diff --git a/config/install/payment.payment_method_configuration.payment_datatrans.yml b/config/install/payment.payment_method_configuration.payment_datatrans.yml
index 3c474c0..43c6d6e 100644
--- a/config/install/payment.payment_method_configuration.payment_datatrans.yml
+++ b/config/install/payment.payment_method_configuration.payment_datatrans.yml
@@ -14,5 +14,6 @@ pluginConfiguration:
     hmac_key: '12345'
     hmac_key_2: ''
     use_hmac_2: FALSE
+  debug: FALSE
 pluginId: payment_datatrans
 status: true
diff --git a/config/schema/payment_datatrans.schema.yml b/config/schema/payment_datatrans.schema.yml
index dbf0563..8674ed0 100644
--- a/config/schema/payment_datatrans.schema.yml
+++ b/config/schema/payment_datatrans.schema.yml
@@ -32,3 +32,6 @@ payment.plugin_configuration.payment_method_configuration.payment_datatrans:
         use_hmac_2:
           type: boolean
           label: Use HMAC 2
+    debug:
+      type: boolean
+      label: Log Datatrans responses
diff --git a/src/Controller/DatatransResponseController.php b/src/Controller/DatatransResponseController.php
index 0e6f33c..1c06a64 100644
--- a/src/Controller/DatatransResponseController.php
+++ b/src/Controller/DatatransResponseController.php
@@ -12,8 +12,9 @@
 use Symfony\Component\HttpFoundation\Request;
 
