diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 00000000..6ae72673
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,27 @@
+language: php
+
+sudo: false
+
+# whitelist for building branches
+branches:
+  only:
+    - master
+    - stable
+
+matrix:
+    include:
+        - php: 5.3
+        - php: 5.4
+        - php: 5.5
+        - php: 5.6
+        - php: 7
+    fast_finish: true
+
+before_install:
+    - composer self-update
+
+before_script:
+    - composer install
+
+script:
+    - vendor/bin/phpunit --bootstrap vendor/autoload.php  tests/
diff --git a/README.md b/README.md
index 5726545c..2da405c9 100644
--- a/README.md
+++ b/README.md
@@ -176,3 +176,6 @@ echo $transaction->isPaid()?'Paid':'Not paid';
 
 
 ```
+
+### Testing
+Please run ```vendor/bin/phpunit --bootstrap vendor/autoload.php  tests/``` to test the application
diff --git a/composer.json b/composer.json
index cd74305c..8fa1f8de 100644
--- a/composer.json
+++ b/composer.json
@@ -3,6 +3,9 @@
     "require": {
         "php-curl-class/php-curl-class": "^4.8"
     },
+    "require-dev": {
+        "phpunit/phpunit": "^4.8"
+    },
     "authors": [
         {
             "name": "Andy Pieters",
diff --git a/src/Api/Api.php b/src/Api/Api.php
index 8be251aa..0790b8c3 100644
--- a/src/Api/Api.php
+++ b/src/Api/Api.php
@@ -93,7 +93,7 @@ public function doRequest($endpoint, $version = null)
 
         $uri = Config::getApiUrl($endpoint, $version);
 
-        $curl = new Curl();
+        $curl = Config::getCurl();
 
         if(Config::getCAInfoLocation()){
             // set a custom CAInfo file
diff --git a/src/Config.php b/src/Config.php
index e31b433d..6b4f603e 100644
--- a/src/Config.php
+++ b/src/Config.php
@@ -19,6 +19,8 @@
 
 namespace Paynl;
 
+use Curl\Curl;
+
 /**
  * Description of Pay
  *
@@ -36,6 +38,8 @@ class Config
     // @var int The version of the Pay.nl API to use for requests.
     private static $apiVersion = 5;
 
+    private static $curl;
+
     /**
      * @var string path tho CAInfo location
      */
@@ -123,4 +127,27 @@ public static function getApiUrl($endpoint, $version = null)
         return self::$apiBase . '/v' . $version . '/' . $endpoint . '/json';
     }
 
+    /**
+     * @return object
+     */
+    public static function getCurl()
+    {
+        if (null === self::$curl) {
+            self::$curl = new Curl();
+        }
+
+        return self::$curl;
+    }
+
+    /**
+     * @param mixed $curl
+     */
+    public static function setCurl($curl)
+    {
+        if (is_string($curl)) {
+            $curl = new $curl;
+        }
+
+        self::$curl = $curl;
+    }
 }
diff --git a/tests/ConfigTest.php b/tests/ConfigTest.php
new file mode 100644
index 00000000..c617018a
--- /dev/null
+++ b/tests/ConfigTest.php
@@ -0,0 +1,41 @@
+<?php
+
+class ConfigTest extends PHPUnit_Framework_TestCase
+{
+    public function testCAInfoLocation()
+    {
+        \Paynl\Config::setCAInfoLocation('test/location');
+
+        $this->assertEquals('test/location',
+            \Paynl\Config::getCAInfoLocation());
+    }
+
+    public function testApiToken()
+    {
+        \Paynl\Config::setApiToken('my-api-token');
+
+        $this->assertEquals('my-api-token', \Paynl\Config::getApiToken());
+    }
+
+    public function testServiceId()
+    {
+        \Paynl\Config::setServiceId('my-service-id');
+
+        $this->assertEquals('my-service-id', \Paynl\Config::getServiceId());
+    }
+
+    public function testApiVersion()
+    {
+        \Paynl\Config::setServiceId('api-version');
+
+        $this->assertEquals('api-version', \Paynl\Config::getServiceId());
+    }
+
+    public function testApiUrl()
+    {
+        $this->assertEquals(
+            'https://rest-api.pay.nl/v5/transaction/json',
+            \Paynl\Config::getApiUrl('transaction', 5)
+        );
+    }
+}
diff --git a/tests/HelperTest.php b/tests/HelperTest.php
new file mode 100644
index 00000000..4d9c878e
--- /dev/null
+++ b/tests/HelperTest.php
@@ -0,0 +1,37 @@
+<?php
+
+class HelperTest extends PHPUnit_Framework_TestCase
+{
+    public function testRequireApiTokenException()
+    {
+        $this->setExpectedException('\Paynl\Error\Required\ApiToken');
+
+        \Paynl\Config::setApiToken('');
+        \Paynl\Helper::requireApiToken();
+    }
+
+    public function testRequireServiceIdException()
+    {
+        $this->setExpectedException('\Paynl\Error\Required\ServiceId');
+
+        \Paynl\Config::setServiceId('');
+        \Paynl\Helper::requireServiceId();
+    }
+
+    public function testCalculateTaxClass()
+    {
+        $calculatedTaxClass = \Paynl\Helper::calculateTaxClass(10, 0.6);
+
+        $this->assertEquals('L', $calculatedTaxClass);
+    }
+
+    public function testSplitAddress()
+    {
+        $splittedAddress = \Paynl\Helper::splitAddress('Voorstraat 2');
+
+        $this->assertEquals(array(
+            'Voorstraat',
+            '2'
+        ), $splittedAddress);
+    }
+}