.../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 0eab9d7..1c1c83c 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php
@@ -440,14 +440,20 @@ 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) {
+            $found_cached_200_response = TRUE;
+          }
+          else if (!$cached_response->isClientError()) {
+            $other_cached_responses_are_4xx = FALSE;
+          }
           $this->assertNotInstanceOf(ResourceResponseInterface::class, $cached_response);
           $this->assertInstanceOf(CacheableResponseInterface::class, $cached_response);
         }
@@ -456,7 +462,8 @@ 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 {
       $this->assertResourceResponse(200, FALSE, $response, $this->getExpectedCacheTags(), $this->getExpectedCacheContexts(), static::$auth ? FALSE : 'HIT', FALSE);