 /**
- * Class DatatransResponseController
- *   Datatrans Response Controller
+ * Class DatatransResponseController.
+ *
+ * Datatrans Response Controller
  *
  * @package Drupal\payment_datatrans\Controller
  */
@@ -22,15 +23,24 @@ class DatatransResponseController {
   /**
    * Page callback for processing successful Datatrans response.
    *
-   * @param Request $request
-   *   Request
-   * @param PaymentInterface $payment
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   Request.
+   * @param \Drupal\payment\Entity\PaymentInterface $payment
    *   The Payment entity type.
    *
-   * @return \Symfony\Component\HttpFoundation\Response
+   * @return \Symfony\Component\HttpFoundation\RedirectResponse
+   *    Returns the redirect response.
    */
   public function processSuccessResponse(Request $request, PaymentInterface $payment) {
     try {
+      if (\Drupal::config('payment.payment_method_configuration.payment_datatrans')->get('pluginConfiguration')['debug']) {
+        if (\Drupal::moduleHandler()->moduleExists('past')) {
+          past_event_save('datatrans', 'response_success', 'Success response - Payment ' . $payment->id() . ': POST data', ['POST' => $request->request->all(), 'Payment' => $payment]);
+        }
+        else {
+          \Drupal::logger('datatrans')->debug(t('Payment success response: @response', ['@response' => $request->request->all()]));
+        }
+      }
       // This needs to be checked to match the payment method settings
       // ND being valid with its keys and data.
       $post_data = $request->request->all();
@@ -88,15 +98,24 @@ public function processSuccessResponse(Request $request, PaymentInterface $payme
   /**
    * Page callback for processing error Datatrans response.
    *
-   * @param PaymentInterface $payment
-   *  The Payment entity type.
-   *
-   * @return \Symfony\Component\HttpFoundation\Response
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   Request.
+   * @param \Drupal\payment\Entity\PaymentInterface $payment
+   *   The Payment entity type.
    *
-   * @throws \Exception
+   * @return \Symfony\Component\HttpFoundation\RedirectResponse
+   *    Returns the redirect response.
    */
-  public function processErrorResponse(PaymentInterface $payment) {
-
+  public function processErrorResponse(Request $request, PaymentInterface $payment) {
+    if (\Drupal::config('payment.payment_method_configuration.payment_datatrans')->get('pluginConfiguration')['debug']) {
+      if (\Drupal::moduleHandler()->moduleExists('past')) {
+        past_event_save('datatrans', 'response_error', 'Error response - Payment ' . $payment->id() . ': POST data', ['POST' => $request->request->all(), 'Payment' => $payment]);
+      }
+      else {
+        \Drupal::logger('datatrans')->info(t('Payment error response: @response', ['@response' => $request->request->all()]));
+      }
+      drupal_set_message(t('Payment error response: @response', ['@response' => implode(', ', $request->request->all())]));
+    }
     $message = 'Datatrans communication failure. Invalid data received from Datatrans.';
     \Drupal::logger('datatrans')->error('Processing failed with exception @e.', array('@e' => $message));
     drupal_set_message(t('Payment processing failed.'), 'error');
@@ -106,14 +125,23 @@ public function processErrorResponse(PaymentInterface $payment) {
   /**
    * Page callback for processing cancellation Datatrans response.
    *
-   * @param PaymentInterface $payment
-   *  The Payment entity type.
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   Request received from datatrans server.
+   * @param \Drupal\payment\Entity\PaymentInterface $payment
+   *   The Payment entity type.
    *
    * @return \Symfony\Component\HttpFoundation\Response
-   *
-   * @throws \Exception
+   *    Returns the redirect response.
    */
-  public function processCancelResponse(PaymentInterface $payment) {
+  public function processCancelResponse(Request $request, PaymentInterface $payment) {
+    if (\Drupal::config('payment.payment_method_configuration.payment_datatrans')->get('pluginConfiguration')['debug']) {
+      if (\Drupal::moduleHandler()->moduleExists('past')) {
+        past_event_save('datatrans', 'response_cancel', 'Cancel response - Payment ' . $payment->id() . ': POST data', ['POST' => $request->request->all(), 'Payment' => $payment]);
+      }
+      else {
+        \Drupal::logger('datatrans')->info(t('Payment cancel response: @response', ['@response' => $request->request->all()]));
+      }
+    }
     drupal_set_message(t('Payment cancelled.'), 'error');
     return $this->savePayment($payment, 'payment_cancelled');
   }
@@ -128,9 +156,11 @@ public function processCancelResponse(PaymentInterface $payment) {
    *
    * @return string
    *   The generated sign.
+   *
    * @throws \Exception
+   *   Exception when generating the sign failed.
    */
-  public function generateSign2($plugin_definition, $post_data) {
+  public function generateSign2(array $plugin_definition, array $post_data) {
     if ($plugin_definition['security']['hmac_key'] || $plugin_definition['security']['hmac_key_2']) {
       if ($plugin_definition['security']['use_hmac_2']) {
         $key = $plugin_definition['security']['hmac_key_2'];
@@ -148,11 +178,12 @@ public function generateSign2($plugin_definition, $post_data) {
    * Saves success/cancelled/failed payment.
    *
    * @param \Drupal\payment\Entity\PaymentInterface $payment
-   *  Payment entity.
+   *   Payment entity.
    * @param string $status
-   *  Payment status to set
+   *   Payment status to set.
    *
-   * @return \Symfony\Component\HttpFoundation\RedirectResponse
+   * @return \Symfony\Component\HttpFoundation\Response
+   *   Saves payment and returns a response.
    */
   public function savePayment(PaymentInterface $payment, $status = 'payment_failed') {
     $payment->setPaymentStatus(\Drupal::service('plugin.manager.payment.status')
@@ -166,12 +197,12 @@ public function savePayment(PaymentInterface $payment, $status = 'payment_failed
    *
    * No validation.
    *
-   * @param PaymentInterface $payment
+   * @param \Drupal\payment\Entity\PaymentInterface $payment
    *   Payment Interface.
-   * @param $post_data
+   * @param array $post_data
    *   Datatrans Post Data.
    */
-  public function setPaymentConfiguration(PaymentInterface $payment, $post_data) {
+  public function setPaymentConfiguration(PaymentInterface $payment, array $post_data) {
     /** @var \Drupal\payment_datatrans\Plugin\Payment\Method\DatatransMethod $payment_method */
     $payment_method = $payment->getPaymentMethod();
 
diff --git a/src/Plugin/Payment/MethodConfiguration/DatatransConfiguration.php b/src/Plugin/Payment/MethodConfiguration/DatatransConfiguration.php
index 06911fd..8755cea 100644
--- a/src/Plugin/Payment/MethodConfiguration/DatatransConfiguration.php
+++ b/src/Plugin/Payment/MethodConfiguration/DatatransConfiguration.php
@@ -87,6 +87,7 @@ public function defaultConfiguration() {
         'hmac_key_2' => '',
         'use_hmac_2' => FALSE,
       ),
+      'debug' => FALSE,
     );
   }
 
@@ -332,6 +333,23 @@ public function getHmacKeyTwo() {
     return $this->configuration['security']['hmac_key_2'];
   }
 
