diff --git a/.gitignore b/.gitignore
index 4eb89f8..2d769b6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 /vendor/
 /.idea
 /tests/error.log
+/.phpunit.result.cache
diff --git a/phpunit.xml b/phpunit.xml
new file mode 100644
index 0000000..e340815
--- /dev/null
+++ b/phpunit.xml
@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<phpunit bootstrap = "vendor/autoload.php"
+         backupGlobals               = "false"
+         backupStaticAttributes      = "false"
+         colors                      = "true"
+         convertErrorsToExceptions   = "true"
+         convertNoticesToExceptions  = "true"
+         convertWarningsToExceptions = "true"
+         processIsolation            = "false"
+         stopOnFailure               = "false"
+         syntaxCheck                 = "false">
+
+    <testsuites>
+        <testsuite name="Project Test Suite">
+            <directory>tests</directory>
+        </testsuite>
+    </testsuites>
+
+    <filter>
+        <whitelist>
+            <directory suffix=".php">src/</directory>
+        </whitelist>
+    </filter>
+
+    <php>
+        <env name="APP_ENV" value="testing"/>
+    </php>
+
+</phpunit>
\ No newline at end of file
diff --git a/src/SRSSBuilder.php b/src/Builder/SRSSBuilder.php
similarity index 76%
rename from src/SRSSBuilder.php
rename to src/Builder/SRSSBuilder.php
index 9d89403..5a6f1ae 100644
--- a/src/SRSSBuilder.php
+++ b/src/Builder/SRSSBuilder.php
@@ -1,16 +1,27 @@
 <?php
 
-namespace Shikiryu\SRSS;
+namespace Shikiryu\SRSS\Builder;
 
 use DOMDocument;
+use DOMElement;
+use Shikiryu\SRSS\Entity\Channel;
+use Shikiryu\SRSS\Entity\Item;
+use Shikiryu\SRSS\Parser\ItemParser;
+use Shikiryu\SRSS\SRSS;
+use Shikiryu\SRSS\SRSSTools;
 
 class SRSSBuilder extends DomDocument
 {
-    public function build()
+    public function build(SRSS $srss, string $filepath)
     {
         $root = $this->createElement('rss');
         $root->setAttribute('version', '2.0');
         $channel = $this->createElement('channel');
+
+        $this->appendChannelToDom($srss->channel, $channel);
+
+        $this->appendItemsToDom($srss->items, $channel);
+
         $root->appendChild($channel);
         $this->appendChild($root);
         $this->encoding = 'UTF-8';
@@ -18,13 +29,16 @@ class SRSSBuilder extends DomDocument
         $this->formatOutput = true;
         $this->preserveWhiteSpace = false;
         // $docs = 'http://www.scriptol.fr/rss/RSS-2.0.html';
+
+        $this->save($filepath);
     }
 
     /**
      * add a SRSS Item as an item into current RSS as first item
-     * @param SRSSItem $item
+     *
+     * @param ItemParser $item
      */
-    public function addItemBefore(SRSSItem $item)
+    public function addItemBefore(ItemParser $item)
     {
         $node = $this->importNode($item->getItem(), true);
         $items =  $this->getElementsByTagName('item');
@@ -41,9 +55,10 @@ class SRSSBuilder extends DomDocument
 
     /**
      * add a SRSS Item as an item into current RSS
-     * @param SRSSItem $item
+     *
+     * @param ItemParser $item
      */
-    public function addItem(SRSSItem $item)
+    public function addItem(ItemParser $item)
     {
         $node = $this->importNode($item->getItem(), true);
         $channel = $this->_getChannel();
@@ -54,7 +69,7 @@ class SRSSBuilder extends DomDocument
      * display XML
      * see DomDocument's docs
      */
-    public function show(): bool|string
+    public function show()
     {
         // TODO build
         return $this->saveXml();
@@ -159,4 +174,29 @@ class SRSSBuilder extends DomDocument
         }
         $this->attr['cloud'] = $array;
     }
+
+    private function appendChannelToDom(Channel $channel, DOMElement $node)
+    {
+        foreach (array_filter($channel->toArray(), fn($el) => !empty($el)) as $name => $value) {
+            $new_node = $this->createElement($name, $value);
+            $node->appendChild($new_node);
+        }
+    }
+
+    private function appendItemsToDom(array $items, DOMElement $channel)
+    {
+        foreach ($items as $item) {
+            $this->appendItemToDom($item, $channel);
+        }
+    }
+
+    private function appendItemToDom(Item $item, DOMElement $channel)
+    {
+        $itemNode = $this->createElement('item');
+        foreach (array_filter($item->toArray()) as $name => $value) {
+            $new_node = $this->createElement($name, $value);
+            $itemNode->appendChild($new_node);
+        }
+        $channel->appendChild($itemNode);
+    }
 }
\ No newline at end of file
diff --git a/src/Entity/Channel.php b/src/Entity/Channel.php
index 9700bad..d4d958f 100644
--- a/src/Entity/Channel.php
+++ b/src/Entity/Channel.php
@@ -16,18 +16,18 @@ class Channel extends HasValidator implements SRSSElement
      * @required
      * @nohtml
      */
-    public string $title;
+    public string $title = '';
 
