test: add test for filters

Author: kenjis

tests/CI4Twig/TwigTest.php

@@ -110,4 +110,18 @@ public function testFunctionSafe()
         $output = $obj->render('functions_safe');
         $this->assertSame("<s>test</s>\n", $output);
     }
+
+    public function testFilter()
+    {
+        $obj = new Twig(
+            [
+                'paths'   => __DIR__ . '/../templates/',
+                'filters' => ['str_rot13'],
+                'cache'   => false,
+            ]
+        );
+
+        $output = $obj->render('filters');
+        $this->assertSame("PbqrVtavgre Fvzcyr naq Frpher Gjvt\n", $output);
+    }
 }

tests/templates/filters.twig

@@ -0,0 +1 @@
+{{ 'CodeIgniter Simple and Secure Twig'|str_rot13 }}