+  /**
+   * Enables logging the response from Datatrans.
+   *
+   * @param bool $state
+   *   Whether debugging should be dis/enabled.
+   */
+  public function setDebug($state = TRUE) {
+    $this->configuration['debug'] = $state;
+  }
+
+  /**
+   * Disables logging the response from Datatrans.
+   */
+  public function getDebug() {
+    return $this->configuration['debug'];
+  }
+
   /**
    * {@inheritdoc}
    */
@@ -432,6 +450,12 @@ public function buildConfigurationForm(array $form, FormStateInterface $form_sta
       ),
     );
 
+    $form['debug'] = array(
+      '#type' => 'checkbox',
+      '#title' => 'Log response from Datatrans server',
+      '#default_value' => $this->getDebug(),
+    );
+
     return $form;
   }
 
@@ -449,7 +473,8 @@ public function formElementsValidate(array $element, FormStateInterface $form_st
       ->setMerchantControlConstant($values['security']['merchant_control_constant'])
       ->setHmacKey($values['security']['hmac_key'])
       ->setUseHmacTwo($values['security']['use_hmac_2'])
-      ->setHmacKeyTwo($values['security']['hmac_key_2']);
+      ->setHmacKeyTwo($values['security']['hmac_key_2'])
+      ->setDebug($values['debug']);
   }
 
 }
diff --git a/src/Tests/DatatransPaymentTest.php b/src/Tests/DatatransPaymentTest.php
index 07ba26e..fa8e86f 100644
--- a/src/Tests/DatatransPaymentTest.php
+++ b/src/Tests/DatatransPaymentTest.php
@@ -27,7 +27,8 @@ class DatatransPaymentTest extends WebTestBase {
     'payment_datatrans_test',
     'node',
     'field_ui',
-    'config'
+    'config',
+    'dblog',
   );
 
   /**
@@ -95,7 +96,8 @@ protected function setUp() {
       'access content',
       'access administration pages',
       'access user profiles',
-      'payment.payment.view.any'
+      'access site reports',
+      'payment.payment.view.any',
     ));
     $this->drupalLogin($this->adminUser);
   }
@@ -103,7 +105,7 @@ protected function setUp() {
   /**
    * Tests succesfull Datatrans payment.
    */
-  function testDatatransSuccessPayment() {
+  public function testDatatransSuccessPayment() {
     // Modifies the datatrans configuration for testing purposes.
     $generator = \Drupal::urlGenerator();
     $datatrans_configuration = array(
@@ -118,23 +120,33 @@ function testDatatransSuccessPayment() {
     );
     $this->drupalPostForm('admin/config/services/payment/method/configuration/payment_datatrans', $datatrans_configuration, t('Save'));
 
-    // Create datatrans payment
+    $this->drupalGet('admin/config/services/payment/method/configuration/payment_datatrans');
+    // Test the debug checkbox.
+    $this->assertNoFieldChecked('edit-plugin-form-debug');
+    $edit = [
+      'plugin_form[debug]' => TRUE,
+    ];
+    $this->drupalPostForm(NULL, $edit, t('Save'));
+    $this->drupalGet('admin/config/services/payment/method/configuration/payment_datatrans');
+    $this->assertFieldChecked('edit-plugin-form-debug');
+
+    // Create datatrans payment.
     $this->drupalPostForm('node/' . $this->node->id(), array(), t('Pay'));
 
-    // Retrieve plugin configuration of created node
+    // Retrieve plugin configuration of created node.
     $plugin_configuration = $this->node->{$this->fieldName}->plugin_configuration;
 
     // Array of Datatrans payment method configuration.
     $datatrans_payment_method_configuration = entity_load('payment_method_configuration', 'payment_datatrans')->getPluginConfiguration();
 
-    // Check for correct Merchant ID
+    // Check for correct Merchant ID.
     $this->assertText('merchantId' . $datatrans_payment_method_configuration['merchant_id']);
 
-    // Check for correct amount
+    // Check for correct amount.
     $calculated_amount = $this->calculateAmount($plugin_configuration['amount'], $plugin_configuration['quantity'], $plugin_configuration['currency_code']);
     $this->assertText('amount' . $calculated_amount);
 
-    // Check for correct success, error and cancel url
+    // Check for correct success, error and cancel url.
     $this->assertText('successUrl' . $generator->generateFromRoute('payment_datatrans.response_success', array('payment' => 1), array('absolute' => TRUE)));
     $this->assertText('errorUrl' . $generator->generateFromRoute('payment_datatrans.response_error', array('payment' => 1), array('absolute' => TRUE)));
     $this->assertText('cancelUrl' . $generator->generateFromRoute('payment_datatrans.response_cancel', array('payment' => 1), array('absolute' => TRUE)));
@@ -142,19 +154,19 @@ function testDatatransSuccessPayment() {
     // Check for correct sign with using hmac_key
     $this->assertText('sign' . '309dd30ad0cb07770d3a1ffda64585a9');
 