     /**
      * @required
      * @url
      */
-    public string $link;
+    public string $link = '';
 
     /**
      * @required
      */
-    public string $description;
+    public string $description = '';
 
     /**
      * @lang
@@ -96,9 +96,7 @@ class Channel extends HasValidator implements SRSSElement
      */
     public function isValid(): bool
     {
-        $annotation_validation = new Validator();
-
-        return $annotation_validation->isObjectValid($this);
+        return (new Validator())->isObjectValid($this);
     }
 
     /**
@@ -106,6 +104,8 @@ class Channel extends HasValidator implements SRSSElement
      */
     public function toArray(): array
     {
-        return get_object_vars($this);
+        $vars = get_object_vars($this);
+        unset($vars['validated']);
+        return $vars;
     }
 }
\ No newline at end of file
diff --git a/src/Entity/Channel/Image.php b/src/Entity/Channel/Image.php
index d794078..f4fac3a 100644
--- a/src/Entity/Channel/Image.php
+++ b/src/Entity/Channel/Image.php
@@ -2,14 +2,47 @@
 
 namespace Shikiryu\SRSS\Entity\Channel;
 
-class Image
+use Shikiryu\SRSS\Entity\SRSSElement;
+use Shikiryu\SRSS\Validator\HasValidator;
+use Shikiryu\SRSS\Validator\Validator;
+
+class Image extends HasValidator implements SRSSElement
 {
+    /**
+     * @required
+     * @url
+     */
     public string $url;
+    /**
+     * @required
+     * @nohtml
+     */
     public string $title;
+    /**
+     * @required
+     * @url
+     */
     public string $link;
-    public int $width; // Maximum value for width is 144, default value is 88.
-    public int $height; //Maximum value for height is 400, default value is 31.
+    /**
+     * @int
+     * @max 144
+     */
+    public int $width = 88; // Maximum value for width is 144, default value is 88.
+    /**
+     * @int
+     * @max 400
+     */
+    public int $height = 31; //Maximum value for height is 400, default value is 31.
+
     public string $description;
 
-    public array $required = ['url', 'title', 'link'];
+    public function isValid(): bool
+    {
+        return (new Validator())->isObjectValid($this);
+    }
+
+    public function toArray(): array
+    {
+        return get_object_vars($this);
+    }
 }
\ No newline at end of file
diff --git a/src/Entity/Item.php b/src/Entity/Item.php
index e3cd66b..2831f2f 100644
--- a/src/Entity/Item.php
+++ b/src/Entity/Item.php
@@ -2,33 +2,68 @@
 
 namespace Shikiryu\SRSS\Entity;
 
-class Item implements SRSSElement
+use Shikiryu\SRSS\Validator\HasValidator;
+use Shikiryu\SRSS\Validator\Validator;
+
+/**
+ * https://cyber.harvard.edu/rss/rss.html#hrelementsOfLtitemgt
+ */
+class Item extends HasValidator implements SRSSElement
 {
-    public ?string $title;
-    public ?string $link;
-    public ?string $description;
-    public ?string $author;
-    public ?string $category;
-    public ?string $comments;
-    public ?string $enclosure;
-    public ?string $guid;
-    public ?string $pubDate;
-    public ?string $source;
+    /**
+     * @requiredOr description
+     * @nohtml
+     */
+    public ?string $title = null;
+    /**
+     * @url
+     */
+    public ?string $link = null;
+    /**
+     * @requiredOr title
+     */
+    public ?string $description = null;
+    /**
+     * @email
+     */
+    public ?string $author = null;
+    /*
+     * TODO can be multiple with attributes and all
+     */
+    public ?string $category = null;
+    /**
+     * @url
+     */
+    public ?string $comments = null;
+    /*
+     * TODO 1 attributes and 1 value
+     */
+    public ?string $enclosure = null;
+    public ?string $guid = null;
+    /**
+     * @date
+     */
+    public ?string $pubDate = null;
+    /*
+     * TODO 1 attributes and 1 value
+     */
+    public ?string $source = null;
 
