Say I have the following code:

public class ClassToTest
{
    AnotherClass anotherClass;

    public void methodToTest( int x, int y )
    {
        int z = x + y
        anotherClass.receiveSomething( z );
    }
}

public class AnotherClass
{
    public void receiveSomething( int z ) {.. do something.. }  
}

I want to make assertion on the value of the variable z. How do I do this? Variables x, y, and z could be some other Java class types, and I just used "int" for simplicity.