diff --git a/documentation/hoeringsportal_deskpro.hack.patch b/documentation/hoeringsportal_deskpro.hack.patch
deleted file mode 100644
index a88cf19b5..000000000
--- a/documentation/hoeringsportal_deskpro.hack.patch
+++ /dev/null
@@ -1,37 +0,0 @@
-diff --git a/web/modules/custom/hoeringsportal_deskpro/hoeringsportal_deskpro.module b/web/modules/custom/hoeringsportal_deskpro/hoeringsportal_deskpro.module
-index d5026c34..5ce33a38 100644
---- a/web/modules/custom/hoeringsportal_deskpro/hoeringsportal_deskpro.module
-+++ b/web/modules/custom/hoeringsportal_deskpro/hoeringsportal_deskpro.module
-@@ -73,6 +73,7 @@ function hoeringsportal_deskpro_theme() {
-  * Implements hook_form_alter().
-  */
- function hoeringsportal_deskpro_form_alter(&$form, FormStateInterface $form_state, $form_id) {
-+  return;
-   if ($form_id === 'node_hearing_form' || $form_id === 'node_hearing_edit_form') {
-     // Department as select control.
-     if (isset($form['field_deskpro_department_id']['widget'][0]['value']['#type'])
-diff --git a/web/modules/custom/hoeringsportal_deskpro/src/Plugin/Validation/Constraint/AgentEmailContraintValidator.php b/web/modules/custom/hoeringsportal_deskpro/src/Plugin/Validation/Constraint/AgentEmailContraintValidator.php
-index a80a11fd..1c8e335b 100644
---- a/web/modules/custom/hoeringsportal_deskpro/src/Plugin/Validation/Constraint/AgentEmailContraintValidator.php
-+++ b/web/modules/custom/hoeringsportal_deskpro/src/Plugin/Validation/Constraint/AgentEmailContraintValidator.php
-@@ -41,6 +41,7 @@ public static function create(ContainerInterface $container) {
-    * {@inheritDoc}
-    */
-   public function validate($value, Constraint $constraint) {
-+    return;
-     // This is a single-item field so we only need to
-     // validate the first item.
-     $item = $value->first();
-diff --git a/web/modules/custom/hoeringsportal_deskpro/src/Service/DeskproService.php b/web/modules/custom/hoeringsportal_deskpro/src/Service/DeskproService.php
-index e020e97c..cd206dfb 100644
---- a/web/modules/custom/hoeringsportal_deskpro/src/Service/DeskproService.php
-+++ b/web/modules/custom/hoeringsportal_deskpro/src/Service/DeskproService.php
-@@ -531,6 +531,8 @@ public function getDefaultTicketLanguage() {
-    * Convenience function for getting data from the Deskpro client.
-    */
-   private function get($endpoint, array $query = []) {
-+    return new ApiResponse([], [], []);
-+
-     $cache = \Drupal::cache('data');
-     $cacheKey = __METHOD__ . '||' . json_encode(func_get_args());
-     $cacheTtl = $this->config->getCacheTtl();
diff --git a/documentation/localDevelopment.md b/documentation/localDevelopment.md
index 189d2d1ab..4bfd05007 100644
--- a/documentation/localDevelopment.md
+++ b/documentation/localDevelopment.md
@@ -157,10 +157,6 @@ for further details.
 composer install --no-dev --optimize-autoloader
 ```
 
-## Deskpro local hack patch
+## Deskpro
 
-Run
-
-```sh
-git apply < documentation/hoeringsportal_deskpro.hack.patch
-```
+See [hoeringsportal_deskpro/README.md](web/modules/custom/hoeringsportal_deskpro/README.md#test-mode).
diff --git a/web/modules/custom/hoeringsportal_deskpro/README.md b/web/modules/custom/hoeringsportal_deskpro/README.md
index 954ce3b88..7052b1616 100644
--- a/web/modules/custom/hoeringsportal_deskpro/README.md
+++ b/web/modules/custom/hoeringsportal_deskpro/README.md
@@ -8,6 +8,16 @@ Edit configuration on `/admin/site-setup/deskpro`.
 
 Check out `/hoeringsportal_deskpro/api/docs` for details.
 
+## Test mode
+
+During testing and development, you can make this module run in test mode and not call an actual Deskpro API. Enable
+test mode in `settings.local.php`:
+
+```php
+# settings.local.php
+$settings['hoeringsportal_deskpro']['test_mode'] = TRUE;
+```
+
 ## Drush commands
 
 ```sh
diff --git a/web/modules/custom/hoeringsportal_deskpro/src/Service/DeskproService.php b/web/modules/custom/hoeringsportal_deskpro/src/Service/DeskproService.php
index e020e97c9..b802f2cff 100644
--- a/web/modules/custom/hoeringsportal_deskpro/src/Service/DeskproService.php
+++ b/web/modules/custom/hoeringsportal_deskpro/src/Service/DeskproService.php
@@ -3,12 +3,15 @@
 namespace Drupal\hoeringsportal_deskpro\Service;
 
 use Deskpro\API\APIResponse;
+use Deskpro\API\APIResponseInterface;
 use Deskpro\API\DeskproClient;
 use Deskpro\API\Exception\APIException;
 use Drupal\Core\Language\LanguageManagerInterface;
+use Drupal\Core\Site\Settings;
 use Drupal\hoeringsportal_deskpro\Exception\DeskproException;
 use Drupal\hoeringsportal_deskpro\State\DeskproConfig;
 use GuzzleHttp\Client;
+use Symfony\Component\Yaml\Yaml;
 
