diff --git a/src/Component/Collection.php b/src/Component/Collection.php
index 2bcadf3..2b74de2 100644
--- a/src/Component/Collection.php
+++ b/src/Component/Collection.php
@@ -70,7 +70,7 @@ public function get(string $name, $default = null)
     public function add($name, $value)
     {
         if (isset($this[$name])) {
-            return null;
+            return $this;
         }
 
         $this[$name] = $value;
@@ -85,7 +85,9 @@ public function add($name, $value)
      */
     public function set($name, $value)
     {
-        return $this[$name] = $value;
+        $this[$name] = $value;
+
+        return $this;
     }
 
     /**
diff --git a/src/Cookies.php b/src/Cookies.php
index 2dab59d..6c24501 100644
--- a/src/Cookies.php
+++ b/src/Cookies.php
@@ -64,6 +64,20 @@ public function set($name, $value): self
         return $this;
     }
 
+    /**
+     * @param string $name
+     * @param mixed $value
+     * @return self
+     */
+    public function add($name, $value): self
+    {
+        if (!\is_array($value)) {
+            $value = ['value' => (string)$value];
+        }
+
+        return parent::add($name, \array_replace($this->defaults, $value));
+    }
+
     /**
      * Convert to `Set-Cookie` headers
      * @return string[]
@@ -72,7 +86,7 @@ public function toHeaders(): array
     {
         $headers = [];
         foreach ($this as $name => $properties) {
-            $headers[] = $this->toHeader($name, $properties);
+            $headers[] = $this->toHeaderLine($name, $properties);
         }
 
         return $headers;
@@ -84,7 +98,7 @@ public function toHeaders(): array
      * @param  array $properties Cookie properties
      * @return string
      */
-    protected function toHeader(string $name, array $properties): string
+    protected function toHeaderLine(string $name, array $properties): string
     {
         $result = \urlencode($name) . '=' . \urlencode($properties['value']);
 
diff --git a/src/Headers.php b/src/Headers.php
index fffde45..0e12e98 100644
--- a/src/Headers.php
+++ b/src/Headers.php
@@ -113,7 +113,10 @@ public function add($key, $value)
             return $this;
         }
 
-        return parent::add($this->normalizeKey($key), $value);
+        return parent::add($this->normalizeKey($key), [
+            'value' => (array)$value,
+            'originalKey' => $key
+        ]);
     }
 
     /**
@@ -136,12 +139,12 @@ public function remove($key)
      * @param string $key
      * @return bool|string
      */
-    public function normalizeKey($key)
+    public function normalizeKey(string $key)
     {
-        $key = str_replace('_', '-', strtolower($key));
+        $key = \str_replace('_', '-', \strtolower($key));
 
-        if (strpos($key, 'Http-') === 0) {
-            $key = substr($key, 5);
+        if (\strpos($key, 'Http-') === 0) {
+            $key = \substr($key, 5);
         }
 
         return $key;
@@ -157,12 +160,12 @@ public function getAcceptLanguages(): array
         $ls = [];
 
         if ($value = $this->getLine('Accept-Language')) {
-            if (strpos($value, ';')) {
-                list($value,) = explode(';', $value, 2);
+            if (\strpos($value, ';')) {
+                list($value,) = \explode(';', $value, 2);
             }
 
-            $value = str_replace(' ', '', $value);
-            $ls = explode(',', $value);
+            $value = \str_replace(' ', '', $value);
+            $ls = \explode(',', $value);
         }
 
         return $ls;
@@ -178,32 +181,32 @@ public function getAcceptEncodes(): array
         $ens = [];
 
         if ($value = $this->getLine('Accept-Encoding')) {
-            if (strpos($value, ';')) {
-                list($value,) = explode(';', $value, 2);
+            if (\strpos($value, ';')) {
+                list($value,) = \explode(';', $value, 2);
             }
 
-            $value = str_replace(' ', '', $value);
-            $ens = explode(',', $value);
+            $value = \str_replace(' ', '', $value);
+            $ens = \explode(',', $value);
         }
 
         return $ens;
     }
 
     /**
-     * @param bool $toString
-     * @return array
+     * @param bool $join to String
+     * @return array|string
      */
-    public function toHeaderLines(bool $toString = false): array
+    public function toHeaderLines(bool $join = false)
     {
         $output = [];
 
         foreach ($this as $name => $info) {
-            $name = ucwords($name, '-');
-            $value = implode(',', $info['value']);
+            $name = \ucwords($name, '-');
+            $value = \implode(',', $info['value']);
             $output[] = "$name: $value\r\n";
         }
 
