diff -u b/core/lib/Drupal/Core/Cache/ArrayBackend.php b/core/lib/Drupal/Core/Cache/ArrayBackend.php
--- b/core/lib/Drupal/Core/Cache/ArrayBackend.php
+++ b/core/lib/Drupal/Core/Cache/ArrayBackend.php
@@ -99,9 +99,7 @@
     $this->cache[$cid] = (object) array(
       'cid' => $cid,
       'data' => $data,
-      // $expire is ignored because in the context of a static cache that
-      // persists for a single request it has no meaning.
-      'expire' => CACHE_PERMANENT,
+      'expire' => $expire,
       'tags' => $tags,
       'checksum' => $this->checksum($this->flattenTags($tags)),
     );
@@ -159,7 +157,8 @@
    * Implements Drupal\Core\Cache\CacheBackendInterface::expire().
    *
    * Cache expiration is not implemented for PHP ArrayBackend as this backend
-   * only persists during a single request.
+   * only persists during a single request and expiration are done using
+   * REQUEST_TIME.
    */
   public function expire() {
   }
diff -u b/core/modules/system/lib/Drupal/system/Tests/Cache/GenericBackendUnitTestBase.php b/core/modules/system/lib/Drupal/system/Tests/Cache/GenericBackendUnitTestBase.php
--- b/core/modules/system/lib/Drupal/system/Tests/Cache/GenericBackendUnitTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Cache/GenericBackendUnitTestBase.php
@@ -133,20 +133,18 @@
   public function testSetGet() {
     $backend = $this->getCacheBackend();
 
-    $cid = 'test1';
     $data = 7;
-    $this->assertIdentical(FALSE, $backend->get($cid), format_string("Backend does not contain data for cache id %cid.", array('%cid' => $cid)));
-    $backend->set($cid, $data);
-    $cached = $backend->get($cid);
-    $this->assert(is_object($cached), format_string("Backend returned an object for cache id %cid.", array('%cid' => $cid)));
+    $this->assertIdentical(FALSE, $backend->get('test1'), "Backend does not contain data for cache id test1.");
+    $backend->set('test1', $data);
+    $cached = $backend->get('test1');
+    $this->assert(is_object($cached), "Backend returned an object for cache id test1.");
     $this->assertIdentical($data, $cached->data);
 
-    $cid = 'test2';
     $data = array('value' => 3);
-    $this->assertIdentical(FALSE, $backend->get($cid), format_string("Backend does not contain data for cache id %cid.", array('%cid' => $cid)));
-    $backend->set($cid, $data);
-    $cached = $backend->get($cid);
-    $this->assert(is_object($cached), format_string("Backend returned an object for cache id %cid.", array('%cid' => $cid)));
+    $this->assertIdentical(FALSE, $backend->get('test2'), "Backend does not contain data for cache id test2.");
+    $backend->set('test2', $data);
+    $cached = $backend->get('test2');
+    $this->assert(is_object($cached), "Backend returned an object for cache id test2.");
     $this->assertIdentical($data, $cached->data);
   }
 
@@ -156,27 +154,22 @@
   public function testDelete() {
     $backend = $this->getCacheBackend();
 
-    $cid = 'test1';
-    $this->assertIdentical(FALSE, $backend->get($cid), format_string("Backend does not contain data for cache id %cid.", array('%cid' => $cid)));
-    $backend->set($cid, 7);
-    $this->assert(is_object($backend->get($cid)), format_string("Backend returned an object for cache id %cid.", array('%cid' => $cid)));
-
-    $cid = 'test2';
-    $this->assertIdentical(FALSE, $backend->get($cid), format_string("Backend does not contain data for cache id %cid.", array('%cid' => $cid)));
-    $backend->set($cid, 3);
-    $this->assert(is_object($backend->get($cid)), format_string("Backend returned an object for cache id %cid.", array('%cid' => $cid)));
-
-    $cid = 'test1';
-    $backend->delete($cid);
-    $this->assertIdentical(FALSE, $backend->get($cid), format_string("Backend does not contain data for cache id %cid after deletion.", array('%cid' => $cid)));
-
-    $cid = 'test2';
-    $cached = $backend->get($cid);
-    $this->assert(is_object($backend->get($cid)), format_string("Backend still has an object for cache id %cid.", array('%cid' => $cid)));
-
-    $cid = 'test2';
-    $backend->delete($cid);
-    $this->assertIdentical(FALSE, $backend->get($cid), format_string("Backend does not contain data for cache id %cid after deletion.", array('%cid' => $cid)));
+    $this->assertIdentical(FALSE, $backend->get('test1'), "Backend does not contain data for cache id test1.");
+    $backend->set('test1', 7);
+    $this->assert(is_object($backend->get('test1')), "Backend returned an object for cache id test1.");
+
+    $this->assertIdentical(FALSE, $backend->get('test2'), "Backend does not contain data for cache id test2.");
+    $backend->set('test2', 3);
+    $this->assert(is_object($backend->get('test2')), "Backend returned an object for cache id %cid.");
+
+    $backend->delete('test1');
+    $this->assertIdentical(FALSE, $backend->get('test1'), "Backend does not contain data for cache id test1 after deletion.");
+
+    $cached = $backend->get('test2');
+    $this->assert(is_object($backend->get('test2')), "Backend still has an object for cache id test2.");
+
+    $backend->delete('test2');
+    $this->assertIdentical(FALSE, $backend->get('test2'), "Backend does not contain data for cache id test2 after deletion.");
   }
 
   /**
@@ -263,10 +256,10 @@
     }
 
     // Test return array values.
-    $this->assertIdentical($ret['test2']->data, 3, "Existing key 2 has the correct value.");
-    $this->assertIdentical($ret['test3']->data, 5, "Existing key 3 has the correct value.");
-    $this->assertIdentical($ret['test6']->data, 13, "Existing key 6 has the correct value.");
-    $this->assertIdentical($ret['test7']->data, 17, "Existing key 7 has the correct value.");
+    $this->assertIdentical($ret['test2']->data, 3, "Existing cache id test2 has the correct value.");
+    $this->assertIdentical($ret['test3']->data, 5, "Existing cache id test3 has the correct value.");
+    $this->assertIdentical($ret['test6']->data, 13, "Existing cache id test6 has the correct value.");
+    $this->assertIdentical($ret['test7']->data, 17, "Existing cache id test7 has the correct value.");
 
     // Proceed the test a second time after deleting and setting new keys which
     // ensures no static cache stall.