     /**
      * @var \Shikiryu\SRSS\Entity\Media\Content[]
+     * @contentMedia
      */
     public array $medias = [];
 
-    public array $required = ['description'];
-
     public function isValid(): bool
     {
-        return count(array_filter($this->required, fn($field) => !empty($this->{$field}))) === 0;
+        return (new Validator())->isObjectValid($this);
     }
 
     public function toArray(): array
     {
-        return get_object_vars($this);
+        $vars = get_object_vars($this);
+        unset($vars['validated']);
+        return $vars;
     }
 }
\ No newline at end of file
diff --git a/src/Entity/Media/Content.php b/src/Entity/Media/Content.php
index 1e09671..bfbd14a 100644
--- a/src/Entity/Media/Content.php
+++ b/src/Entity/Media/Content.php
@@ -2,123 +2,76 @@
 
 namespace Shikiryu\SRSS\Entity\Media;
 
-use DOMDocument;
-use DOMElement;
-use DOMNode;
-use Shikiryu\SRSS\SRSSException;
-use Shikiryu\SRSS\SRSSTools;
+use Shikiryu\SRSS\Entity\SRSSElement;
+use Shikiryu\SRSS\Validator\HasValidator;
+use Shikiryu\SRSS\Validator\Validator;
 
-class Content extends DomDocument
+class Content extends HasValidator implements SRSSElement
 {
-    protected array $possibilities = [
-        'url'          => 'link',
-        'fileSize'     => 'int', // TODO
-        'type'         => 'media_type', // TODO
-        'medium'       => 'media_medium', // TODO
-        'isDefault'    => 'bool', // TODO
-        'expression'   => 'medium_expression', // TODO
-        'bitrate'      => 'int',
-        'framerate'    => 'int',
-        'samplingrate' => 'float',
-        'channels'     => 'int',
-        'duration'     => 'int',
-        'height'       => 'int',
-        'width'        => 'int',
-        'lang'         => '',
-    ];
-    private array $attr = [];
-
-    private DOMNode $node;
-
     /**
-     * Constructor
-     *
-     * @param DomNode $node
+     * @url
      */
-    public function __construct(?\DOMNode $node = null)
+    public ?string $url = null;
+    /**
+     * @int
+     */
+    public ?int $filesize = null;
+    /**
+     * @mediaType
+     */
+    public ?string $type = null;
+    /**
+     * @mediaMedium
+     */
+    public ?string $medium = null;
+    /**
+     * @bool
+     */
+    public ?bool $isDefault = null;
+    /**
+     * @mediaExpression
+     */
+    public ?string $expression = null;
+    /**
+     * @int
+     */
+    public ?int $bitrate = null;
+    /**
+     * @int
+     */
+    public ?int $framerate = null;
+    /**
+     * @float
+     */
+    public ?float $samplerate = null;
+    /**
+     * @int
+     */
+    public ?int $channels = null;
+    /**
+     * @int
+     */
+    public ?int $duration = null;
+    /**
+     * @int
+     */
+    public ?int $height = null;
+    /**
+     * @int
+     */
+    public ?int $width = null;
+    /**
+     * @lang
+     */
+    public ?string $lang = null;
+
+    public function isValid(): bool
     {
-        parent::__construct();
-        if ($node instanceof DOMElement) {
-            $this->node = $this->importNode($node, true);
-        } else {
-            $this->node = $this->importNode(new DomElement('item'));
-        }
-        $this->_loadAttributes();
+        return (new Validator())->isObjectValid($this);
     }
 
