diff --git a/config.php b/config.php
index fdf02a4..54cfa88 100644
--- a/config.php
+++ b/config.php
@@ -3,6 +3,7 @@
 // `dev-config-profile.php` by default.
 // on production server the included profile is `prod-config-profile.php`.
 // Please do not touch.
+
 require /*PROFILE_FILE*/ "profiles/dev-config-profile.php";
 
 const SUPPORTS_FAST_REFRESH = _SUPPORTS_FAST_REFRESH;
@@ -21,3 +22,9 @@ global $_data_source_name;
 $data_source_name = $_data_source_name;
 const DATABASE_USER = _DATABASE_USER;
 const DATABASE_PASSWORD = _DATABASE_PASSWORD;
+
+
+function init_database(PDO $pdo): void {
+    _init_database($pdo);
+}
+
diff --git a/profiles/dev-config-profile.php b/profiles/dev-config-profile.php
index bd87f1d..bb510e7 100644
--- a/profiles/dev-config-profile.php
+++ b/profiles/dev-config-profile.php
@@ -1,5 +1,9 @@
 <?php
 
+use IQBall\Core\Connection;
+use IQBall\Core\Gateway\AccountGateway;
+use IQBall\Core\Model\AuthModel;
+
 $hostname = getHostName();
 $front_url = "http://$hostname:5173";
 
@@ -14,3 +18,15 @@ function _asset(string $assetURI): string {
     global $front_url;
     return $front_url . "/" . $assetURI;
 }
+
+function _init_database(PDO $pdo): void {
+    $accounts = new AccountGateway(new Connection($pdo));
+
+    $defaultAccounts = ["maxime", "mael", "yanis", "vivien"];
+
+    foreach ($defaultAccounts as $name) {
+        $email = "$name@mail.com";
+        $id = $accounts->insertAccount($name, $email, AuthModel::generateToken(), password_hash("123456", PASSWORD_DEFAULT), "https://cdn.pixabay.com/photo/2015/10/05/22/37/blank-profile-picture-973460_960_720.png");
+        $accounts->setIsAdmin($id, true);
+    }
+}
\ No newline at end of file
diff --git a/profiles/prod-config-profile.php b/profiles/prod-config-profile.php
index e9bb12c..185541a 100644
--- a/profiles/prod-config-profile.php
+++ b/profiles/prod-config-profile.php
@@ -20,3 +20,6 @@ function _asset(string $assetURI): string {
     // fallback to the uri itself.
     return $basePath . "/" . (ASSETS[$assetURI] ?? $assetURI);
 }
+
+
+function _init_database(PDO $pdo): void {}
diff --git a/sql/database.php b/sql/database.php
index af94ef2..54ee7de 100644
--- a/sql/database.php
+++ b/sql/database.php
@@ -1,9 +1,5 @@
 <?php
 
-use IQBall\Core\Connection;
-use IQBall\Core\Gateway\AccountGateway;
-use IQBall\Core\Model\AuthModel;
-
 /**
  * @return PDO The PDO instance of the configuration's database connexion.
  */
@@ -31,15 +27,3 @@ function get_database(): PDO {
     return $pdo;
 }
 
-
-function init_database(PDO $pdo): void {
-    $accounts = new AccountGateway(new Connection($pdo));
-
-    $defaultAccounts = ["maxime", "mael", "yanis", "vivien"];
-
-    foreach ($defaultAccounts as $name) {
-        $email = "$name@mail.com";
-        $id = $accounts->insertAccount($name, $email, AuthModel::generateToken(), password_hash("123456", PASSWORD_DEFAULT), "https://cdn.pixabay.com/photo/2015/10/05/22/37/blank-profile-picture-973460_960_720.png");
-        $accounts->setIsAdmin($id, true);
-    }
-}
diff --git a/src/Api/APIControl.php b/src/Api/APIControl.php
index 260575a..751fbfb 100644
--- a/src/Api/APIControl.php
+++ b/src/Api/APIControl.php
@@ -4,6 +4,7 @@ namespace IQBall\Api;
 
