Issue #2492429 by mikeryan, neclimdul: Migration count caching broken

core/modules/migrate/src/Plugin/migrate/source/SourcePluginBase.php

@@ -423,7 +423,7 @@ abstract class SourcePluginBase extends PluginBase implements MigrateSourceInter
     // class to get the count from the source.
     if ($refresh || !$this->cacheCounts) {
       $count = $this->getIterator()->count();
-      $this->getCache()->set($this->cacheKey, $count, 'cache');
+      $this->getCache()->set($this->cacheKey, $count);
     }
     else {
       // Caching is in play, first try to retrieve a cached count.
@@ -436,7 +436,7 @@ abstract class SourcePluginBase extends PluginBase implements MigrateSourceInter
         // No cached count, ask the derived class to count 'em up, and cache
         // the result.
         $count = $this->getIterator()->count();
-        $this->getCache()->set($this->cacheKey, $count, 'cache');
+        $this->getCache()->set($this->cacheKey, $count);
       }
     }
     return $count;

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;
@@ -139,10 +140,12 @@ class MigrateSourceTest extends MigrateTestCase {
    * Test that the source count is correct.
    */
   public function testCount() {
-
+    // Mock the cache to validate set() receives appropriate arguments.
     $container = new ContainerBuilder();
-    $container->register('cache.migrate', 'Drupal\Core\Cache\NullBackend')
-      ->setArguments(['migrate']);
+    $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.