.../Functional/EntityResource/EntityResourceTestBase.php  | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
index 41d9eec..ca7424d 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
@@ -430,14 +430,20 @@ public function testGet() {
             ':pattern' => '%[route]=rest.%',
           ])
           ->fetchAllAssoc('cid');
-        $this->assertCount(2, $cache_items);
+        $this->assertTrue(count($cache_items) >= 2);
         $found_cache_redirect = FALSE;
-        $found_cached_response = FALSE;
+        $found_cached_200_response = FALSE;
+        $other_cached_responses_are_4xx = TRUE;
         foreach ($cache_items as $cid => $cache_item) {
           $cached_data = unserialize($cache_item->data);
           if (!isset($cached_data['#cache_redirect'])) {
-            $found_cached_response = TRUE;
             $cached_response = $cached_data['#response'];
+            if ($cached_response->getStatusCode() === 200) {
+              $found_cached_200_response = TRUE;
+            }
+            elseif (!$cached_response->isClientError()) {
+              $other_cached_responses_are_4xx = FALSE;
+            }
             $this->assertNotInstanceOf(ResourceResponseInterface::class, $cached_response);
             $this->assertInstanceOf(CacheableResponseInterface::class, $cached_response);
           }
@@ -446,7 +452,8 @@ public function testGet() {
           }
         }
         $this->assertTrue($found_cache_redirect);
-        $this->assertTrue($found_cached_response);
+        $this->assertTrue($found_cached_200_response);
+        $this->assertTrue($other_cached_responses_are_4xx);
       }
     }
     else {