 use IQBall\Core\Control;
 use IQBall\Core\ControlSchemaErrorResponseFactory;
+use IQBall\Core\Http\HttpCodes;
 use IQBall\Core\Http\HttpRequest;
 use IQBall\Core\Http\HttpResponse;
 use IQBall\Core\Http\JsonHttpResponse;
@@ -13,7 +14,7 @@ class APIControl {
     private static function errorFactory(): ControlSchemaErrorResponseFactory {
         return new class () implements ControlSchemaErrorResponseFactory {
             public function apply(array $failures): HttpResponse {
-                return new JsonHttpResponse($failures);
+                return new JsonHttpResponse($failures, HttpCodes::BAD_REQUEST);
             }
         };
     }
diff --git a/src/Api/Controller/APIAccountsController.php b/src/Api/Controller/APIAccountsController.php
index 13d9db4..32fd956 100644
--- a/src/Api/Controller/APIAccountsController.php
+++ b/src/Api/Controller/APIAccountsController.php
@@ -35,7 +35,7 @@ class APIAccountsController {
     public function listUsers(array $request): HttpResponse {
         return APIControl::runCheckedFrom($request, [
             'start' => [DefaultValidators::isUnsignedInteger()],
-            'n' => [DefaultValidators::isUnsignedInteger()],
+            'n' => [DefaultValidators::isIntInRange(0, 250)],
             'search' => [DefaultValidators::lenBetween(0, 256)],
         ], function (HttpRequest $req) {
             $accounts = $this->accounts->searchAccounts(intval($req['start']), intval($req['n']), $req["search"]);
diff --git a/src/Core/Gateway/AccountGateway.php b/src/Core/Gateway/AccountGateway.php
index d6b5686..9d36f14 100644
--- a/src/Core/Gateway/AccountGateway.php
+++ b/src/Core/Gateway/AccountGateway.php
@@ -145,7 +145,7 @@ class AccountGateway {
      * @param int $start starting index of the list content
      * @return Account[]|null
      */
-    public function searchAccounts(int $start, int $n, ?string $searchString): ?array {
+    public function searchAccounts(int $start, int $n, ?string $searchString): array {
         $res = $this->con->fetch(
             "SELECT * FROM Account WHERE username LIKE '%' || :search || '%' OR email LIKE '%' || :search || '%' ORDER BY username, email LIMIT :offset, :n",
             [
diff --git a/src/Core/Model/TacticModel.php b/src/Core/Model/TacticModel.php
index 590a106..920075b 100644
--- a/src/Core/Model/TacticModel.php
+++ b/src/Core/Model/TacticModel.php
@@ -68,9 +68,9 @@ class TacticModel {
      * NOTE: if given user id does not match any user, this function returns an empty array
      *
      * @param integer $user_id
-     * @return TacticInfo[] | null
+     * @return TacticInfo[]
      */
-    public function listAllOf(int $user_id): ?array {
+    public function listAllOf(int $user_id): array {
         return$this->tactics->listAllOf($user_id);
     }
 
diff --git a/src/Core/Validation/DefaultValidators.php b/src/Core/Validation/DefaultValidators.php
index 6e64e30..c898170 100644
--- a/src/Core/Validation/DefaultValidators.php
+++ b/src/Core/Validation/DefaultValidators.php
@@ -72,7 +72,7 @@ class DefaultValidators {
 
 
     public static function isInteger(): Validator {
-        return self::regex("/^-[0-9]+$/", "field is not an integer");
+        return self::regex("/^[-+]?[0-9]+$/", "field is not an integer");
     }
 
     public static function isUnsignedInteger(): Validator {
@@ -135,10 +135,8 @@ class DefaultValidators {
 
             public function validate(string $name, $val): array {
                 $failures = [];
-                $idx = 0;
-                foreach ($val as $item) {
+                foreach ($val as $idx => $item) {
                     $failures = array_merge($failures, $this->validator->validate($name . "[$idx]", $item));
-                    $idx += 1;
                 }
 
                 return $failures;