-    /**
-     * @return void
-     */
-    private function _loadAttributes(): void
+    public function toArray(): array
     {
-        foreach ($this->node->attributes as $attributes) {
-            if (array_key_exists($attributes->name, $this->possibilities)) {
-                $this->{$attributes->name} = $attributes->value;
-            }
-        }
-    }
-
-    /**
-     * main getter for properties
-     *
-     * @param $name
-     *
-     * @return null|string
-     * @throws SRSSException
-     */
-    public function __get($name)
-    {
-        if (array_key_exists($name, $this->attr)) {
-            return $this->attr[$name];
-        }
-
-        if (array_key_exists($name, $this->possibilities)) {
-            $tmp = $this->node->getElementsByTagName($name);
-            if ($tmp->length !== 1) {
-                return null;
-            }
-
-            return $tmp->item(0)->nodeValue;
-        }
-
-        throw new SRSSException(sprintf('%s is not a possible item (%s)', $name, implode(', ', array_keys($this->possibilities))));
-    }
-
-    /**
-     * @param $name
-     *
-     * @return bool
-     */
-    public function __isset($name)
-    {
-        return isset($this->attr[$name]);
-    }
-
-    /**
-     * main setter for properties
-     *
-     * @param $name
-     * @param $val
-     *
-     * @throws SRSSException
-     */
-    public function __set($name, $val)
-    {
-        if (!array_key_exists($name, $this->possibilities)) {
-            throw new SRSSException(sprintf('%s is not a possible item (%s)', $name, implode(', ', array_keys($this->possibilities))));
-        }
-
-        $flag = $this->possibilities[$name];
-
-        if ($flag !== '') {
-            $val = SRSSTools::check($val, $flag);
-        }
-
-        if (!empty($val)) {
-            if ($this->$name === null) {
-                $this->node->appendChild(new DomElement($name, $val));
-            }
-            $this->attr[$name] = $val;
-        }
+        return get_object_vars($this);
     }
 }
\ No newline at end of file
diff --git a/src/Entity/Media/Group.php b/src/Entity/Media/Group.php
deleted file mode 100644
index 64ca71c..0000000
--- a/src/Entity/Media/Group.php
+++ /dev/null
@@ -1,8 +0,0 @@
-<?php
-
-namespace Shikiryu\SRSS\Entity\Media;
-
-class Group
-{
-
-}
\ No newline at end of file
diff --git a/src/SRSSException.php b/src/Exception/SRSSException.php
similarity index 90%
rename from src/SRSSException.php
rename to src/Exception/SRSSException.php
index eca3cc8..fd35775 100644
--- a/src/SRSSException.php
+++ b/src/Exception/SRSSException.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Shikiryu\SRSS;
+namespace Shikiryu\SRSS\Exception;
 
 use Exception;
 
diff --git a/src/SRSSItem.php b/src/Parser/ItemParser.php
similarity index 89%
rename from src/SRSSItem.php
rename to src/Parser/ItemParser.php
index 4c52bd5..f65649c 100644
--- a/src/SRSSItem.php
+++ b/src/Parser/ItemParser.php
@@ -1,18 +1,19 @@
 <?php
 
-namespace Shikiryu\SRSS;
+namespace Shikiryu\SRSS\Parser;
 
 use DOMDocument;
 use DOMElement;
 use DOMException;
 use DOMNode;
 use Shikiryu\SRSS\Entity\Item;
-use Shikiryu\SRSS\Entity\Media\Content;
+use Shikiryu\SRSS\Exception\SRSSException;
+use Shikiryu\SRSS\SRSSTools;
 
 /**
  * @property string|null $description
  */
-class SRSSItem extends DomDocument
+class ItemParser extends DomDocument
 {
 
     protected DOMNode $node; // item node
@@ -42,9 +43,6 @@ class SRSSItem extends DomDocument
     public function __construct($node = null)
     {
         parent::__construct();
-//        if ($node instanceof DOMElement) $this->node = $this->importNode($node, true);
-//        else $this->node = $this->importNode(new DomElement('item'));
-//        $this->_loadAttributes();
     }
 
     /**
@@ -60,9 +58,9 @@ class SRSSItem extends DomDocument
                 if (array_key_exists($child->nodeName, self::$possibilities) && self::$possibilities[$child->nodeName] === 'folder') {
                     self::_loadChildAttributes($item, $child);
                 } elseif  ($child->nodeName === 'media:content') {
-                    $item->medias[] = new Content($child);
+                    $item->medias[] = MediaContentParser::read($child);
                 } else {
-                    $item->{$child->nodeName} = $child->nodeValue;
+                    $item->{$child->nodeName} = trim($child->nodeValue);
                 }
             }
         }
@@ -188,15 +186,6 @@ class SRSSItem extends DomDocument
         throw new SRSSException(sprintf('%s is not a possible item (%s)', $name, implode(', ', array_keys($this->possibilities))));
     }
 
