Implement Countable in MongoGridFSCursor

lib/Mongo/MongoGridFSCursor.php

@@ -17,7 +17,7 @@ if (class_exists('MongoGridFSCursor', false)) {
     return;
 }
 
-class MongoGridFSCursor extends MongoCursor
+class MongoGridFSCursor extends MongoCursor implements Countable
 {
     /**
      * @static

tests/Alcaeus/MongoDbAdapter/Mongo/MongoGridFSCursorTest.php

@@ -3,6 +3,7 @@
 namespace Alcaeus\MongoDbAdapter\Tests\Mongo;
 
 use Alcaeus\MongoDbAdapter\Tests\TestCase;
+use Countable;
 
 class MongoGridFSCursorTest extends TestCase
 {
@@ -37,4 +38,16 @@ class MongoGridFSCursorTest extends TestCase
             ], $value->file);
         }
     }
+
+    public function testInterfaces()
+    {
+        $this->skipTestIf(extension_loaded('mongo'));
+
+        $gridfs = $this->getGridFS();
+        $id = $gridfs->storeBytes('foo', ['filename' => 'foo.txt']);
+        $gridfs->storeBytes('bar', ['filename' => 'bar.txt']);
+
+        $cursor = $gridfs->find(['filename' => 'foo.txt']);
+        $this->assertInstanceOf(Countable::class, $cursor);
+    }
 }