-    // Finish and save payment
+    // Finish and save payment.
     $this->drupalPostForm(NULL, array(), t('Submit'));
 
-    // Check out the payment overview page
+    // Check out the payment overview page.
     $this->drupalGet('admin/content/payment');
 
-    // Check for correct currency code and payment amount
+    // Check for correct currency code and payment amount.
     $this->assertText('CHF 246.00');
 
-    // Check for correct Payment Method
+    // Check for correct Payment Method.
     $this->assertText('Datatrans');
 
-    // Check payment configuration (city, street & zipcode)
+    // Check payment configuration (city, street & zipcode).
     /** @var \Drupal\payment\Entity\PaymentInterface $payment */
     $payment = entity_load('payment', 1);
     $payment_method = $payment->getPaymentMethod();
@@ -167,20 +179,24 @@ function testDatatransSuccessPayment() {
     $this->assertTrue($payment_configuration['uppCustomerStreet'], 'street');
     $this->assertTrue($payment_configuration['uppCustomerZipCode'], 'CHE');
 
-    // Check for detailed payment information
+    // Check for detailed payment information.
     $this->drupalGet('payment/1');
     $this->assertNoText('Failed');
     $this->assertText('Payment description');
     $this->assertText('CHF 123.00');
     $this->assertText('CHF 246.00');
     $this->assertText('Completed');
+
+    $this->drupalGet('/admin/reports/dblog');
+    $this->assertText('Payment success response: POST');
   }
 
   /**
    * Tests failing Datatrans payment.
+   *
    * The test fails by providing an incorrect hmac key.
    */
-  function testDatatransFailedPayment() {
+  public function testDatatransFailedPayment() {
     // Modifies the datatrans configuration for testing purposes.
     $generator = \Drupal::urlGenerator();
     $datatrans_configuration = array(
@@ -193,35 +209,40 @@ function testDatatransFailedPayment() {
       'plugin_form[security][hmac_key]' => '1234',
       // For failed test we give a wrong hmac_key
       'plugin_form[security][hmac_key_2]' => '',
+      'plugin_form[debug]' => TRUE,
     );
     $this->drupalPostForm('admin/config/services/payment/method/configuration/payment_datatrans', $datatrans_configuration, t('Save'));
 
-    // Create datatrans payment
+    // Create datatrans payment.
     \Drupal::state()->set('datatrans.return_url_key', 'error');
     $this->drupalPostForm('node/' . $this->node->id(), array(), t('Pay'));
 
     // Check for incorrect sign.
     $this->assertNoText('sign309dd30ad0cb07770d3a1ffda64585a9');
 
-    // Finish and save payment
+    // Finish and save payment.
     $this->drupalPostForm(NULL, array(), t('Submit'));
 
-    // Check out the payment overview page
+    // Check out the payment overview page.
     $this->drupalGet('admin/content/payment');
     $this->assertText('Failed');
     $this->assertNoText('Success');
 
-    // Check for detailed payment information
+    // Check for detailed payment information.
     $this->drupalGet('payment/1');
     $this->assertText('Failed');
     $this->assertNoText('Success');
+
+    $this->drupalGet('/admin/reports/dblog');
+    $this->assertText('Payment error response: POST');
   }
 
   /**
    * Tests failing Datatrans payment.
+   *
    * The test fails by providing an incorrect hmac key.
    */
-  function testDatatransTestSignPayment() {
+  public function testDatatransTestSignPayment() {
     // Modifies the datatrans configuration for testing purposes.
     $generator = \Drupal::urlGenerator();
     $datatrans_configuration = array(
@@ -234,10 +255,11 @@ function testDatatransTestSignPayment() {
       'plugin_form[security][hmac_key]' => '1234',
       // For failed test we give a wrong hmac_key
       'plugin_form[security][hmac_key_2]' => '',
+      'plugin_form[debug]' => TRUE,
     );
     $this->drupalPostForm('admin/config/services/payment/method/configuration/payment_datatrans', $datatrans_configuration, t('Save'));
 
-    // Create datatrans payment
+    // Create datatrans payment.
     \Drupal::state()->set('datatrans.return_url_key', 'error');
     \Drupal::state()->set('datatrans.identifier', rand(10, 100));
 
@@ -248,24 +270,27 @@ function testDatatransTestSignPayment() {
       \Drupal::state()->get('datatrans.identifier'), '24600', 'CHF');
     $this->assertText($generated_sign);
 