-    /**
-     * display item's XML
-     * see DomDocument's docs
-     */
-    public function show()
-    {
-        return $this->saveXml();
-    }
-
     /**
      * transform current item's object into an array
      * @return array
diff --git a/src/Parser/MediaContentParser.php b/src/Parser/MediaContentParser.php
new file mode 100644
index 0000000..4896cf5
--- /dev/null
+++ b/src/Parser/MediaContentParser.php
@@ -0,0 +1,79 @@
+<?php
+
+namespace Shikiryu\SRSS\Parser;
+
+use DOMDocument;
+use DOMElement;
+use DOMException;
+use DOMNode;
+use Shikiryu\SRSS\Entity\Item;
+use Shikiryu\SRSS\Entity\Media\Content;
+use Shikiryu\SRSS\Exception\SRSSException;
+use Shikiryu\SRSS\SRSSTools;
+
+/**
+ * @property string|null $description
+ */
+class MediaContentParser extends DomDocument
+{
+    protected DOMNode $node; // item node
+    protected $attr; // item's properties
+
+    // possible properties' names
+    protected static $possibilities = [
+        'title'         => 'nohtml',
+        'link'          => 'link',
+        'description'   => 'html',
+        'author'        => 'email',
+        'category'      => 'nohtml',
+        'comments'      => 'link',
+        'enclosure'     => '',
+        'guid'          => 'nohtml',
+        'pubDate'       => 'date',
+        'source'        => 'link',
+        'media:group'   => 'folder',
+        'media:content' => '',
+    ];
+
+    /**
+     * Constructor
+     *
+     * @param DomNode $node
+     */
+    public function __construct($node = null)
+    {
+        parent::__construct();
+    }
+
+    /**
+     * @param Content $item
+     * @param $nodes
+     *
+     * @return void
+     */
+    private static function _loadChildAttributes(Content $item, $nodes): void
+    {
+        foreach ($nodes->attributes as $attribute) {
+
+            if (property_exists(Content::class, $attribute->name)) {
+                $item->{$attribute->name} = $attribute->value;
+            }
+
+        }
+    }
+
+    /**
+     * @param DOMNode|null $node
+     *
+     * @return Content
+     */
+    public static function read(?DOMNode $node = null): Content
+    {
+        $content = new Content();
+        if ($node instanceof DOMNode) {
+            self::_loadChildAttributes($content, $node);
+        }
+
+        return $content;
+    }
+}
\ No newline at end of file
diff --git a/src/SRSSParser.php b/src/Parser/SRSSParser.php
similarity index 92%
rename from src/SRSSParser.php
rename to src/Parser/SRSSParser.php
index 70e5a04..a7f9076 100644
--- a/src/SRSSParser.php
+++ b/src/Parser/SRSSParser.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Shikiryu\SRSS;
+namespace Shikiryu\SRSS\Parser;
 
 use DOMDocument;
 use DOMNodeList;
@@ -8,6 +8,8 @@ use DOMXPath;
 use Shikiryu\SRSS\Entity\Channel;
 use Shikiryu\SRSS\Entity\Channel\Image;
 use Shikiryu\SRSS\Entity\Item;
+use Shikiryu\SRSS\Exception\SRSSException;
+use Shikiryu\SRSS\SRSS;
 
 class SRSSParser extends DomDocument
 {
@@ -38,7 +40,7 @@ class SRSSParser extends DomDocument
      * @param string $link
      *
      * @return \Shikiryu\SRSS\SRSS
-     * @throws \Shikiryu\SRSS\SRSSException
+     * @throws \Shikiryu\SRSS\Exception\SRSSException
      */
     public function parse(string $link)
     {
@@ -59,9 +61,9 @@ class SRSSParser extends DomDocument
 
     /**
      * @return Item[]
-     * @throws \Shikiryu\SRSS\SRSSException
+     * @throws \Shikiryu\SRSS\Exception\SRSSException
      */
-    private function getItems(): mixed
+    private function getItems(): array
     {
         $channel = $this->_getChannel();
         /** @var DOMNodeList $items */
@@ -70,7 +72,7 @@ class SRSSParser extends DomDocument
         $this->doc->items = [];
         if ($length > 0) {
             for($i = 0; $i < $length; $i++) {
-                $this->doc->items[$i] = SRSSItem::read($items->item($i));
+                $this->doc->items[$i] = ItemParser::read($items->item($i));
             }
         }
 
diff --git a/src/SRSS.php b/src/SRSS.php
index 954f5bb..4eb353d 100644
--- a/src/SRSS.php
+++ b/src/SRSS.php
@@ -5,38 +5,17 @@ namespace Shikiryu\SRSS;
 use Iterator;
 use Shikiryu\SRSS\Entity\Channel;
 use Shikiryu\SRSS\Entity\Item;
+use Shikiryu\SRSS\Exception\SRSSException;
+use Shikiryu\SRSS\Parser\SRSSParser;
 
 class SRSS implements Iterator
 {
     public Channel $channel;
+    /** @var Item[] */
     public array $items; // array of SRSSItems
 
