package impl;

 import api.BetterInstanceProvider;

 import api.InstanceProvider;

 import org.junit.After;

 import org.junit.AfterClass;

 import org.junit.Before;

 import org.junit.BeforeClass;

 import org.junit.Test;

 import static org.junit.Assert.*;

 public class InstanceProviderTest {

     public InstanceProviderTest() {

     }

     @BeforeClass

     public static void setUpClass() throws Exception {

     }

     @AfterClass

     public static void tearDownClass() throws Exception {

     }

     @Before

     public void setUp() {

     }

     @After

     public void tearDown() {

     }

     @Test

     public void verifyBehaviourOnOldInterface() {

         class IP implements InstanceProvider {

             int instanceClass;

             int instanceCreate;

             public Class<?> instanceClass() {

                 instanceClass++;

                 return String.class;

             }

             public Object instanceCreate() {

                 instanceCreate++;

                 return "API Design!";

             }

         }

         IP instance = new IP();

         boolean isString = checkIsString(instance);

         assertTrue("Provides string", isString);

         assertEquals("Class was tested", 1, instance.instanceClass);

         assertEquals("No instance created", 0, instance.instanceCreate);

     }

     @Test

     public void verifyBehaviourOnNewInterface() {

         class IP implements BetterInstanceProvider {

             int isInstanceOf;

             int instanceClass;

             int instanceCreate;

             public Class<?> instanceClass() {

                 instanceClass++;

                 return String.class;

             }

             public Object instanceCreate() {

                 instanceCreate++;

                 return "API Design!";

             }

             public boolean isInstanceOf(Class<?> c) {

                 isInstanceOf++;

                 return c.isAssignableFrom(String.class);

             }

         }

         IP instance = new IP();

         boolean isString = checkIsString(instance);

         assertTrue("Provides string", isString);

         assertEquals("Class was not tested", 0, instance.instanceClass);

         assertEquals("No instance created", 0, instance.instanceCreate);

         assertEquals("isInstanceOf called", 1, instance.isInstanceOf);

     }

     private static boolean checkIsString(InstanceProvider instance) {

         // BEGIN: instanceof.Use

         if (instance instanceof BetterInstanceProvider) {

             BetterInstanceProvider bip = (BetterInstanceProvider)instance;

             return bip.isInstanceOf(String.class);

         } else {

             return String.class.isAssignableFrom(instance.instanceClass());

         }

         // END: instanceof.Use

     }

 }