MC-22963: Identify and refactor GET requests that modify data.

Refactor Tax rate delete class to use POST.
Add integration test.

Author: admanesachin

app/code/Magento/Tax/Block/Adminhtml/Rate/Toolbar/Save.php

@@ -133,7 +133,7 @@ protected function _prepareLayout()
                     ) . '\', \'' . $this->getUrl(
                         'tax/*/delete',
                         ['rate' => $rate]
-                    ) . '\')',
+                    ) . '\', {data: {}})',
                     'class' => 'delete'
                 ]
             );

app/code/Magento/Tax/Controller/Adminhtml/Rate/Delete.php

@@ -8,8 +8,9 @@
 
 use Magento\Framework\Exception\NoSuchEntityException;
 use Magento\Framework\Controller\ResultFactory;
+use Magento\Framework\App\Action\HttpPostActionInterface;
 
-class Delete extends \Magento\Tax\Controller\Adminhtml\Rate
+class Delete extends \Magento\Tax\Controller\Adminhtml\Rate implements HttpPostActionInterface
 {
     /**
      * Delete Rate and Data

dev/tests/integration/testsuite/Magento/Tax/Controller/Adminhtml/RateTest.php

@@ -6,6 +6,8 @@
 
 namespace Magento\Tax\Controller\Adminhtml;
 
+use Magento\Framework\App\Request\Http as HttpRequest;
+
 /**
  * @magentoAppArea adminhtml
  */
@@ -283,4 +285,34 @@ public function testAjaxNonLoadAction()
         $this->assertArrayHasKey('error_message', $result);
         $this->assertTrue(strlen($result['error_message'])>0);
     }
+
+    /** Test Delete Tax Rate
+     * @magentoAppIsolation enabled
+     * @magentoDbIsolation enabled
+     * @return void
+     */
+    public function testDeleteRate(): void
+    {
+        $rateId = 2;
+        $this->getRequest()->setMethod(HttpRequest::METHOD_POST);
+        $this->getRequest()->setPostValue(['rate' => $rateId]);
+        $this->dispatch('backend/tax/rate/delete');
+        $successMessage = (string)__('You deleted the tax rate.');
+        $this->assertSessionMessages($this->equalTo([$successMessage]));
+    }
+
+    /** Test Delete Incorrect Tax Rate
+     * @magentoAppIsolation enabled
+     * @magentoDbIsolation enabled
+     * @return void
+     */
+    public function testDeleteIncorrectRate(): void
+    {
+        $incorrectRateId = 20999;
+        $this->getRequest()->setMethod(HttpRequest::METHOD_POST);
+        $this->getRequest()->setPostValue(['rate' => $incorrectRateId]);
+        $this->dispatch('backend/tax/rate/delete');
+        $errorMessage = (string)_("We can't delete this rate because of an incorrect rate ID.");
+        $this->assertSessionMessages($this->equalTo([$errorMessage]));
+    }
 }