diff --git a/api/src/controllers/group.ts b/api/src/controllers/group.ts
index 3a6ff66..9a3bc40 100644
--- a/api/src/controllers/group.ts
+++ b/api/src/controllers/group.ts
@@ -20,7 +20,7 @@ export interface GroupResponse {
   description: string
 }
 
-interface GroupDetailsResponse {
+export interface GroupDetailsResponse {
   groupId: number
   name: string
   description: string
@@ -249,9 +249,10 @@ const updateUsersListInGroup = async (
       message: 'User not found.'
     }
 
-  const updatedGroup = (action === 'addUser'
-    ? await group.addUser(user._id)
-    : await group.removeUser(user._id)) as unknown as GroupDetailsResponse
+  const updatedGroup =
+    action === 'addUser'
+      ? await group.addUser(user)
+      : await group.removeUser(user)
 
   if (!updatedGroup)
     throw {
@@ -260,9 +261,6 @@ const updateUsersListInGroup = async (
       message: 'Unable to update group.'
     }
 
-  if (action === 'addUser') user.addGroup(group._id)
-  else user.removeGroup(group._id)
-
   return {
     groupId: updatedGroup.groupId,
     name: updatedGroup.name,
diff --git a/api/src/model/Group.ts b/api/src/model/Group.ts
index 36b7842..6341825 100644
--- a/api/src/model/Group.ts
+++ b/api/src/model/Group.ts
@@ -1,5 +1,6 @@
 import mongoose, { Schema, model, Document, Model } from 'mongoose'
-import User from './User'
+import { GroupDetailsResponse } from '../controllers'
+import User, { IUser } from './User'
 const AutoIncrement = require('mongoose-sequence')(mongoose)
 
 export interface GroupPayload {
@@ -27,8 +28,9 @@ interface IGroupDocument extends GroupPayload, Document {
 }
 
 interface IGroup extends IGroupDocument {
-  addUser(userObjectId: Schema.Types.ObjectId): Promise<IGroup>
-  removeUser(userObjectId: Schema.Types.ObjectId): Promise<IGroup>
+  addUser(user: IUser): Promise<GroupDetailsResponse>
+  removeUser(user: IUser): Promise<GroupDetailsResponse>
+  hasUser(user: IUser): boolean
 }
 interface IGroupModel extends Model<IGroup> {}
 
@@ -70,28 +72,31 @@ groupSchema.pre('remove', async function () {
 })
 
 // Instance Methods
-groupSchema.method(
-  'addUser',
-  async function (userObjectId: Schema.Types.ObjectId) {
-    const userIdIndex = this.users.indexOf(userObjectId)
-    if (userIdIndex === -1) {
-      this.users.push(userObjectId)
-    }
-    this.markModified('users')
-    return this.save()
+groupSchema.method('addUser', async function (user: IUser) {
+  const userObjectId = user._id
+  const userIdIndex = this.users.indexOf(userObjectId)
+  if (userIdIndex === -1) {
+    this.users.push(userObjectId)
+    user.addGroup(this._id)
   }
-)
-groupSchema.method(
-  'removeUser',
-  async function (userObjectId: Schema.Types.ObjectId) {
-    const userIdIndex = this.users.indexOf(userObjectId)
-    if (userIdIndex > -1) {
-      this.users.splice(userIdIndex, 1)
-    }
-    this.markModified('users')
-    return this.save()
+  this.markModified('users')
+  return this.save()
+})
+groupSchema.method('removeUser', async function (user: IUser) {
+  const userObjectId = user._id
+  const userIdIndex = this.users.indexOf(userObjectId)
+  if (userIdIndex > -1) {
+    this.users.splice(userIdIndex, 1)
+    user.removeGroup(this._id)
   }
-)
+  this.markModified('users')
+  return this.save()
+})
+groupSchema.method('hasUser', function (user: IUser) {
+  const userObjectId = user._id
+  const userIdIndex = this.users.indexOf(userObjectId)
+  return userIdIndex > -1
+})
 
 export const Group: IGroupModel = model<IGroup, IGroupModel>(
   'Group',
diff --git a/api/src/model/User.ts b/api/src/model/User.ts
index b70807d..dd0123b 100644
--- a/api/src/model/User.ts
+++ b/api/src/model/User.ts
@@ -35,6 +35,7 @@ export interface UserPayload {
 }
 
 interface IUserDocument extends UserPayload, Document {
+  _id: Schema.Types.ObjectId
   id: number
   isAdmin: boolean
   isActive: boolean
@@ -43,7 +44,7 @@ interface IUserDocument extends UserPayload, Document {
   tokens: [{ [key: string]: string }]
 }
 
-interface IUser extends IUserDocument {
+export interface IUser extends IUserDocument {
   comparePassword(password: string): boolean
   addGroup(groupObjectId: Schema.Types.ObjectId): Promise<IUser>
   removeGroup(groupObjectId: Schema.Types.ObjectId): Promise<IUser>