     private int $position; // Iterator position
 
-    // lists of possible attributes for RSS
-    protected $possibleAttr = [
-        'title'          => 'nohtml',
-        'link'           => 'link',
-        'description'    => 'html',
-        'language'       => '',
-        //'language'			=> 'lang',
-        'copyright'      => 'nohtml',
-        'pubDate'        => 'date',
-        'lastBuildDate'  => 'date',
-        'category'       => 'nohtml',
-        'docs'           => 'link',
-        'cloud'          => '',
-        'generator'      => 'nohtml',
-        'managingEditor' => 'email',
-        'webMaster'      => 'email',
-        'ttl'            => 'int',
-        'image'          => '',
-        'rating'         => 'nohtml',
-        //'textInput'			=> '',
-        'skipHours'      => 'hour',
-        'skipDays'       => 'day',
-    ];
-
     /**
      * Constructor
      */
@@ -78,15 +57,10 @@ class SRSS implements Iterator
     public function isValid(): bool
     {
         $valid = true;
-        $items = $this->getItems();
-        $invalidItems = [];
-        $i = 1;
-        foreach ($items as $item) {
+        foreach ($this->getItems() as $item) {
             if ($item->isValid() === false) {
-                $invalidItems[] = $i;
                 $valid = false;
             }
-            $i++;
         }
 
         return ($valid && $this->channel->isValid());
@@ -115,11 +89,10 @@ class SRSS implements Iterator
         if (!property_exists(Channel::class, $name)) {
             throw new SRSSException($name . ' is not a possible item');
         }
-        $flag = $this->possibleAttr[$name];
-        $val = SRSSTools::check($val, $flag);
-        if (!empty($val)) {
+        // TODO add validator ?
+//        if ((new Validator())->isPropertyValid($this->channel, $name)) {
             $this->channel->{$name} = $val;
-        }
+//        }
     }
 
     /**
@@ -231,4 +204,9 @@ class SRSS implements Iterator
 
         return $doc;
     }
+
+    public function addItem(Item $rssItem)
+    {
+        $this->items[] = $rssItem;
+    }
 }
diff --git a/src/SRSSTools.php b/src/SRSSTools.php
index e7d42a4..9d7ee3e 100644
--- a/src/SRSSTools.php
+++ b/src/SRSSTools.php
@@ -2,9 +2,11 @@
 
 namespace Shikiryu\SRSS;
 
+use DateTimeInterface;
+
 class SRSSTools
 {
-    public static function check($check, $flag)
+    /*public static function check($check, $flag)
     {
         return match ($flag) {
             'nohtml' => self::noHTML($check),
@@ -19,11 +21,9 @@ class SRSSTools
             'media_type' => self::checkMediaType($check),
             'media_medium' => self::checkMediaMedium($check),
             'bool' => self::checkBool($check),
-            'medium_expression' => self::checkMediumExpression($check),
-            '' => $check,
-            default => throw new SRSSException('flag ' . $flag . ' does not exist.'),
+            'medium_expression' => self::checkMediumExpression($check)
         };
-    }
+    }*/
 
     /**
      * format the RSS to the wanted format
@@ -61,6 +61,10 @@ class SRSSTools
             return date("D, d M Y H:i:s T", strtotime($date));
         }
 
+        if (count(explode(' ', $date)) === 2) {
+            return \DateTime::createFromFormat('Y-m-d H:i:s', $date)->format(DateTimeInterface::RSS);
+        }
+
         [$j, $m, $a] = explode('/', $date);
 
         return date("D, d M Y H:i:s T", strtotime($a.'-'.$m.'-'.$j));
diff --git a/src/Validator/Validator.php b/src/Validator/Validator.php
index 2161006..c16f1de 100644
--- a/src/Validator/Validator.php
+++ b/src/Validator/Validator.php
@@ -5,9 +5,36 @@ namespace Shikiryu\SRSS\Validator;
 use DateTimeInterface;
 use ReflectionClass;
 use ReflectionException;
+use ReflectionProperty;
+use Shikiryu\SRSS\Entity\Media\Content;
 
 class Validator
 {
+    protected ?object $object = null;
+    /**
+     * @throws \ReflectionException
+     */
+    public function isPropertyValid($object, $property)
+    {
+        $properties = array_filter($this->_getClassProperties(get_class($object)), fn($p) => $p->getName() === $property);
+        if (count($properties) !== 1) {
+            return false;
+        }
+
+        $properties = current($properties);
+        $propertyValue = $object->{$properties->name};
+        $propertyAnnotations = $this->_getPropertyAnnotations($properties);
+
+        if (!in_array('required', $propertyAnnotations, true) && empty($propertyValue)) {
+            return true;
+        }
+
+        foreach ($propertyAnnotations as $propertyAnnotation) {
+            $annotation = explode(' ', $propertyAnnotation);
+
+            $object->validated[$properties->name] = $this->_validateProperty($annotation, $propertyValue);
+        }
+    }
 
     /**
      * @throws ReflectionException
@@ -18,7 +45,7 @@ class Validator
             $object = $this->validateObject($object);
         }
 
-        return !in_array(false, $object->validated);
+        return !in_array(false, $object->validated, true);
     }
 
