diff --git a/apps/wallet/serializers.py b/apps/wallet/serializers.py
index ecdff32..b019269 100755
--- a/apps/wallet/serializers.py
+++ b/apps/wallet/serializers.py
@@ -1,4 +1,5 @@
 from django.db import IntegrityError
+from django.core.validators import MinValueValidator
 from django.db.transaction import atomic
 from rest_framework import serializers
 from rest_framework.exceptions import APIException
@@ -175,7 +176,7 @@ class ApplicationTransactionSerializer(BaseTransactionSerializer):
 class ApplicationDepositSerializer(serializers.ModelSerializer):
     payee_id = serializers.UUIDField(required=True)
     payee_type = serializers.IntegerField(required=True)
-    amount = serializers.IntegerField(required=True)
+    amount = serializers.IntegerField(required=True, validators=[MinValueValidator(1)])
     # TODO: details as fields
 
     class Meta:
@@ -200,7 +201,7 @@ class ApplicationDepositSerializer(serializers.ModelSerializer):
 class ApplicationWithdrawSerializer(serializers.ModelSerializer):
     payer_id = serializers.UUIDField(required=True)
     payer_type = serializers.IntegerField(required=True)
-    amount = serializers.IntegerField(required=True)
+    amount = serializers.IntegerField(required=True, validators=[MinValueValidator(1)])
 
     class Meta:
         model = Transaction
diff --git a/apps/wallet/tests/application.py b/apps/wallet/tests/application.py
index f0c5edc..7b8b425 100755
--- a/apps/wallet/tests/application.py
+++ b/apps/wallet/tests/application.py
@@ -22,6 +22,18 @@ class ApplicationApiFlowsTests(APITestCase):
     application_uuid = uuid.UUID('b14e8b86-8f4a-44d9-b29d-badceb470053')
     client_id = '4INGOCMoulE0fNY1SQlTbPtsWqqxGj2DdqjADq6u'
 
+    scopes = [
+        'wallet.application.deposit:verify',
+        'wallet.application:get_balance',
+        'wallet.application.deposit:submit',
+        'wallet.deposit:submit',
+        'wallet.wallet:get_balance',
+        'wallet.application:get_user_balance',
+
+        'wallet.application.withdraw:submit',
+        'wallet.application.withdraw:verify',
+    ]
+
     def setUp(self):
         self.application_user, _ = User.objects.get_or_create(pk=self.application_uuid)
         self.payer_user, _ = User.objects.get_or_create(pk=self.payer_uuid)
@@ -31,18 +43,6 @@ class ApplicationApiFlowsTests(APITestCase):
         expire_datetime = timezone.now() + timedelta(seconds=3600)
         expire_datetime.isoformat()
 
-        scopes = [
-            'wallet.application.deposit:verify',
-            'wallet.application:get_balance',
-            'wallet.application.deposit:submit',
-            'wallet.deposit:submit',
-            'wallet.wallet:get_balance',
-            'wallet.application:get_user_balance',
-
-            'wallet.application.withdraw:submit',
-            'wallet.application.withdraw:verify',
-        ]
-
         self.application_access_token, _created = AccessToken.objects.update_or_create(
             token=self.application_access_token,
             defaults={
@@ -50,7 +50,7 @@ class ApplicationApiFlowsTests(APITestCase):
                 "client_id": self.client_id,
                 # "client_owner": owner,
                 "application_id": self.application_uuid,
-                "scope": ' '.join(scopes),
+                "scope": ' '.join(self.scopes),
                 "expires": expire_datetime.isoformat(),
             },
         )
@@ -62,7 +62,7 @@ class ApplicationApiFlowsTests(APITestCase):
                 "client_id": self.client_id,
                 # "client_owner": owner,
                 "application_id": self.application_uuid,
-                "scope": ' '.join(scopes),
+                "scope": ' '.join(self.scopes),
                 "expires": expire_datetime.isoformat(),
             },
         )
@@ -83,6 +83,24 @@ class ApplicationApiFlowsTests(APITestCase):
         response = self.client.get(reverse('wallet:user_wallet_balance_api'), HTTP_AUTHORIZATION=auth)
         self.assertContains(response, 'balance')
 
