diff --git a/core/tests/Drupal/Tests/Component/Cache/FileCacheTest.php b/core/tests/Drupal/Tests/Component/Cache/FileCacheTest.php
index f2db88e..0c9ee22 100644
--- a/core/tests/Drupal/Tests/Component/Cache/FileCacheTest.php
+++ b/core/tests/Drupal/Tests/Component/Cache/FileCacheTest.php
@@ -145,7 +145,7 @@ public function testDelete() {
     $result = $this->staticFileCache->fetch([$cid]);
     $this->assertEquals([], $result);
 
-    $result = $this->fileCache->get($cid);
+    $result = $this->fileCache->get($filename);
     $this->assertNull($result);
   }
 
diff --git a/core/tests/Drupal/Tests/Core/Cache/Fixtures/42.php b/core/tests/Drupal/Tests/Core/Cache/Fixtures/42.php
deleted file mode 100644
index 8c7eb97..0000000
--- a/core/tests/Drupal/Tests/Core/Cache/Fixtures/42.php
+++ /dev/null
@@ -1 +0,0 @@
-<?php return unserialize('i:42;');
diff --git a/core/tests/Drupal/Tests/Core/Cache/Fixtures/42.php.txt b/core/tests/Drupal/Tests/Core/Cache/Fixtures/42.php.txt
new file mode 100644
index 0000000..8c7eb97
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Cache/Fixtures/42.php.txt
@@ -0,0 +1 @@
+<?php return unserialize('i:42;');
diff --git a/core/tests/Drupal/Tests/Core/Cache/PhpStorageFileCacheBackendTest.php b/core/tests/Drupal/Tests/Core/Cache/PhpStorageFileCacheBackendTest.php
index af41ce8..77d4b5e 100644
--- a/core/tests/Drupal/Tests/Core/Cache/PhpStorageFileCacheBackendTest.php
+++ b/core/tests/Drupal/Tests/Core/Cache/PhpStorageFileCacheBackendTest.php
@@ -63,7 +63,7 @@ public function testFetch() {
     $this->storageMock->expects($this->once())
       ->method('getFullPath')
       ->with($this->equalTo($cid_hash))
-      ->willReturn(__DIR__ . '/Fixtures/42.php');
+      ->willReturn(__DIR__ . '/Fixtures/42.php.txt');
 
     $result = $this->cache->fetch([$cid]);
     $this->assertEquals([$cid => 42], $result);