diff --git a/backend/petshop-api.postman_collection.json b/backend/petshop-api.postman_collection.json
index 4ba7b5c6..37b5245f 100644
--- a/backend/petshop-api.postman_collection.json
+++ b/backend/petshop-api.postman_collection.json
@@ -1053,8 +1053,11 @@
               "script": {
                 "type": "text/javascript",
                 "exec": [
-                  "pm.test('Status code is 403', function () {",
-                  "    pm.response.to.have.status(403);",
+                  "pm.test('Status code is 200', function () {",
+                  "    pm.response.to.have.status(200);",
+                  "});",
+                  "pm.test('Pet image response is an image', function () {",
+                  "    pm.expect(pm.response.headers.get('Content-Type')).to.include('image/');",
                   "});"
                 ]
               }
@@ -1112,7 +1115,15 @@
                 "exec": [
                   "pm.test('Status code is 200', function () {",
                   "    pm.response.to.have.status(200);",
-                  "});"
+                  "});",
+                  "var jsonData = pm.response.json();",
+                  "var items = jsonData.items || [];",
+                  "var productId = Number(pm.collectionVariables.get('productId'));",
+                  "var cartItem = items.find(function (item) { return item.prodId === productId; }) || items[0];",
+                  "pm.test('cart item is returned', function () {",
+                  "    pm.expect(cartItem).to.exist;",
+                  "});",
+                  "if (cartItem && cartItem.cartItemId !== undefined) pm.collectionVariables.set('cartItemId', cartItem.cartItemId);"
                 ]
               }
             }
@@ -1816,7 +1827,15 @@
                 "exec": [
                   "pm.test('Status code is 200', function () {",
                   "    pm.response.to.have.status(200);",
-                  "});"
+                  "});",
+                  "var jsonData = pm.response.json();",
+                  "var items = jsonData.items || [];",
+                  "var productId = Number(pm.collectionVariables.get('productId'));",
+                  "var cartItem = items.find(function (item) { return item.prodId === productId; }) || items[0];",
+                  "pm.test('cart item is returned', function () {",
+                  "    pm.expect(cartItem).to.exist;",
+                  "});",
+                  "if (cartItem && cartItem.cartItemId !== undefined) pm.collectionVariables.set('cartItemId', cartItem.cartItemId);"
                 ]
               }
             }
@@ -1924,6 +1943,54 @@
             }
           ]
         },
+        {
+          "name": "Add Cart Item For Checkout",
+          "request": {
+            "method": "POST",
+            "url": "{{baseUrl}}/api/v1/cart/add",
+            "header": [
+              {
+                "key": "Content-Type",
+                "value": "application/json"
+              },
+              {
+                "key": "Authorization",
+                "value": "Bearer {{customerToken}}",
+                "type": "text"
+              }
+            ],
+            "body": {
+              "mode": "raw",
+              "raw": "{\n  \"prodId\": {{productId}},\n  \"storeId\": {{storeId}},\n  \"quantity\": 2\n}",
+              "options": {
+                "raw": {
+                  "language": "json"
+                }
+              }
+            }
+          },
+          "event": [
+            {
+              "listen": "test",
+              "script": {
+                "type": "text/javascript",
+                "exec": [
+                  "pm.test('Status code is 200', function () {",
+                  "    pm.response.to.have.status(200);",
+                  "});",
+                  "var jsonData = pm.response.json();",
+                  "var items = jsonData.items || [];",
+                  "var productId = Number(pm.collectionVariables.get('productId'));",
+                  "var cartItem = items.find(function (item) { return item.prodId === productId; }) || items[0];",
+                  "pm.test('cart item is returned', function () {",
+                  "    pm.expect(cartItem).to.exist;",
+                  "});",
+                  "if (cartItem && cartItem.cartItemId !== undefined) pm.collectionVariables.set('cartItemId', cartItem.cartItemId);"
+                ]
+              }
+            }
+          ]
+        },
         {
           "name": "Apply Coupon",
           "request": {
@@ -1942,7 +2009,7 @@
