Covering the successfully adding a valid coupon to cart by an integra…

…tion test

dev/tests/integration/testsuite/Magento/Checkout/Controller/Cart/Index/CouponPostTest.php

@@ -36,4 +36,35 @@ public function testExecute()
             \Magento\Framework\Message\MessageInterface::TYPE_ERROR
         );
     }
+
+    /**
+     * Testing by adding a valid coupon to cart
+     *
+     * @magentoDataFixture Magento/Checkout/_files/quote_with_virtual_product_and_address.php
+     * @magentoDataFixture Magento/Usps/Fixtures/cart_rule_coupon_free_shipping.php
+     * @return void
+     */
+    public function testAddingValidCoupon(): void
+    {
+        /** @var $session \Magento\Checkout\Model\Session */
+        $session = $this->_objectManager->create(\Magento\Checkout\Model\Session::class);
+        $quote = $session->getQuote();
+        $quote->setData('trigger_recollect', 1)->setTotalsCollectedFlag(true);
+
+        $couponCode = 'IMPHBR852R61';
+        $inputData = [
+            'remove' => 0,
+            'coupon_code' => $couponCode
+        ];
+        $this->getRequest()->setMethod(HttpRequest::METHOD_POST);
+        $this->getRequest()->setPostValue($inputData);
+        $this->dispatch(
+            'checkout/cart/couponPost/'
+        );
+
+        $this->assertSessionMessages(
+            $this->equalTo(['You used coupon code "' . $couponCode . '".']),
+            \Magento\Framework\Message\MessageInterface::TYPE_SUCCESS
+        );
+    }
 }