diff --git a/tests/HTTP/MessageTest.php b/tests/HTTP/MessageTest.php
index 0ca19ba..78e5931 100644
--- a/tests/HTTP/MessageTest.php
+++ b/tests/HTTP/MessageTest.php
@@ -42,6 +42,45 @@ function testStringBody() {
 
     }
 
+    /**
+     * @expectedException \UnexpectedValueException
+     */
+    function testCallbackBodyAsString() {
+
+        $body = $this->createCallback();
+
+        $message = new MessageMock();
+        $message->setBody($body);
+
+        $message->getBodyAsString();
+
+    }
+
+    /**
+     * @expectedException \UnexpectedValueException
+     */
+    function testCallbackBodyAsStream() {
+
+        $body = $this->createCallback();
+
+        $message = new MessageMock();
+        $message->setBody($body);
+
+        $message->getBodyAsStream();
+
+    }
+
+    function testGetBodyWhenCallback() {
+
+        $body = $this->createCallback();
+
+        $message = new MessageMock();
+        $message->setBody($body);
+
+        $this->assertEquals($body, $message->getBody());
+
+    }
+
     /**
      * It's possible that streams contains more data than the Content-Length.
      *
@@ -219,6 +258,15 @@ function testHasHeaders() {
 
     }
 
+    private function createCallback()
+    {
+        return function() {
+            $fd = fopen('php://output', 'r+');
+            fwrite($fd, 'foo');
+            fclose($fd);
+        };
+    }
+
 }
 
 class MessageMock extends Message { }
diff --git a/tests/HTTP/SapiTest.php b/tests/HTTP/SapiTest.php
index 158ce21..935b8f6 100644
--- a/tests/HTTP/SapiTest.php
+++ b/tests/HTTP/SapiTest.php
@@ -164,4 +164,25 @@ function testSendLimitedByContentLengthStream() {
 
     }
 
+    /**
+     * @runInSeparateProcess
+     * @depends testSend
+     */
+    function testSendWorksWithCallbackAsBody() {
+        $response = new Response(200, [], function() {
+            $fd = fopen('php://output', 'r+');
+            fwrite($fd, 'foo');
+            fclose($fd);
+        });
+
+        ob_start();
+
+        Sapi::sendResponse($response);
+
+        $result = ob_get_clean();
+
+        $this->assertEquals('foo', $result);
+
+    }
+
 }