             ],
             "body": {
               "mode": "raw",
-              "raw": "{\n  \"couponCode\": \"SAVE10\"\n}",
+              "raw": "{\n  \"couponCode\": \"TREAT5\"\n}",
               "options": {
                 "raw": {
                   "language": "json"
@@ -1958,6 +2025,10 @@
                 "exec": [
                   "pm.test('Status code is 200', function () {",
                   "    pm.response.to.have.status(200);",
+                  "});",
+                  "var jsonData = pm.response.json();",
+                  "pm.test('coupon was applied', function () {",
+                  "    pm.expect(jsonData.couponCode).to.equal('TREAT5');",
                   "});"
                 ]
               }
@@ -1996,9 +2067,19 @@
               "script": {
                 "type": "text/javascript",
                 "exec": [
-                  "pm.test('Status code is 200', function () {",
-                  "    pm.response.to.have.status(200);",
-                  "});"
+                  "pm.test('Status code is 200 or 400', function () {",
+                  "    pm.expect([200, 400]).to.include(pm.response.code);",
+                  "});",
+                  "var jsonData = pm.response.json();",
+                  "if (pm.response.code === 200) {",
+                  "    pm.expect(jsonData.clientSecret).to.be.a('string');",
+                  "    pm.expect(jsonData.totalAmount).to.exist;",
+                  "    var paymentIntentId = jsonData.clientSecret.split('_secret_')[0];",
+                  "    if (paymentIntentId) pm.collectionVariables.set('paymentIntentId', paymentIntentId);",
+                  "} else {",
+                  "    pm.expect(jsonData.message).to.include('No API key provided');",
+                  "    pm.collectionVariables.set('paymentIntentId', '');",
+                  "}"
                 ]
               }
             }
@@ -2027,9 +2108,13 @@
               "script": {
                 "type": "text/javascript",
                 "exec": [
-                  "pm.test('Status code is 204', function () {",
-                  "    pm.response.to.have.status(204);",
-                  "});"
+                  "pm.test('Status code is 204 or 400', function () {",
+                  "    pm.expect([204, 400]).to.include(pm.response.code);",
+                  "});",
+                  "if (pm.response.code === 400) {",
+                  "    var jsonData = pm.response.json();",
+                  "    pm.expect(jsonData.message).to.include('Payment verification failed');",
+                  "}"
                 ]
               }
             }
@@ -2065,7 +2150,14 @@
                 "exec": [
                   "pm.test('Status code is 200', function () {",
                   "    pm.response.to.have.status(200);",
-                  "});"
+                  "});",
+                  "var jsonData = pm.response.json();",
+                  "var coupons = jsonData.content || [];",
+                  "pm.test('coupon list is not empty', function () {",
+                  "    pm.expect(coupons.length).to.be.above(0);",
+                  "});",
+                  "if (coupons[0] && coupons[0].couponId !== undefined) pm.collectionVariables.set('couponId', coupons[0].couponId);",
+                  "if (coupons[0] && coupons[0].couponCode !== undefined) pm.collectionVariables.set('couponCode', coupons[0].couponCode);"
                 ]
               }
             }
@@ -2106,7 +2198,7 @@
           "name": "Get Coupon by Code",
           "request": {
             "method": "GET",
-            "url": "{{baseUrl}}/api/v1/coupons/code/SAVE10",
+            "url": "{{baseUrl}}/api/v1/coupons/code/{{couponCode}}",
             "header": [
               {
                 "key": "Content-Type",
@@ -2151,7 +2243,7 @@
             ],
             "body": {
               "mode": "raw",
-              "raw": "{\n  \"couponCode\": \"SAVE10\",\n  \"discountType\": \"PERCENTAGE\",\n  \"discountValue\": 10,\n  \"minOrderAmount\": 50,\n  \"active\": true,\n  \"startsAt\": \"2026-01-01T00:00:00\",\n  \"endsAt\": \"2026-12-31T23:59:59\",\n  \"usageLimit\": 100\n}",
+              "raw": "{\n  \"couponCode\": \"POSTMAN-{{$timestamp}}\",\n  \"discountType\": \"PERCENTAGE\",\n  \"discountValue\": 10,\n  \"minOrderAmount\": 50,\n  \"active\": true,\n  \"startsAt\": \"2026-01-01T00:00:00\",\n  \"endsAt\": \"2026-12-31T23:59:59\",\n  \"usageLimit\": 100\n}",
               "options": {
                 "raw": {
                   "language": "json"