     /**
@@ -26,20 +53,25 @@ class Validator
      */
     public function validateObject($object)
     {
+        $this->object = $object;
         $properties = $this->_getClassProperties(get_class($object));
+        $properties = array_map(fn($property) => array_merge(
+            ['name' => $property->name],
+            ['rules' => $this->_getPropertyAnnotations($property)]
+        ), $properties);
 
         foreach ($properties as $property) {
-            $propertyValue = $object->{$property->name};
-            $propertyAnnotations = $this->_getPropertyAnnotations($property, get_class($object));
+            $propertyValue = $object->{$property['name']};
+//            $propertyAnnotations = $this->_getPropertyAnnotations($property, get_class($object));
 
-            if (!in_array('required', $propertyAnnotations) && empty($propertyValue)) {
+            if (!in_array('required', $property['rules'], true) && empty($propertyValue)) {
                 continue;
             }
 
-            foreach ($propertyAnnotations as $propertyAnnotation) {
+            foreach ($property['rules'] as $propertyAnnotation) {
                 $annotation = explode(' ', $propertyAnnotation);
 
-                $object->validated[$property->name] = $this->_validateProperty($annotation, $propertyValue);
+                $object->validated[$property['name']] = $this->_validateProperty($annotation, $propertyValue);
             }
         }
 
@@ -48,24 +80,29 @@ class Validator
 
     private function _validateProperty(array $annotation, $property): bool
     {
-        if (count($annotation) === 1) {
-            return call_user_func([$this, sprintf('_validate%s', ucfirst($annotation[0]))], $property);
+        if ($annotation[0] === 'var') {
+            return true;
         }
 
-        return true; // TODO check
+        if (count($annotation) === 1) {
+            return $this->{sprintf('_validate%s', ucfirst($annotation[0]))}($property);
+        }
+
+        $args_annotation = array_splice($annotation, 1);
+
+        return $this->{sprintf('_validate%s', ucfirst($annotation[0]))}($property, ...$args_annotation);
     }
 
     /**
+     * @return ReflectionProperty[]
      * @throws ReflectionException
      */
     private function _getClassProperties($class): array
     {
-        $ReflectionClass = new ReflectionClass($class);
-
-        return $ReflectionClass->getProperties();
+        return (new ReflectionClass($class))->getProperties();
     }
 
-    private function _getPropertyAnnotations($property, $className): array
+    private function _getPropertyAnnotations(ReflectionProperty $property): array
     {
         preg_match_all('#@(.*?)\n#s', $property->getDocComment(), $annotations);
 
@@ -87,6 +124,21 @@ class Validator
         return !empty(trim($value));
     }
 
+    private function _validateRequiredOr($value, $other_values): bool
+    {
+        if (!empty($value)) {
+            return true;
+        }
+
+        foreach ($other_values as $other_value) {
+            if (!empty($this->object->$other_value)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     /**
      * @param $value
      * @return bool
@@ -143,4 +195,36 @@ class Validator
             ['monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday', 'sunday']
         );
     }
+
+    private function _validateContentMedia($value)
+    {
+        if (is_array($value)) {
+            foreach ($value as $content) {
+                if (!$content->isValid()) {
+                    return false;
+                }
+            }
+            return true;
+        }
+
+        if ($value instanceof Content) {
+            return $value->isValid();
+        }
+
+        return  false;
+    }
+
+    private function _validateMediaType($value): bool
+    {
+        return true;
+    }
+    private function _validateMediaMedium($value): bool
+    {
+        return in_array($value, ['image', 'audio', 'video', 'document', 'executable']);
+    }
+
+    private function _validateMediaExpression($value): bool
+    {
+        return in_array($value, ['sample', 'full', 'nonstop']);
+    }
 }
\ No newline at end of file
diff --git a/tests/BasicBuilderTest.php b/tests/BasicBuilderTest.php
new file mode 100644
index 0000000..d3be8ed
--- /dev/null
+++ b/tests/BasicBuilderTest.php
@@ -0,0 +1,40 @@
+<?php
+
+use PHPUnit\Framework\TestCase;
+use Shikiryu\SRSS\Builder\SRSSBuilder;
+use Shikiryu\SRSS\Entity\Item;
+use Shikiryu\SRSS\SRSS;
+use Shikiryu\SRSS\SRSSTools;
+
+class BasicBuilderTest extends TestCase
+{
+    public function testCreateBasicRSS()
+    {
+        $srss = SRSS::create();
+        $srss->title = 'My Blog';
+        $srss->description = 'is the best';
+        $srss->link = 'http://shikiryu.com/devblog/';
+        $items = [
+            ['title' => 'title 1', 'link' => 'http://shikiryu.com/devblog/article-1', 'pubDate' => SRSSTools::getRSSDate('2012-03-05 12:02:01'), 'description' => 'description 1'],
+            ['title' => 'title 2', 'link' => 'http://shikiryu.com/devblog/article-2', 'pubDate' => SRSSTools::getRSSDate('2022-03-05 22:02:02'), 'description' => 'description 2'],
+            ['title' => 'title 3', 'link' => 'http://shikiryu.com/devblog/article-3', 'pubDate' => SRSSTools::getRSSDate('2032-03-05 32:02:03'), 'description' => 'description 3'],
+            ['title' => 'title 4', 'link' => 'http://shikiryu.com/devblog/article-4', 'pubDate' => SRSSTools::getRSSDate('2042-03-05 42:02:04'), 'description' => 'description 4'],
+        ];
+        foreach ($items as $item) {
+            $rssItem = new Item();
+            $rssItem->title = $item['title'];
+            $rssItem->link = $item['link'];
+            $rssItem->pubDate = $item['pubDate'];
+            $rssItem->description = $item['description'];
+            $srss->addItem($rssItem);
+        }
+
+        self::assertTrue($srss->isValid());
+
+        $filepath = __DIR__.'/resources/tmp/build/testCreateBasicRSS.rss';
+        $builder = new SRSSBuilder();
+        $builder->build($srss, $filepath);
+
+        self::assertFileExists($filepath);
+    }
+}
\ No newline at end of file
diff --git a/tests/BasicReader.php b/tests/BasicReaderTest.php
similarity index 90%
rename from tests/BasicReader.php
rename to tests/BasicReaderTest.php
index 8e4834e..331ecde 100644
--- a/tests/BasicReader.php
+++ b/tests/BasicReaderTest.php
@@ -1,10 +1,10 @@
 <?php
 
