Rewrite Cookie tests to be runnable and cover current behaviour

The cookie tests were all being skipped because headers are always sent
by the PHPUnit test runner (fixes kohana/kohana#47).

Additionally even when they ran they were covering very little of the actual
logic of the class, mostly just asserting that setcookie returns TRUE. Rewrote
the tests completely and slightly refactored the Cookie class to allow
mocking of the timestamp and setcookie calls.

Refs #547.

classes/Kohana/Cookie.php

@@ -78,7 +78,7 @@ public static function get($key, $default = NULL)
 			}
 
 			// The cookie signature is invalid, delete it
-			Cookie::delete($key);
+			static::delete($key);
 		}
 
 		return $default;
@@ -88,33 +88,38 @@ public static function get($key, $default = NULL)
 	 * Sets a signed cookie. Note that all cookie values must be strings and no
 	 * automatic serialization will be performed!
 	 *
+	 * [!!] By default, Cookie::$expiration is 0 - if you skip/pass NULL for the optional
+	 *      lifetime argument your cookies will expire immediately unless you have separately
+	 *      configured Cookie::$expiration.
+	 *
+	 *
 	 *     // Set the "theme" cookie
 	 *     Cookie::set('theme', 'red');
 	 *
 	 * @param   string  $name       name of cookie
 	 * @param   string  $value      value of cookie
-	 * @param   integer $expiration lifetime in seconds
+	 * @param   integer $lifetime   lifetime in seconds
 	 * @return  boolean
 	 * @uses    Cookie::salt
 	 */
-	public static function set($name, $value, $expiration = NULL)
+	public static function set($name, $value, $lifetime = NULL)
 	{
-		if ($expiration === NULL)
+		if ($lifetime === NULL)
 		{
 			// Use the default expiration
-			$expiration = Cookie::$expiration;
+			$lifetime = Cookie::$expiration;
 		}
 
-		if ($expiration !== 0)
+		if ($lifetime !== 0)
 		{
 			// The expiration is expected to be a UNIX timestamp
-			$expiration += time();
+			$lifetime += static::_time();
 		}
 
 		// Add the salt to the cookie value
 		$value = Cookie::salt($name, $value).'~'.$value;
 
-		return setcookie($name, $value, $expiration, Cookie::$path, Cookie::$domain, Cookie::$secure, Cookie::$httponly);
+		return static::_setcookie($name, $value, $lifetime, Cookie::$path, Cookie::$domain, Cookie::$secure, Cookie::$httponly);
 	}
 
 	/**
@@ -131,16 +136,18 @@ public static function delete($name)
 		unset($_COOKIE[$name]);
 
 		// Nullify the cookie and make it expire
-		return setcookie($name, NULL, -86400, Cookie::$path, Cookie::$domain, Cookie::$secure, Cookie::$httponly);
+		return static::_setcookie($name, NULL, -86400, Cookie::$path, Cookie::$domain, Cookie::$secure, Cookie::$httponly);
 	}
 
 	/**
 	 * Generates a salt string for a cookie based on the name and value.
 	 *
 	 *     $salt = Cookie::salt('theme', 'red');
 	 *
-	 * @param   string  $name   name of cookie
-	 * @param   string  $value  value of cookie
+	 * @param   string $name name of cookie
+	 * @param   string $value value of cookie
+	 *
+	 * @throws Kohana_Exception if Cookie::$salt is not configured
 	 * @return  string
 	 */
 	public static function salt($name, $value)
@@ -157,4 +164,35 @@ public static function salt($name, $value)
 		return sha1($agent.$name.$value.Cookie::$salt);
 	}
 
+	/**
+	 * Proxy for the native setcookie function - to allow mocking in unit tests so that they do not fail when headers
+	 * have been sent.
+	 *
+	 * @param string  $name
+	 * @param string  $value
+	 * @param integer $expire
+	 * @param string  $path
+	 * @param string  $domain
+	 * @param boolean $secure
+	 * @param boolean $httponly
+	 *
+	 * @return bool
+	 * @see setcookie
+	 */
+	protected static function _setcookie($name, $value, $expire, $path, $domain, $secure, $httponly)
+	{
+		return setcookie($name, $value, $expire, $path, $domain, $secure, $httponly);
+	}
+
+	/**
+	 * Proxy for the native time function - to allow mocking of time-related logic in unit tests
+	 *
+	 * @return int
+	 * @see    time
+	 */
+	protected static function _time()
+	{
+		return time();
+	}
+
 }