-    // Finish and save payment
+    // Finish and save payment.
     $this->drupalPostForm(NULL, array(), t('Submit'));
 
-    // Check out the payment overview page
+    // Check out the payment overview page.
     $this->drupalGet('admin/content/payment');
     $this->assertText('Failed');
     $this->assertNoText('Success');
 
-    // Check for detailed payment information
+    // Check for detailed payment information.
     $this->drupalGet('payment/1');
     $this->assertText('Failed');
     $this->assertNoText('Success');
+
+    $this->drupalGet('/admin/reports/dblog');
+    $this->assertText('Payment error response: POST');
   }
 
   /**
    * Tests cancelled Datatrans payment.
    */
-  function testDatatransCancelPayment() {
+  public function testDatatransCancelPayment() {
     // Modifies the datatrans configuration for testing purposes.
     $generator = \Drupal::urlGenerator();
     $datatrans_configuration = array(
@@ -278,6 +303,7 @@ function testDatatransCancelPayment() {
       'plugin_form[security][hmac_key]' => '1234',
       // For failed test we give a wrong hmac_key
       'plugin_form[security][hmac_key_2]' => '',
+      'plugin_form[debug]' => TRUE,
     );
     $this->drupalPostForm('admin/config/services/payment/method/configuration/payment_datatrans', $datatrans_configuration, t('Save'));
 
@@ -291,67 +317,73 @@ function testDatatransCancelPayment() {
     // Check for incorrect sign.
     $this->assertNoText('sign309dd30ad0cb07770d3a1ffda64585a9');
 
-    // Check out the payment overview page
+    // Check out the payment overview page.
     $this->drupalGet('admin/content/payment');
     $this->assertText('Cancelled');
     $this->assertNoText('Failed');
     $this->assertNoText('Success');
 
-    // Check for detailed payment information
+    // Check for detailed payment information.
     $this->drupalGet('payment/1');
     $this->assertText('Cancelled');
     $this->assertNoText('Failed');
     $this->assertNoText('Success');
+
+    $this->drupalGet('/admin/reports/dblog');
+    $this->assertText('Payment cancel response: POST');
   }
 
   /**
-   * Calculates the total amount
+   * Calculates the total amount.
+   *
+   * @param int $amount
+   *   Base amount.
+   * @param int $quantity
+   *   Quantity.
+   * @param string $currency_code
+   *   Currency code.
    *
-   * @param $amount
-   *  Base amount
-   * @param $quantity
-   *  Quantity
-   * @param $currency_code
-   *  Currency code
    * @return int
-   *  Returns the total amount
+   *   Returns the total amount.
    */
-  function calculateAmount($amount, $quantity, $currency_code) {
+  public function calculateAmount($amount, $quantity, $currency_code) {
     $base_amount = $amount * $quantity;
     $currency = Currency::load($currency_code);
     return intval($base_amount * $currency->getSubunits());
   }
 
   /**
-   * Generates the sign
+   * Generates the sign.
+   *
+   * @param string $hmac_key
+   *   Hmac key.
+   * @param string $merchant_id
+   *   Merchant ID.
+   * @param string $identifier
+   *   The identifier.
+   * @param int $amount
+   *   The order amount.
+   * @param string $currency
+   *   Currency Code.
    *
-   * @param $hmac_key
-   *  hmac key
-   * @param $merchant_id
-   *  Merchant ID
-   * @param $identifier
-   * @param $amount
-   *  The order amount
-   * @param $currency
-   *  Currency Code
    * @return string
-   *  Returns the sign
+   *   Returns the sign.
    */
-  function generateSign($hmac_key, $merchant_id, $identifier, $amount, $currency) {
+  public function generateSign($hmac_key, $merchant_id, $identifier, $amount, $currency) {
     $hmac_data = $merchant_id . $amount . $currency . $identifier;
     return hash_hmac('md5', $hmac_data, pack('H*', $hmac_key));
   }
 
   /**
-   * Adds the payment field to the node
+   * Adds the payment field to the node.
    *
    * @param NodeTypeInterface $type
-   *   Node type interface type
-   *
+   *   Node type interface type.
    * @param string $label
-   *   Field label
+   *   Field label.
    *
    * @return \Drupal\Core\Entity\EntityInterface|static
+   *   Returns the payment form field.
    */
   function addPaymentFormField(NodeTypeInterface $type, $label = 'Payment Label') {
     $field_storage = FieldStorageConfig::create(array(