 use PHPUnit\Framework\TestCase;
+use Shikiryu\SRSS\Exception\SRSSException;
 use Shikiryu\SRSS\SRSS;
-use Shikiryu\SRSS\SRSSException;
 
-class BasicReader extends TestCase
+class BasicReaderTest extends TestCase
 {
     public function testReadBasicRSS()
     {
@@ -14,7 +14,7 @@ class BasicReader extends TestCase
         self::assertNotNull($first_item);
         self::assertEquals('RSS Tutorial', $first_item->title);
 
-        self::assertTrue($rss->channel->isValid());
+        self::assertTrue($rss->isValid());
     }
 
     public function testRssNotFound()
@@ -41,6 +41,6 @@ class BasicReader extends TestCase
         self::assertEquals('http://liftoff.msfc.nasa.gov/news/2003/news-laundry.asp', $rss->getLast()->link);
         self::assertEquals('Fri, 30 May 2003 11:06:42 GMT', $rss->getItem(2)->pubDate);
 
-        self::assertTrue($rss->channel->isValid());
+        self::assertTrue($rss->isValid());
     }
 }
\ No newline at end of file
diff --git a/tests/MediaTest.php b/tests/MediaTest.php
index 67511d0..0e88c10 100644
--- a/tests/MediaTest.php
+++ b/tests/MediaTest.php
@@ -7,25 +7,25 @@ class MediaTest extends TestCase
 {
     public function testImages()
     {
-        $rss = SRSS::read('resources/media/cnn.xml');
+        $rss = SRSS::read(__DIR__.'/resources/media/cnn.xml');
         self::assertEquals('CNN.com - RSS Channel - Entertainment', $rss->title);
 
         $first_item = $rss->getFirst();
         self::assertEquals('Kirstie Alley, \'Cheers\' and \'Veronica\'s Closet\' star, dead at 71', $first_item->title);
 
         self::assertEquals('https://cdn.cnn.com/cnnnext/dam/assets/221205172141-kirstie-alley-2005-super-169.jpg', $first_item->medias[0]->url);
-        self::assertTrue($rss->channel->isValid(), var_export($rss->channel->validated, true));
+        self::assertTrue($rss->isValid(), var_export($rss->channel->validated, true));
     }
 
     public function testMusicVideo()
     {
-        $rss = SRSS::read('resources/media/music-video.xml');
+        $rss = SRSS::read(__DIR__.'/resources/media/music-video.xml');
         self::assertEquals('Music Videos 101', $rss->title);
 
         self::assertCount(1, $rss->items);
 
         $first_item = $rss->getFirst();
         self::assertEquals('http://www.foo.com/movie.mov', $first_item->medias[0]->url);
-        self::assertTrue($rss->channel->isValid());
+        self::assertTrue($rss->isValid());
     }
 }
\ No newline at end of file