diff --git a/panda.php b/panda.php
index 13a6412..7357491 100644
--- a/panda.php
+++ b/panda.php
@@ -104,6 +104,17 @@ public function signed_params($verb, $request_path, $params = array(), $timestam
     }
     
     public static function signature_generator($verb, $request_path, $host, $secret_key, $params = array()) {
+        $string_to_sign = self::string_to_sign($verb, $request_path, $host, $params);
+        $context = hash_init('sha256', HASH_HMAC, $secret_key);
+        hash_update($context, $string_to_sign);
+        return base64_encode(hash_final($context, true));
+    }
+    
+    public function generate_signature($verb, $request_path, $params = array()) {
+        return self::signature_generator($verb, $request_path, $this->api_host, $this->secret_key, $params);
+    }
+    
+    public function string_to_sign($verb, $request_path, $host, $params = array()) {
         $request_path = self::canonical_path($request_path);
         $query_string = self::canonical_querystring($params);
         $_verb = strtoupper($verb);
@@ -114,13 +125,7 @@ public static function signature_generator($verb, $request_path, $host, $secret_
 $request_path
 $query_string
 END;
-        $context = hash_init('sha256', HASH_HMAC, $secret_key);
-        hash_update($context, $string_to_sign);
-        return base64_encode(hash_final($context, true));
-    }
-    
-    public function generate_signature($verb, $request_path, $params = array()) {
-        return self::signature_generator($verb, $request_path, $this->api_host, $this->secret_key, $params);
+        return $string_to_sign;
     }
     
     //
diff --git a/test/index.php b/test/index.php
index d7ed0dc..5c8e9b7 100644
--- a/test/index.php
+++ b/test/index.php
@@ -31,7 +31,7 @@ function test_api_host_and_port() {
 }
 
 class SignatureTest extends UnitTestCase {
-    function test_0() {
+    function test_generator_simple() {
         $signature = Panda::signature_generator(
             'GET',
             '/videos.json',
@@ -41,8 +41,8 @@ function test_0() {
         );
         $this->assertEqual('RZml1S8BcxSTCaTSQVnXj/7QA0vM4M6FqRIUuntTYjk=', $signature);
     }
-
-    function test_1() {
+    
+    function test_generator_complex() {
         $signature = Panda::signature_generator(
             'POST',
             '/videos.json',
@@ -56,4 +56,25 @@ function test_1() {
         );
         $this->assertEqual('JKBd6ARhTYqxGeTsqfrPUoOHrvmmz59bkJK37XvrL/U=', $signature);
     }
-}
\ No newline at end of file
+    
+    function test_string_to_sign() {
+        $expected =<<<EOF
+POST
+api.eu.pandastream.com
+/videos.json
+access_key=9c264aba-8d97-df11-b01b-12313c0091c1&cloud_id=5385adf38f3e39de1ddcf4c1b81ad056&timestamp=2010-07-16T06%3A27%3A54%2B00%3A00&upload_redirect_url=http%3A%2F%2Flocalhost%3A44444%2Fpanda%2Fsimplest%2Fplayer.php%3Fpanda_video_id%3D%24id
+EOF;
+        $actual = Panda::string_to_sign(
+            'POST',
+            '/videos.json',
+            'api.eu.pandastream.com',
+            array(
+                'upload_redirect_url' => 'http://localhost:44444/panda/simplest/player.php?panda_video_id=$id',
+                'cloud_id' => '5385adf38f3e39de1ddcf4c1b81ad056',
+                'access_key' => '9c264aba-8d97-df11-b01b-12313c0091c1',
+                'timestamp' => '2010-07-16T06:27:54+00:00',
+            )
+        );
+        $this->assertEqual($expected, $actual);
+    }
+}