+
+    def test_authentication_expired_token(self):
+        access_token = 'u4naVsdKCbKNOhnElPyXcrwSnqqFbm23'
+        expired_access_token, _created = AccessToken.objects.update_or_create(
+            token=access_token,
+            defaults={
+                "user": self.application_user,
+                "client_id": self.client_id,
+                # "client_owner": owner,
+                "application_id": self.application_uuid,
+                "scope": ' '.join(self.scopes),
+                "expires": (timezone.now() - timedelta(seconds=3600)).isoformat(),
+            },
+        )
+        auth = self._create_authorization_header(expired_access_token.token)
+        response = self.client.get(reverse('wallet:user_wallet_balance_api'), HTTP_AUTHORIZATION=auth)
+        self.assertEqual(response.status_code, 401)
+
     # def test_authentication_disallow(self):
     #     auth = self._create_authorization_header('fake_token')
     #     response = self.client.get(reverse('wallet:user_wallet_balance_api'), HTTP_AUTHORIZATION=auth)
@@ -154,6 +172,30 @@ class ApplicationApiFlowsTests(APITestCase):
         response = self.client.post(reverse('wallet:application_deposit_submit_api'), data=data, HTTP_AUTHORIZATION=auth)
         self.assertEqual(response.status_code, 500)
 
+    def test_deposit_flow_zero_amount(self):
+        auth = self._create_authorization_header(self.application_access_token.token)
+
+        # Deposit process
+        data = {
+            'amount': 0,
+            'payee_id': self.payee_uuid,
+            'payee_type': TypeChoices.USER
+        }
+        response = self.client.post(reverse('wallet:application_deposit_submit_api'), data=data, HTTP_AUTHORIZATION=auth)
+        self.assertEqual(response.status_code, 400)
+
+    def test_deposit_flow_negative_amount(self):
+        auth = self._create_authorization_header(self.application_access_token.token)
+
+        # Deposit process
+        data = {
+            'amount': -100,
+            'payee_id': self.payee_uuid,
+            'payee_type': TypeChoices.USER
+        }
+        response = self.client.post(reverse('wallet:application_deposit_submit_api'), data=data, HTTP_AUTHORIZATION=auth)
+        self.assertEqual(response.status_code, 400)
+
     def test_deposit_flow_prevent_double_spending(self):
         auth = self._create_authorization_header(self.application_access_token.token)
 
@@ -246,6 +288,32 @@ class ApplicationApiFlowsTests(APITestCase):
         response = self.client.post(reverse('wallet:application_withdraw_submit_api'), data=data, HTTP_AUTHORIZATION=auth)
         self.assertEqual(response.status_code, 500)
 
+    def test_withdraw_flow_zero_amount(self):
+        auth = self._create_authorization_header(self.payer_access_token.token)
+
+        # Deposit process
+        data = {
+            'amount': 0,
+            'payer_id': self.payer_uuid,
+            'payer_type': TypeChoices.USER
+        }
+        response = self.client.post(reverse('wallet:application_withdraw_submit_api'), data=data,
+                                    HTTP_AUTHORIZATION=auth)
+        self.assertEqual(response.status_code, 400)
+
+    def test_withdraw_flow_negative_amount(self):
+        auth = self._create_authorization_header(self.payer_access_token.token)
+
+        # Deposit process
+        data = {
+            'amount': -500,
+            'payer_id': self.payer_uuid,
+            'payer_type': TypeChoices.USER
+        }
+        response = self.client.post(reverse('wallet:application_withdraw_submit_api'), data=data,
+                                    HTTP_AUTHORIZATION=auth)
+        self.assertEqual(response.status_code, 400)
+
     def test_withdraw_flow_prevent_double_spending(self):
         auth = self._create_authorization_header(self.payer_access_token.token)