Added server tests

Response.go

@@ -20,7 +20,7 @@ type Response interface {
 // response represents the HTTP response used in the given context.
 type response struct {
 	body    []byte
-	headers []header
+	headers []Header
 	status  uint16
 }
 
@@ -49,7 +49,7 @@ func (res *response) SetHeader(key string, value string) {
 		}
 	}
 
-	res.headers = append(res.headers, header{Key: key, Value: value})
+	res.headers = append(res.headers, Header{Key: key, Value: value})
 }
 
 // SetBody replaces the response body with the new contents.