fix risky tests and assert true for silent tests

tests/Spout/Writer/CSV/WriterTest.php

@@ -89,6 +89,7 @@ class WriterTest extends TestCase
         $writer->openToFile($resourcePath);
         $writer->close();
         $writer->close(); // This call should not cause any error
+        $this->assertTrue(true);
     }
 
     /**