diff --git a/lib/API/API.php b/lib/API/API.php
index ef7f1d1cdf..174c828553 100644
--- a/lib/API/API.php
+++ b/lib/API/API.php
@@ -1,5 +1,7 @@
 <?php
 namespace MailPoet\API;
+
+use MailPoet\Util\Helpers;
 use MailPoet\Util\Security;
 
 if(!defined('ABSPATH')) exit;
@@ -40,7 +42,7 @@ class API {
   function setupAjax() {
     do_action('mailpoet_api_setup', array($this));
 
-    $this->getRequestData();
+    $this->getRequestData($_POST);
 
     if($this->checkToken() === false) {
       $error_response = new ErrorResponse(
@@ -53,18 +55,19 @@ class API {
       $error_response->send();
     }
 
-    $this->processRoute();
+    $response = $this->processRoute();
+    $response->send();
   }
 
-  function getRequestData() {
-    $this->_endpoint = isset($_POST['endpoint'])
-      ? trim($_POST['endpoint'])
+  function getRequestData($data) {
+    $this->_endpoint = isset($data['endpoint'])
+      ? Helpers::underscoreToCamelCase(trim($data['endpoint']))
       : null;
-    $this->_method = isset($_POST['method'])
-      ? trim($_POST['method'])
+    $this->_method = isset($data['method'])
+      ? Helpers::underscoreToCamelCase(trim($data['method']))
       : null;
-    $this->_token = isset($_POST['token'])
-      ? trim($_POST['token'])
+    $this->_token = isset($data['token'])
+      ? trim($data['token'])
       : null;
 
     if(!$this->_endpoint || !$this->_method) {
@@ -85,8 +88,8 @@ class API {
         }
       }
 
-      $this->_data = isset($_POST['data'])
-        ? stripslashes_deep($_POST['data'])
+      $this->_data = isset($data['data'])
+        ? stripslashes_deep($data['data'])
         : array();
 
       // remove reserved keywords from data
@@ -108,6 +111,10 @@ class API {
 
   function processRoute() {
     try {
+      if(empty($this->_endpoint_class)) {
+        throw new \Exception('Invalid endpoint');
+      }
+
       $endpoint = new $this->_endpoint_class();
 
       // check the accessibility of the requested endpoint's action
@@ -129,17 +136,17 @@ class API {
             array(),
             Response::STATUS_FORBIDDEN
           );
-          $error_response->send();
+          return $error_response;
         }
       }
 
       $response = $endpoint->{$this->_method}($this->_data);
-      $response->send();
+      return $response;
     } catch(\Exception $e) {
       $error_response = new ErrorResponse(
         array($e->getCode() => $e->getMessage())
       );
-      $error_response->send();
+      return $error_response;
     }
   }
 
@@ -163,4 +170,8 @@ class API {
   function addEndpointNamespace($namespace) {
     $this->_endpoint_namespaces[] = $namespace;
   }
+
+  function getEndpointNamespaces() {
+    return $this->_endpoint_namespaces;
+  }
 }
diff --git a/tests/unit/API/APITest.php b/tests/unit/API/APITest.php
index 426725c2a0..694f639464 100644
--- a/tests/unit/API/APITest.php
+++ b/tests/unit/API/APITest.php
@@ -1,8 +1,11 @@
 <?php
+use Codeception\Util\Stub;
 use MailPoet\API\API;
+use MailPoet\API\SuccessResponse;
 
 // required to be able to use wp_delete_user()
 require_once(ABSPATH.'wp-admin/includes/user.php');
+require_once('APITestNamespacedEndpointStub.php');
 
 class APITest extends MailPoetTest {
   function _before() {
@@ -32,6 +35,52 @@ class APITest extends MailPoetTest {
     expect($this->api->checkPermissions())->true();
   }
 
+  function testItCallsAPISetupAction() {
+    $called = false;
+    add_action(
+      'mailpoet_api_setup',
+      function ($api) use (&$called) {
+        $called = true;
+        expect($api instanceof API)->true();
+      }
+    );
+    $api = Stub::makeEmptyExcept(
+      $this->api,
+      'setupAjax',
+      array(
+        'processRoute' => Stub::makeEmpty(new SuccessResponse)
+      )
+    );
+    $api->setupAjax();
+    expect($called)->true();
+  }
+
+  function testItCanAddEndpointNamespaces() {
+    expect($this->api->getEndpointNamespaces())->count(1);
+
+    $namespace = "MailPoet\\Dummy\\Name\\Space";
+    $this->api->addEndpointNamespace($namespace);
+    $namespaces = $this->api->getEndpointNamespaces();
+
+    expect($namespaces)->count(2);
+    expect($namespaces[1])->equals($namespace);
+  }
+
+  function testItCanCallAddedEndpoints() {
+    $namespace = "MailPoet\\Some\\Name\\Space\\Endpoints";
+    $this->api->addEndpointNamespace($namespace);
+
+    $data = array(
+      'endpoint' => 'namespaced_endpoint_stub',
+      'method' => 'test',
+      'data' => array('test' => 'data')
+    );
+    $this->api->getRequestData($data);
+    $response = $this->api->processRoute();
+
+    expect($response->getData()['data'])->equals($data['data']);
+  }
+
   function _after() {
     wp_delete_user($this->wp_user_id);
   }
diff --git a/tests/unit/API/APITestNamespacedEndpointStub.php b/tests/unit/API/APITestNamespacedEndpointStub.php
new file mode 100644
index 0000000000..02b196f451
--- /dev/null
+++ b/tests/unit/API/APITestNamespacedEndpointStub.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace MailPoet\Some\Name\Space\Endpoints;
+
+use MailPoet\API\Endpoint as APIEndpoint;
+use MailPoet\API\Access as APIAccess;
+
+if(!defined('ABSPATH')) exit;
+
+class NamespacedEndpointStub extends APIEndpoint {
+  public $permissions = array(
+    'test' => APIAccess::ALL
+  );
+
+  function test($data) {
+    return $this->successResponse($data);
+  }
+}