src/main/java/com/zipcodewilmington/generic/group/Group.java

 import com.zipcodewilmington.generic.identifiables.IdentifiableInterface;
 
 import java.io.Serializable;
+import java.lang.reflect.Type;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.function.Predicate;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 /**
  * @author leon on 06/12/2018.
  */
-public class Group<ChangeThisTypeRespectively,ChangeThisOneToo> extends AbstractGroup{
+public class Group<TypeOfId extends Serializable,
+        TypeOfEntity extends IdentifiableInterface> extends AbstractGroup{
+
+    List<TypeOfEntity> list = new ArrayList<>();
+
     @Override
     public Integer count() {
-        return null;
+        return list.size();
     }
 
     @Override
     public void insert(IdentifiableInterface object) {
-
+        list.add((TypeOfEntity) object);
     }
 
     @Override
     public void delete(IdentifiableInterface object) {
-
+        list.remove(object);
     }
 
     @Override
     public void delete(Serializable serializable) {
-
+        for (int i = 0; i < list.size(); i++) {
+            if (list.get(i).getIdentity() == serializable) {
+                list.remove(list.get(i));
+            }
+        }
     }
 
     @Override
     public Boolean has(IdentifiableInterface object) {
-        return null;
+        return list.contains(object);
     }
 
     @Override
     public Boolean has(Serializable serializable) {
-        return null;
+        return list.contains(serializable);
     }
 
     @Override
-    public List filter(Predicate predicate) {
-        return null;
+    public List<TypeOfEntity> filter(Predicate predicate) {
+        return (List<TypeOfEntity>) list.stream().filter(predicate).collect(Collectors.toList());
     }
 
     @Override
     public Class getIdentityType() {
-        return null;
+        return list.get(0).getIdentity().getClass();
     }
 
     @Override
     public Class getIdentifiableType() {
-        return null;
+        return list.get(0).getClass();
     }
 
 }

src/main/java/com/zipcodewilmington/generic/identifiables/ActionFigure.java

  */
 public class ActionFigure implements IdentifiableInterface {
 
+    Long identity = 0L;
+
     @Override
     public Serializable getIdentity() {
-        return null;
+        return identity;
     }
 
     public Class getIdentityType() {
-        return null;
+        return identity.getClass();
     }
 }

src/main/java/com/zipcodewilmington/generic/identifiables/Person.java

  */
 public class Person implements IdentifiableInterface {
 
+    private String identity = "";
+
     @Override
     public Serializable getIdentity() {
-        return null;
+        return identity;
     }
 
     public Class getIdentityType() {
-        return null;
+        return identity.getClass();
     }
 }

src/test/java/com/zipcodewilmington/generic/group/CountTest.java

 
     @Test
     public void testRandom() {
-        test(Math.abs(new Random().nextInt()));
+        test(Math.abs(new Random().nextInt(100)));
     }
 
     private void test(Integer numberOfObjectsToAdd) {

src/test/java/com/zipcodewilmington/generic/group/DeleteByIdTest.java

 
     @Test
     public void testRandom() {
-        test(Math.abs(new Random().nextInt()));
+        test(Math.abs(new Random().nextInt(100)));
     }
 
     private void test(Integer numberOfObjectsToAdd) {

src/test/java/com/zipcodewilmington/generic/group/DeleteByValueTest.java

 
     @Test
     public void testRandom() {
-        test(Math.abs(new Random().nextInt()));
+        test(Math.abs(new Random().nextInt(100)));
     }
 
     private void test(Integer numberOfObjectsToAdd) {

src/test/java/com/zipcodewilmington/generic/group/FilterTest.java

 
     @Test
     public void testRandom() {
-        test(Math.abs(new Random().nextInt()));
+        test(Math.abs(new Random().nextInt(100)));
     }
 
 

src/test/java/com/zipcodewilmington/generic/group/GetIdentityTypeTest.java

 
     @Test
     public void testGetIdentityType() { // ༼∵༽ ༼⍨༽ ༼⍢༽ ༼⍤༽
+        personGroup.insert(new Person());
+        actionFigureGroup.insert(new ActionFigure());
         Assert.assertEquals(personGroup.getIdentityType(), String.class);
         Assert.assertEquals(actionFigureGroup.getIdentityType(), Long.class);
     }
 
     @Test
     public void testGetIdentifiableType() { // ヽ༼ ಠ益ಠ ༽ﾉ
+        personGroup.insert(new Person());
+        actionFigureGroup.insert(new ActionFigure());
         Assert.assertEquals(personGroup.getIdentifiableType(), Person.class);
         Assert.assertEquals(actionFigureGroup.getIdentifiableType(), ActionFigure.class);
     }

src/test/java/com/zipcodewilmington/generic/group/HasByIdTest.java

 
     @Test
     public void testRandom() {
-        test(Math.abs(new Random().nextInt()));
+        test(Math.abs(new Random().nextInt(100)));
     }
 
     private void test(Integer numberOfObjectsToAdd) {

src/test/java/com/zipcodewilmington/generic/group/InsertTest.java

 
     @Test
     public void testRandom() {
-        test(Math.abs(new Random().nextInt()));
+        test(Math.abs(new Random().nextInt(100)));
     }
 
     private void test(Integer numberOfObjectsToAdd) {
             group.insert(identifiable);
 
             // then
-            Assert.assertFalse(group.has(identifiable));
+            Assert.assertTrue(group.has(identifiable));
         }
     }
 }