 /**
  * Deskpro service.
@@ -283,7 +286,7 @@ public function getTicketMessages($ticketId, array $query = []) {
   public function getMessageAttachments($message, array $query = []) {
     $query['ticket'] = $message['ticket'];
     $query['id'] = $message['id'];
-    $response = $this->get('tickets/{ticket}/messages/{id}/attachments', $query);
+    $response = $this->get('/tickets/{ticket}/messages/{id}/attachments', $query);
 
     return $response;
   }
@@ -293,7 +296,7 @@ public function getMessageAttachments($message, array $query = []) {
    */
   public function getPerson($id, array $query = []) {
     $query['id'] = $id;
-    $response = $this->get('people/{id}', $query);
+    $response = $this->get('/people/{id}', $query);
 
     return $response;
   }
@@ -503,7 +506,7 @@ public function getTicketCustomFields() {
    * Get agents.
    */
   public function getAgents() {
-    return $this->get('agents');
+    return $this->get('/agents');
   }
 
   /**
@@ -530,7 +533,11 @@ public function getDefaultTicketLanguage() {
   /**
    * Convenience function for getting data from the Deskpro client.
    */
-  private function get($endpoint, array $query = []) {
+  private function get($endpoint, array $query = []): APIResponseInterface {
+    if (self::isTestMode()) {
+      return $this->createMockResponse($endpoint, $query);
+    }
+
     $cache = \Drupal::cache('data');
     $cacheKey = __METHOD__ . '||' . json_encode(func_get_args());
     $cacheTtl = $this->config->getCacheTtl();
@@ -728,6 +735,36 @@ public function getLanguages(array $query = []) {
     return $response;
   }
 
+  /**
+   * Is test mode?
+   */
+  public static function isTestMode() {
+    return (bool) (Settings::get('hoeringsportal_deskpro')['test_mode'] ?? FALSE);
+  }
+
+  /**
+   * Create mock response.
+   */
+  private function createMockResponse(string $endpoint, array $query): APIResponseInterface {
+    $data = [];
+    $meta = [];
+    $linked = [];
+
+    $filename = __DIR__ . '/mock/' . $endpoint . '.yaml';
+    if (file_exists($filename)) {
+      try {
+        $stuff = Yaml::parseFile($filename);
+        $data = $stuff['data'] ?? [];
+        $meta = $stuff['meta'] ?? [];
+        $linked = $stuff['linked'] ?? [];
+      }
+      catch (\Exception) {
+      }
+    }
+
+    return new APIResponse($data, $meta, $linked);
+  }
+
   /**
    * Filter tickets.
    */
diff --git a/web/modules/custom/hoeringsportal_deskpro/src/Service/mock/agents.yaml b/web/modules/custom/hoeringsportal_deskpro/src/Service/mock/agents.yaml
new file mode 100644
index 000000000..8353b9371
--- /dev/null
+++ b/web/modules/custom/hoeringsportal_deskpro/src/Service/mock/agents.yaml
@@ -0,0 +1,20 @@
+data:
+  - id: 007
+    primary_email: 007@example.com
+    first_name: James
+    last_name: Bond
+    title_prefix: ''
+    name: James Bond
+    display_name: James Bond
+    is_agent: true
+    avatar:
+      default_url_pattern: https://example.com/file.php/avatar/{{IMG_SIZE}}/default.jpg?size-fit=1
+      url_pattern: null
+      base_gravatar_url: null
+    online: false
+    online_for_chat: false
+    last_seen: null
+    agent_data: null
+
+meta: []
+linked: []
diff --git a/web/modules/custom/hoeringsportal_deskpro/src/Service/mock/ticket_departments.yaml b/web/modules/custom/hoeringsportal_deskpro/src/Service/mock/ticket_departments.yaml
new file mode 100644
index 000000000..9a266157f
--- /dev/null
+++ b/web/modules/custom/hoeringsportal_deskpro/src/Service/mock/ticket_departments.yaml
@@ -0,0 +1,19 @@
+data:
+  - id: 1
+    parent: null
+    children: []
+    title: Høringssvar
+    user_title: Høringssvar
+    full_title: Høringssvar
+    is_tickets_enabled: true
+    is_chat_enabled: false
+    display_order: 0
+    avatar:
+      default_url_pattern: https://example.com/file.php/o-avatar/default?s={{IMG_SIZE}}&size-fit=1
+      url_pattern: null
+      base_gravatar_url: null
+    brands:
+      - 1
+
+meta: []
+linked: []