diff -u b/core/modules/migrate/tests/src/Unit/MigrateSourceTest.php b/core/modules/migrate/tests/src/Unit/MigrateSourceTest.php
--- b/core/modules/migrate/tests/src/Unit/MigrateSourceTest.php
+++ b/core/modules/migrate/tests/src/Unit/MigrateSourceTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Tests\migrate\Unit;
 
+use Drupal\Core\Cache\CacheBackendInterface;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\migrate\MigrateExecutable;
 use Drupal\migrate\Plugin\MigrateIdMapInterface;
@@ -139,12 +140,12 @@
    * Test that the source count is correct.
    */
   public function testCount() {
-    // Use the Apcu cache backend, which confirms that the cache API is being
-    // properly used.
+    // Mock the cache to validate set() receives appropriate arguments.
     $container = new ContainerBuilder();
-    $cache_tags_checksum = $this->getMock('\Drupal\Core\Cache\CacheTagsChecksumInterface');
-    $container->register('cache.migrate', 'Drupal\Core\Cache\ApcuBackend')
-      ->setArguments(['migrate', 'migrate', $cache_tags_checksum]);
+    $cache = $this->getMock(CacheBackendInterface::class);
+    $cache->expects($this->any())->method('set')
+        ->with($this->isType('string'), $this->isType('int'), $this->isType('int'));
+    $container->set('cache.migrate', $cache);
     \Drupal::setContainer($container);
 
     // Test that the basic count works.