diff --git a/back/src/Model/Group.ts b/back/src/Model/Group.ts
index caf9b926..eacd2d03 100644
--- a/back/src/Model/Group.ts
+++ b/back/src/Model/Group.ts
@@ -1,4 +1,4 @@
-import { World } from "./World";
+import { World, ConnectCallback, DisconnectCallback } from "./World";
 import { UserInterface } from "./UserInterface";
 import {PositionInterface} from "_Model/PositionInterface";
 
@@ -6,11 +6,11 @@ export class Group {
     static readonly MAX_PER_GROUP = 4;
 
     private users: UserInterface[];
-    private connectCallback: (user1: string, user2: string) => void;
-    private disconnectCallback: (user1: string, user2: string) => void;
+    private connectCallback: ConnectCallback;
+    private disconnectCallback: DisconnectCallback;
 
 
-    constructor(users: UserInterface[], connectCallback: (user1: string, user2: string) => void, disconnectCallback: (user1: string, user2: string) => void) {
+    constructor(users: UserInterface[], connectCallback: ConnectCallback, disconnectCallback: DisconnectCallback) {
         this.users = [];
         this.connectCallback = connectCallback;
         this.disconnectCallback = disconnectCallback;
@@ -54,9 +54,7 @@ export class Group {
     join(user: UserInterface): void
     {
         // Broadcast on the right event
-        this.users.forEach((groupUser: UserInterface) => {
-            this.connectCallback(user.id, groupUser.id);
-        });
+        this.connectCallback(user.id, this);
         this.users.push(user);
         user.group = this;
     }
@@ -105,9 +103,7 @@ export class Group {
         user.group = undefined;
 
         // Broadcast on the right event
-        this.users.forEach((groupUser: UserInterface) => {
-            this.disconnectCallback(user.id, groupUser.id);
-        });
+        this.disconnectCallback(user.id, this);
     }
 
     /**
diff --git a/back/src/Model/World.ts b/back/src/Model/World.ts
index 795cc8be..b04b34ee 100644
--- a/back/src/Model/World.ts
+++ b/back/src/Model/World.ts
@@ -6,6 +6,9 @@ import {UserInterface} from "./UserInterface";
 import {ExSocketInterface} from "_Model/Websocket/ExSocketInterface";
 import {PositionInterface} from "_Model/PositionInterface";
 
+export type ConnectCallback = (user: string, group: Group) => void;
+export type DisconnectCallback = (user: string, group: Group) => void;
+
 export class World {
     static readonly MIN_DISTANCE = 160;
 
@@ -13,10 +16,10 @@ export class World {
     private users: Map<string, UserInterface>;
     private groups: Group[];
 
-    private connectCallback: (user1: string, user2: string) => void;
-    private disconnectCallback: (user1: string, user2: string) => void;
+    private connectCallback: ConnectCallback;
+    private disconnectCallback: DisconnectCallback;
 
-    constructor(connectCallback: (user1: string, user2: string) => void, disconnectCallback: (user1: string, user2: string) => void)
+    constructor(connectCallback: ConnectCallback, disconnectCallback: DisconnectCallback)
     {
         this.users = new Map<string, UserInterface>();
         this.groups = [];
diff --git a/back/tests/WorldTest.ts b/back/tests/WorldTest.ts
index 1d499727..7fbd88de 100644
--- a/back/tests/WorldTest.ts
+++ b/back/tests/WorldTest.ts
@@ -1,6 +1,6 @@
 import "jasmine";
 import {Message} from "../src/Model/Websocket/Message";
-import {World} from "../src/Model/World";
+import {World, ConnectCallback, DisconnectCallback } from "../src/Model/World";
 import {MessageUserPosition, Point} from "../src/Model/Websocket/MessageUserPosition";
 import { Group } from "../src/Model/Group";
 import {Distance} from "../src/Model//Distance";
@@ -8,10 +8,10 @@ import {Distance} from "../src/Model//Distance";
 describe("World", () => {
     it("should connect user1 and user2", () => {
         let connectCalled: boolean = false;
-        let connect = (user1: string, user2: string): void => {
+        let connect = (user: string, group: Group): void => {
             connectCalled = true;
         }
-        let disconnect = (user1: string, user2: string): void => {
+        let disconnect = (user: string, group: Group): void => {
 
         }
 
@@ -56,10 +56,10 @@ describe("World", () => {
 
     it("should connect 3 users", () => {
         let connectCalled: boolean = false;
-        let connect = (user1: string, user2: string): void => {
+        let connect = (user: string, group: Group): void => {
             connectCalled = true;
         }
-        let disconnect = (user1: string, user2: string): void => {
+        let disconnect = (user: string, group: Group): void => {
 
         }
 
@@ -101,10 +101,10 @@ describe("World", () => {
     it("should disconnect user1 and user2", () => {
         let connectCalled: boolean = false;
         let disconnectCalled: boolean = false;
-        let connect = (user1: string, user2: string): void => {
+        let connect = (user: string, group: Group): void => {
             connectCalled = true;
         }
-        let disconnect = (user1: string, user2: string): void => {
+        let disconnect = (user: string, group: Group): void => {
             disconnectCalled = true;
         }
 
@@ -142,51 +142,4 @@ describe("World", () => {
         expect(disconnectCalled).toBe(false);
     });
 
-    /**
-    it('Should return the distances between all users', () => {
-        let connectCalled: boolean = false;
-        let connect = (user1: string, user2: string): void => {
-            connectCalled = true;
-        }
-        let disconnect = (user1: string, user2: string): void => {
-
-        }
-
-        let world = new World(connect, disconnect);
-        let user1 = new MessageUserPosition({
-            userId: "foo",
-            roomId: 1,
-            position: new Point(100, 100)
-        });
-
-        world.join(user1);
-
-        let user2 = new MessageUserPosition({
-            userId: "bar",
-            roomId: 1,
-            position: new Point(500, 100)
-        });
-        world.join(user2);
-
-        let user3 = new MessageUserPosition({
-            userId: "baz",
-            roomId: 1,
-            position: new Point(101, 100)
-        });
-
-        let user4 = new MessageUserPosition({
-            userId: "buz",
-            roomId: 1,
-            position: new Point(105, 100)
-        })
-
-        let group = new Group([user1, user2, user3, user4]);
-
-        let distances = world.getDistancesBetweenGroupUsers(group)
-
-        console.log(distances);
-
-        //expect(distances).toBe([]);
-    })
-    **/
 })