Mockito's design. To excerpt from that post:

Do I really have to repeat the same expression? After all, stubbed interactions are verified implicitly. The execution flow of my own code does it completely for free. Aaron Jensen also noticed that:

If you’re verifying you don’t need to stub unless of course that method returns something that is critical to the flow of your test (or code), in which case you don’t really need to verify, because the flow would have verified.

Just to recap: there is no repeated code.

But what if an interesting interaction shares the characteristic of both asking and telling? Do I have to repeat interactions in stub() and verify()? Will I end up with duplicated code? Not really. In practice: If I stub then it is verified for free, so I don’t verify. If I verify then I don’t care about the return value, so I don’t stub. Either way, I don’t repeat myself. In theory though, I can imagine a rare case where I do verify a stubbed interaction, for example to make sure the stubbed interaction happened exactly n times. But this is a different aspect of behavior and apparently an interesting one. Therefore I want to be explicit and I am perfectly happy to sacrifice one extra line of code…

Recent versions of Mockito (released since this Q&A was posted) have added some additional features that allow or default to stricter mocking styles. Despite this, the prevailing expectation is to avoid brittleness by only verifying what you can't confirm through assertions or successful test completion.

Overall, Mockito's design is to allow tests to be as flexible as possible, coding not to the implementation but instead to the spec of the method you're testing. Though you'll occasionally see a method call as part of a function's spec ("Submits an RPC to the server" or "Calls the passed LoginCallback immediately"), it's much more likely that you'll want to validate the postconditions that you can infer from the stubs: Checking that getFoo was called isn't really a part of the spec as long as you stubbed getFoo to return "foo" and the data store contains a single object with its corresponding property set to "foo".

In short, it is considered good Mockito style to explicitly verify only the interactions that can't be implied from well-crafted stubs and postcondition assertions. They may be good calls for otherwise-unmeasurable side effects—logging code, thread executors, ArgumentCaptors, multiple method calls, callback functions—but generally should not be applied to stubbed interactions.

From what I read on "Issue 53" of mockito (https://code.google.com/p/mockito/issues/detail?id=53) , my code was experiencing a problem due to the validation framework involved in Mockito. Precisely the following code was causing the exception per se.

private ConstantNode getConstantNode(NumericalValue value){
    ConstantNode node = Mockito.mock(ConstantNode.class);
    Mockito.when(node.evaluate()).thenReturn(value);
    Mockito.when(node.toString()).thenReturn(value.toString());
    return node;
}

If you remember from my code, the parameter value is ALSO A MOCK, so that when value.toString() is called on the thenReturn(), I believe (and someone please correct me if I am wrong) that the validation framework is triggered and makes sure that every "when" has had its thenReturn() called/validated/etc. So that if this happenes, the Mockito.when(node.toString()).thenReturn(value.toString() will not be validated because it hasn´t returned from the valute.toString(), which started the whole "validate everything" chain.

How I fixed it:

private ConstantNode getConstantNode(NumericalValue value){
    ConstantNode node = Mockito.mock(ConstantNode.class);
    Mockito.when(node.evaluate()).thenReturn(value);

    String numberToString = value.toString();

    Mockito.when(node.toString()).thenReturn(numberToString);
    return node;
}

This way, it can be validated. I find this a complete code smell because I will literally have to leave a comment that explains why I am using a seemingly useless intermediate variable in the code.

Thanks for the help.

Let's first separate interfaces from classes.

Interfaces are great for mocking (thus allowing for testing your app without the need for the sluggish GWTTestCase):

• IsWidget: when all you need is a handle on a widget, without depending on the Widget class. This is typically used with MVP as a way to represent the view.
• AcceptsOneWidget: when you need a placeholder for a single widget (in the form of an IsWidget). This is typically used with Activities, to insert the view (IsWidget) into the given slot (AcceptsOneWidget).

The classes you list all extend Widget, so they rely on JSNI and (most of the time) need to run in a GWT environment (for unit tests, that means a GWTTestCase):

• Widget: the base of all widgets. Implements IsWidget returning itself from asWidget().
• Composite: a base class when you need to create a widget built from other widgets while hiding their implementation. While you could extend an existing widget, it's generally better to hide it inside a Composite so you only expose the API you need/want to expose. Composite is about "composition rather than inheritance" and encapsulation. Examples of composites in standard widgets include TabPanel (built from a TabBar and DeckPanel), DateBox (built from a TextBox and DatePicker in a PopupPanel), ValueListBox that wraps a ListBox or ValuePicker that wraps a CellList. In many cases, given that panels accept IsWidget children, you could simply implement IsWidget rather extend Composite, but it's sometimes useful to have a true Widget.
• SimplePanel a panel that implements AcceptsOneWidget, useful as a slot when using activities (but you could also easily implement AcceptsOneWidget to insert into any kind of panel)

That being said, Google recently open-sourced GWT-Mockito that plugs Mockito into GWT.create() and uses classloader magic to rewrite JSNI methods and remove final modifiers so you can directly use widgets in tests without the need for GWTTestCase or MVP.

So, all in all, it depends how you approach your code, how you architecture your app. If you use MVP, stick to depending on interfaces only (IsWidget, AcceptsOneWidget) in your presenter so you can easily mock your view in your tests.
Otherwise, or if you want a "simplified MVP" where the view is a UiBinder template, try GWT-Mockito for your tests and directly use widgets.
Of course, you can mix both approaches in the same application. And in any case, build your own widgets as Widgets for low-level things (rarely needed), and Composites or IsWidgets for everything else, rather than extending existing widgets.

You should use RuntimeException or subclass it. Your method has to declare checked exception (example: findByState(String state) throws IOException;) otherwise use RuntimeException:

 when(userRepository.findByState("Karnataka"))
       .thenThrow(new RuntimeException("Exception"));