-        return $toString ? implode('', $output) : $output;
+        return $join ? \implode('', $output) : $output;
     }
 
     /**
@@ -214,8 +217,8 @@ public function getLines(): array
         $output = [];
 
         foreach ($this as $name => $info) {
-            $name = ucwords($name, '-');
-            $output[$name] = implode(',', $info['value']);
+            $name = \ucwords($name, '-');
+            $output[$name] = \implode(',', $info['value']);
         }
 
         return $output;
diff --git a/src/Response.php b/src/Response.php
index 7054fd5..df9f4cf 100644
--- a/src/Response.php
+++ b/src/Response.php
@@ -365,6 +365,10 @@ public function getStatusCode(): int
      */
     public function getReasonPhrase(): string
     {
+        if ($this->reasonPhrase === null && ($code = $this->status)) {
+            $this->reasonPhrase = self::$messages[$code] ?? '';
+        }
+
         return $this->reasonPhrase;
     }
 
diff --git a/src/ServerRequest.php b/src/ServerRequest.php
index 56efd44..2310817 100644
--- a/src/ServerRequest.php
+++ b/src/ServerRequest.php
@@ -667,7 +667,7 @@ public function withAttribute($name, $value)
      * @param array $attributes
      * @return ServerRequest
      */
-    public function withAttributes(array $attributes): ServerRequest
+    public function withAttributes(array $attributes): self
     {
         $clone = clone $this;
         $clone->attributes = new Collection($attributes);
diff --git a/src/Traits/RequestTrait.php b/src/Traits/RequestTrait.php
index 8034a14..dc2d51d 100644
--- a/src/Traits/RequestTrait.php
+++ b/src/Traits/RequestTrait.php
@@ -174,7 +174,12 @@ public function isMethod($method): bool
         return $this->getMethod() === strtoupper($method);
     }
 
-    public function withMethod($method): RequestTrait
+    /**
+     * @param $method
+     * @return RequestTrait
+     * @throws \InvalidArgumentException
+     */
+    public function withMethod($method): self
     {
         $method = (string)$this->filterMethod($method);
 
diff --git a/test/ResponseTest.php b/test/ResponseTest.php
new file mode 100644
index 0000000..c3c16af
--- /dev/null
+++ b/test/ResponseTest.php
@@ -0,0 +1,29 @@
+<?php
+/**
+ * Created by PhpStorm.
+ * User: Inhere
+ * Date: 2018/3/28 0028
+ * Time: 22:05
+ */
+
+namespace Inhere\Http\Test;
+
+use Inhere\Http\Response;
+use PHPUnit\Framework\TestCase;
+use Psr\Http\Message\ResponseInterface;
+
+/**
+ * Class ResponseTest
+ * @package Inhere\Http\Test
+ */
+class ResponseTest extends TestCase
+{
+    public function testClass()
+    {
+        $res = new Response();
+
+        $this->assertInstanceOf(ResponseInterface::class, $res);
+        $this->assertSame(200, $res->getStatusCode());
+        $this->assertInternalType('string', $res->getReasonPhrase());
+    }
+}
diff --git a/test/ServerRequestTest.php b/test/ServerRequestTest.php
new file mode 100644
index 0000000..7cad8fe
--- /dev/null
+++ b/test/ServerRequestTest.php
@@ -0,0 +1,32 @@
+<?php
+/**
+ * Created by PhpStorm.
+ * User: Inhere
+ * Date: 2018/3/28 0028
+ * Time: 22:05
+ */
+
+namespace Inhere\Http\Test;
+
+use Inhere\Http\ServerRequest;
+use PHPUnit\Framework\TestCase;
+use Psr\Http\Message\RequestInterface;
+
+/**
+ * Class RequestTest
+ * @package Inhere\Http\Test
+ */
+class ServerRequestTest extends TestCase
+{
+    public function testClass()
+    {
+        $req = new ServerRequest();
+
+        $this->assertInstanceOf(RequestInterface::class, $req);
+
+        $req = $req->withAttribute('key', 'value');
+
+        $this->assertInstanceOf(RequestInterface::class, $req);
+        $this->assertSame('value', $req->getAttribute('key'));
+    }
+}