How to use mockClassConstruction method of org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator class

Mock objects are used just to get values. You can setup what values are returned, just like jou did using:

Mockito.when(permission.getPermissionById(5L)).thenReturn(pemission);

Now when you call permission.getPermissionById(5L) you'll get permission.

Maybe you are talking about capturing parameters passed to the method. You can do it using ArgumentCaptor.

Sample code:

ArgumentCaptor<Person> argument = ArgumentCaptor.forClass(Person.class);
verify(mock).doSomething(argument.capture());
assertEquals("John", argument.getValue().getName());

You are confusing a Mock with a Spy.

In a mock all methods are stubbed and return "smart return types". This means that calling any method on a mocked class will do nothing unless you specify behaviour.

In a spy the original functionality of the class is still there but you can validate method invocations in a spy and also override method behaviour.

What you want is

MyProcessingAgent mockMyAgent = Mockito.spy(MyProcessingAgent.class);

A quick example:

static class TestClass {

    public String getThing() {
        return "Thing";
    }

    public String getOtherThing() {
        return getThing();
    }
}

public static void main(String[] args) {
    final TestClass testClass = Mockito.spy(new TestClass());
    Mockito.when(testClass.getThing()).thenReturn("Some Other thing");
    System.out.println(testClass.getOtherThing());
}

Output is:

Some Other thing

NB: You should really try to mock the dependencies for the class being tested not the class itself.

You can do it with Mockito and PowerMockito.

Say you have ClassUnderTest with a constructor

public class ClassUnderTest {
    String name;
    boolean condition;

    public ClassUnderTest(String name, boolean condition) {
       this.name = name;
       this.condition = condition;
       init();
    }

    ...
}

And another class that calls that constructor

public class MyClass {

    public MyClass() { } 

    public void createCUTInstance() {
       // ...
       ClassUnderTest cut = new ClassUnderTest("abc", true);
       // ...
    }

    ...
}

At the Test class we could...

(1) use PowerMockRunner and cite both target classes above in the PrepareForTest annotation:

@RunWith(PowerMockRunner.class)
@PrepareForTest({ ClassUnderTest.class, MyClass.class })
public class TestClass {

(2) intercept the constructor to return a mock object:

@Before
public void setup() {
    ClassUnderTest cutMock = Mockito.mock(ClassUnderTest.class);
    PowerMockito.whenNew(ClassUnderTest.class)
                .withArguments(Matchers.anyString(), Matchers.anyBoolean())
                .thenReturn(cutMock);
}

(3) validate the constructor call:

@Test
public void testMethod() {
    // prepare
    MyClasss myClass = new MyClass();

    // execute
    myClass.createCUTInstance();

    // checks if the constructor has been called once and with the expected argument values:
    String name = "abc";
    String condition = true;
    PowerMockito.verifyNew(ClassUnderTest.class).withArguments(name, condition);
}

The implementation is the unit that needs to be tested. That is of course what you are instantiating and what contains the program/business logic.

If you had a critical interface and you wanted to make sure every implementation adhered to it properly, then you may write a test suite that focuses on the interface and requires an instance be passed in (agnostic of any implementation type).

Yes, it would probably be easier to use Mockito for PrintStream, it may not always be possible to avoid using a mock object like you did in this specific example.

From the Mockito FAQ:

What are the limitations of Mockito

• Cannot mock final methods - their real behavior is executed without any exception. Mockito cannot warn you about mocking final methods so be vigilant.

Nutshell: Can't always use when to stub spies; use doReturn.

Assuming static imports of spy and doReturn (both PowerMockito):

@RunWith(PowerMockRunner.class)
@PrepareForTest(B.class)
public class BTest {
    @Test public void testClass() throws Exception {
        B b = spy(new B());
        doReturn(42).when(b, "m");
        b.asd();
    }
}

You could also @PrepareForTest(A.class) and set up the doReturn on when(a, "m"). Which makes more sense depends on the actual test.

I think the reason may be that mock object libraries typically create mocks by dynamically creating classes at runtime (using cglib). This means they either implement an interface at runtime (that's what EasyMock does if I'm not mistaken), or they inherit from the class to mock (that's what Mockito does if I'm not mistaken). Both approaches do not work for static members, since you can't override them using inheritance.

The only way to mock statics is to modify a class' byte code at runtime, which I suppose is a little more involved than inheritance.

That's my guess at it, for what it's worth...

UPDATE

There are newer java7 versions that fix this issue. As is written in reply to Powermock / Javassist creates illegal constructors for JDK 1.7.0u65 and 1.8.0u11 with -target 7 #525

upgrading from java 7u71 to 7u75 fixed the problem

Rootcause

Upon investigation I heard cries for help from all over the internet from all tools and languages that built upon JDK.

Turns out the cause is new java bytecode standard that gets checked by new verifier. But unfortunately javassist sometimes is asked by powermock to produce changes into bytecode that are no longer accepted by this new shiny veryfier.

Workaround (for those who cannot go with newer java)

As a workaround in JRebel blog they suggested using -noverify flag upon starting JVM However i found from Java 7 Bytecode Verifier: Huge backward step for the JVM blog post alternative workaround that works on java7: -XX:-UseSplitVerifier

As my tests run in some unaccessible server and are executed as part of maven build, i needed to find a way to pass that argument along with my project files. First workable solution i discovered is to add this parameter to configurtaion of surefire plugin in pom.xml as follows:

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-surefire-plugin</artifactId>
            <version>2.10</version>
            <configuration>
                <argLine>-XX:-UseSplitVerifier</argLine>
            </configuration>
        </plugin>
        <plugin>
    </plugins>
</build>

I suppose that on java8 one could use similar method to call tests with -noverify key, but haven't had the chance to confirm that.

Other related resources to keep eye on

Powermock / Javassist creates illegal constructors for JDK 1.7.0u65 and 1.8.0u11 with -target 7. Powermock / Javassist creates illegal constructors for JDK 1.7.0u65 and 1.8.0u11 with -target 7 #525

Spring provides a class called MockHttpServletRequest, which can be used to test code that needs a HttpServletRequest.

public void testCheckBatchExecutionSchedule() throws Exception
{
   MockHttpServletRequest request = new MockHttpServletRequest();
   request.addParameter("parameterName", "someValue");
   assertTrue("Batch is Completed :", returnPointsRatingDisputeFrom.checkBatchExecutionSchedule(request));
}