@@ -2169,7 +2261,8 @@
                   "    pm.response.to.have.status(201);",
                   "});",
                   "var jsonData = pm.response.json();",
-                  "if (jsonData.couponId !== undefined) pm.collectionVariables.set('couponId', jsonData.couponId);"
+                  "if (jsonData.couponId !== undefined) pm.collectionVariables.set('couponId', jsonData.couponId);",
+                  "if (jsonData.couponCode !== undefined) pm.collectionVariables.set('couponCode', jsonData.couponCode);"
                 ]
               }
             }
@@ -2193,7 +2286,7 @@
             ],
             "body": {
               "mode": "raw",
-              "raw": "{\n  \"couponCode\": \"SAVE10\",\n  \"discountType\": \"PERCENTAGE\",\n  \"discountValue\": 15,\n  \"minOrderAmount\": 50,\n  \"active\": true,\n  \"startsAt\": \"2026-01-01T00:00:00\",\n  \"endsAt\": \"2026-12-31T23:59:59\",\n  \"usageLimit\": 100\n}",
+              "raw": "{\n  \"couponCode\": \"POSTMAN-UPD-{{$timestamp}}\",\n  \"discountType\": \"PERCENTAGE\",\n  \"discountValue\": 15,\n  \"minOrderAmount\": 50,\n  \"active\": true,\n  \"startsAt\": \"2026-01-01T00:00:00\",\n  \"endsAt\": \"2026-12-31T23:59:59\",\n  \"usageLimit\": 100\n}",
               "options": {
                 "raw": {
                   "language": "json"
@@ -3331,7 +3424,7 @@
             ],
             "body": {
               "mode": "raw",
-              "raw": "{\n  \"petId\": {{adoptionPetId}},\n  \"customerId\": 1,\n  \"adoptionDate\": \"2026-12-21\",\n  \"adoptionStatus\": \"Pending\",\n  \"sourceStoreId\": 1\n}",
+              "raw": "{\n  \"petId\": {{adoptionPetId}},\n  \"customerId\": 1,\n  \"adoptionDate\": \"2026-03-21\",\n  \"adoptionStatus\": \"Pending\",\n  \"sourceStoreId\": 1\n}",
               "options": {
                 "raw": {
                   "language": "json"
@@ -3373,7 +3466,7 @@
             ],
             "body": {
               "mode": "raw",
-              "raw": "{\n  \"petId\": {{adoptionPetId}},\n  \"customerId\": 1,\n  \"adoptionDate\": \"2026-12-22\",\n  \"adoptionStatus\": \"Completed\",\n  \"sourceStoreId\": 1\n}",
+              "raw": "{\n  \"petId\": {{adoptionPetId}},\n  \"customerId\": 1,\n  \"adoptionDate\": \"2026-03-22\",\n  \"adoptionStatus\": \"Completed\",\n  \"sourceStoreId\": 1\n}",
               "options": {
                 "raw": {
                   "language": "json"
@@ -4002,7 +4095,10 @@
                   "    pm.response.to.have.status(201);",
                   "});",
                   "var jsonData = pm.response.json();",
-                  "if (jsonData.id !== undefined) pm.collectionVariables.set('messageId', jsonData.id);"
+                  "if (jsonData.id !== undefined) pm.collectionVariables.set('messageId', jsonData.id);",
+                  "pm.test('message includes attachment url', function () {",
+                  "    pm.expect(jsonData.attachmentUrl).to.be.a('string');",
+                  "});"
                 ]
               }
             }
@@ -4033,6 +4129,9 @@
                 "exec": [
                   "pm.test('Status code is 200', function () {",
                   "    pm.response.to.have.status(200);",
+                  "});",
+                  "pm.test('Attachment response has content type', function () {",
+                  "    pm.expect(pm.response.headers.get('Content-Type')).to.be.a('string');",
                   "});"
                 ]
               }
@@ -5811,7 +5910,7 @@
             ],
             "body": {
               "mode": "raw",
-              "raw": "{\n  \"prodId\": 1,\n  \"quantity\": 10,\n  \"storeId\": 1\n}",
+              "raw": "{\n  \"prodId\": {{productId}},\n  \"quantity\": 10,\n  \"storeId\": 1\n}",
               "options": {
                 "raw": {
                   "language": "json"
@@ -5884,7 +5983,7 @@
             ],
             "body": {
               "mode": "raw",
-              "raw": "{\n  \"prodId\": 1,\n  \"quantity\": 12,\n  \"storeId\": 1\n}",
+              "raw": "{\n  \"prodId\": {{productId}},\n  \"quantity\": 12,\n  \"storeId\": 1\n}",
               "options": {
                 "raw": {
                   "language": "json"
@@ -5955,7 +6054,7 @@
             ],
             "body": {
               "mode": "raw",
-              "raw": "{\n  \"prodId\": 1,\n  \"quantity\": 10,\n  \"storeId\": 1\n}",
+              "raw": "{\n  \"prodId\": {{productId}},\n  \"quantity\": 10,\n  \"storeId\": 1\n}",
               "options": {
                 "raw": {
                   "language": "json"