.../EntityResource/EntityResourceTestBase.php          | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
index edd5a0f..c72f065 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
@@ -147,6 +147,15 @@ protected function provisionEntityResource() {
   }
 
   /**
+   * Deprovisions the tested entity resource.
+   */
+  protected function deprovisionEntityResource() {
+    $this->resourceConfigStorage->load('entity.' . static::$entityTypeId)
+      ->delete();
+    $this->refreshTestStateAfterRestConfigChange();
+  }
+
+  /**
    * {@inheritdoc}
    */
   public function setUp() {
@@ -410,6 +419,15 @@ public function testGet() {
     $this->assertResourceResponse(200, FALSE, $response);
 
 
+    $this->deprovisionEntityResource();
+
+
+    // DX: upon deprovisioning, immediate 404, or 403 if canonical route.
+    $response = $this->request('GET', $url, $request_options);
+    $this->assertSame($has_canonical_url ? 403 : 404, $response->getStatusCode());
+
+
+    $this->provisionEntityResource();
     $url->setOption('query', ['_format' => 'non_existing_format']);