diff --git a/api/components/TestData.php b/api/components/TestData.php
new file mode 100644
index 0000000..ac4b417
--- /dev/null
+++ b/api/components/TestData.php
@@ -0,0 +1,174 @@
+<?php
+namespace api\components;
+
+use Closure;
+use Yii;
+use yii\base\ActionEvent;
+use yii\helpers\Json;
+use yii\web\Request;
+
+class TestData {
+
+    private const MAP = [
+        'signup/index' => 'beforeSignup',
+        'signup/repeat-message' => 'beforeRepeatMessage',
+        'signup/confirm' => 'beforeSignupConfirm',
+        'authentication/forgot-password' => 'beforeForgotPassword',
+        'authentication/recover-password' => 'beforeRecoverPassword',
+        'default/get' => 'beforeAccountGet',
+        'default/email-verification' => 'beforeAccountEmailVerification',
+        'default/new-email-verification' => 'beforeAccountNewEmailVerification',
+        'default/email' => 'beforeAccountChangeEmail',
+    ];
+
+    public static function getInstance(): callable {
+        return Closure::fromCallable([new static(), 'beforeAction']);
+    }
+
+    public function beforeAction(ActionEvent $event): void {
+        $id = $event->action->controller->id . '/' . $event->action->id;
+        if (!isset(self::MAP[$id])) {
+            return;
+        }
+
+        $handler = self::MAP[$id];
+        $request = Yii::$app->request;
+        $response = Yii::$app->response;
+        $result = $this->$handler($request, $response);
+        if ($result === null) {
+            return;
+        }
+
+        $response->content = Json::encode($result);
+
+        // Prevent request execution
+        $event->isValid = false;
+        $event->handled = true;
+    }
+
+    public function beforeSignup(Request $request): ?array {
+        $email = $request->post('email');
+        if ($email === 'let-me-register@ely.by') {
+            return ['success' => true];
+        }
+
+        return null;
+    }
+
+    public function beforeRepeatMessage(Request $request): ?array {
+        $email = $request->post('email');
+        if ($email === 'let-me-register@ely.by' || $email === 'let-me-repeat@ely.by') {
+            return ['success' => true];
+        }
+
+        return null;
+    }
+
+    public function beforeSignupConfirm(Request $request): ?array {
+        $email = $request->post('key');
+        if ($email === 'LETMEIN') {
+            return [
+                'success' => true,
+                'access_token' => 'dummy_token',
+                'expires_in' => time() + 60,
+            ];
+        }
+
+        return null;
+    }
+
+    public function beforeForgotPassword(Request $request): ?array {
+        $login = $request->post('login');
+        if ($login === 'let-me-recover@ely.by') {
+            return [
+                'success' => true,
+                'data' => [
+                    'canRepeatIn' => time() + 60,
+                    'repeatFrequency' => 60,
+                ],
+            ];
+        }
+
+        return null;
+    }
+
+    public function beforeRecoverPassword(Request $request): ?array {
+        $key = $request->post('key');
+        if ($key === 'LETMEIN') {
+            return [
+                'success' => true,
+                'access_token' => 'dummy_token',
+                'expires_in' => time() + 60,
+            ];
+        }
+
+        return null;
+    }
+
+    public function beforeAccountGet(Request $request): ?array {
+        $httpAuth = $request->getHeaders()->get('authorization');
+        if ($httpAuth === 'Bearer dummy_token') {
+            return [
+                'id' => 1,
+                'uuid' => 'f63cd5e1-680f-4c2d-baa2-cc7bb174b71a',
+                'username' => 'dummy',
+                'isOtpEnabled' => false,
+                'registeredAt' => time(),
+                'lang' => 'en',
+                'elyProfileLink' => 'http://ely.by/u1',
+                'email' => 'let-me-register@ely.by',
+                'isActive' => true,
+                'passwordChangedAt' => time(),
+                'hasMojangUsernameCollision' => false,
+                'shouldAcceptRules' => false,
+            ];
+        }
+
+        return null;
+    }
+
+    public function beforeAccountEmailVerification(Request $request): ?array {
+        $httpAuth = $request->getHeaders()->get('authorization');
+        if ($httpAuth === 'Bearer dummy_token') {
+            $password = $request->post('password');
+            if (empty($password)) {
+                return [
+                    'success' => false,
+                    'errors' => [
+                        'password' => 'error.password_required',
+                    ],
+                ];
+            }
+
+            return [
+                'success' => true,
+            ];
+        }
+
+        return null;
+    }
+
+    public function beforeAccountNewEmailVerification(Request $request): ?array {
+        $key = $request->post('key');
+        if ($key === 'LETMEIN') {
+            return [
+                'success' => true,
+            ];
+        }
+
+        return null;
+    }
+
+    public function beforeAccountChangeEmail(Request $request): ?array {
+        $key = $request->post('key');
+        if ($key === 'LETMEIN') {
+            return [
+                'success' => true,
+                'email' => 'brand-new-email@ely.by',
+            ];
+        }
+
+        return null;
+    }
+
+}
diff --git a/api/config/config.php b/api/config/config.php
index 8969ef5..c38ea0c 100644
--- a/api/config/config.php
+++ b/api/config/config.php
@@ -87,4 +87,5 @@ return [
         'internal' => api\modules\internal\Module::class,
         'accounts' => api\modules\accounts\Module::class,
     ],
+    'on beforeAction' => api\components\TestData::getInstance(),
 ];