diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000000000000000000000000000000000000..9ab59b180fb670006ac910a2bc4524a1376dcea0
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,15 @@
+
+# Ignore developer files when exporting
+.gitattributes         export-ignore
+.gitignore             export-ignore
+.gitlab-ci.yml         export-ignore
+.phive                 export-ignore
+captainhook.json       export-ignore
+phpcs.xml.dist         export-ignore
+phpstan-baseline.neon  export-ignore
+phpstan.dist.neon      export-ignore
+phpunit.dist.xml       export-ignore
+tests                  export-ignore
+
+# Explicitly set file type and line endings for PHP files, improves git diff output
+*.php     text eol=lf diff=php
\ No newline at end of file
diff --git a/.gitignore b/.gitignore
index f4da20891502a3992abf2981d8f6c46e33868ab6..e25391c1f85364060ac958b37e8e35c6c51beafe 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,11 @@
 tools/
 phpstan.neon
 .phpunit.result.cache
-phpunit.xml
\ No newline at end of file
+phpunit.xml
+tools/
+
+phpstan.neon
+
+.phpunit.result.cache
+
+phpunit.xml
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b8d20acb6c365ad8036a7b36d47dabd876d08efa..b5a64b401e554341447c74d7cf93a89ac95a3fdb 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,3 +1,17 @@
 include:
-  - project: 'quiqqer/stabilization/semantic-release'
-    file: '/ci-templates/.gitlab-ci.yml'
+  - component: dev.quiqqer.com/quiqqer/stabilization/ci-cd-components/quiqqer-package-bundle/quiqqer-package-bundle@main
+
+# Remove the entire phpunit-php8.1 block, to allow PHPUnit to run on PHP 8.1 in your pipeline
+phpunit-php8.1:
+  rules:
+    - when: never
+
+# Remove the entire phpunit-php8.2 block, to allow PHPUnit to run on PHP 8.2 in your pipeline
+phpunit-php8.2:
+  rules:
+    - when: never
+
+# Remove the entire phpunit-php8.3 block, to allow PHPUnit to run on PHP 8.3 in your pipeline
+phpunit-php8.3:
+  rules:
+    - when: never
\ No newline at end of file
diff --git a/.phive/phars.xml b/.phive/phars.xml
index a1315a09b4adad780a9c5e52f74835c708c5c7d5..5bfa092bfad10dad9d23240281a5a2041acb815b 100644
--- a/.phive/phars.xml
+++ b/.phive/phars.xml
@@ -1,4 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <phive xmlns="https://phar.io/phive">
-  <phar name="phpstan" version="^1.10.67" installed="1.10.67" location="./tools/phpstan" copy="false"/>
+  <phar name="phpstan" version="1.11.8" installed="1.11.8" location="./tools/phpstan" copy="false"/>
+  <phar name="phpunit" version="^10.5.20" installed="10.5.20" location="./tools/phpunit" copy="false"/>
+  <phar name="phpcs" version="^3.10.1" installed="3.10.1" location="./tools/phpcs" copy="false"/>
+  <phar name="phpcbf" version="^3.10.1" installed="3.10.1" location="./tools/phpcbf" copy="false"/>
+  <phar name="captainhook" version="^5.23.3" installed="5.23.3" location="./tools/captainhook" copy="false"/>
 </phive>
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000000000000000000000000000000000000..4a69a59b440e5beec561eca1e341509bd5a18688
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,3 @@
+# Contributing
+
+This package follows the [QUIQQER contribution guidelines](https://dev.quiqqer.com/quiqqer/stabilization/documentation/-/wikis/home).
\ No newline at end of file
diff --git a/ajax/convertWithSign.php b/ajax/convertWithSign.php
index f7bb2e643abf445b13120af0f526195d4ee4f5fc..3ba06664741f0ff09bb82f8d264faa5c5f0b3d14 100644
--- a/ajax/convertWithSign.php
+++ b/ajax/convertWithSign.php
@@ -18,6 +18,10 @@ function ($data) {
         $data = json_decode($data, true);
         $result = [];
 
+        if (!class_exists('QUI\ERP\Money\Price')) {
+            return $result;
+        }
+
         foreach ($data as $entry) {
             $amount = $entry['amount'];
             $currencyFrom = $entry['from'];
diff --git a/captainhook.json b/captainhook.json
new file mode 100644
index 0000000000000000000000000000000000000000..3702e1a358868bedd5ff4c7eae40bb1abb589267
--- /dev/null
+++ b/captainhook.json
@@ -0,0 +1,13 @@
+{
+    "pre-commit": {
+        "enabled": true,
+        "actions": [
+            {
+                "action": "\\CaptainHook\\App\\Hook\\PHP\\Action\\Linting"
+            },
+            {
+                "action": "composer test"
+            }
+        ]
+    }
+}
\ No newline at end of file
diff --git a/composer.json b/composer.json
index 16ff89243d5cf87fa20c102a273862d8a9409265..d5c5ed21d26c0ac44bfdb0c16149f01955b12456 100644
--- a/composer.json
+++ b/composer.json
@@ -1,28 +1,70 @@
 {
-  "name": "quiqqer/currency",
-  "type": "quiqqer-module",
-  "description": "Integrates different currencies in QUIQQER",
-  "license": "GPL-3.0-or-later",
-  "authors": [
-    {
-      "name": "Henning Leutz",
-      "email": "leutz@pcsg.de",
-      "homepage": "https://www.pcsg.de",
-      "role": "Developer"
+    "name": "quiqqer/currency",
+    "type": "quiqqer-module",
+    "description": "Integrates different currencies in QUIQQER",
+    "license": "GPL-3.0-or-later",
+    "authors": [
+        {
+            "name": "Henning Leutz",
+            "email": "leutz@pcsg.de",
+            "homepage": "https://www.pcsg.de",
+            "role": "Developer"
+        }
+    ],
+    "support": {
+        "email": "support@pcsg.de"
+    },
+    "require": {
+        "php": "^8.1",
+        "ext-intl": "*",
+        "quiqqer/core": "^2",
+        "quiqqer/qui": "^1"
+    },
+    "autoload": {
+        "psr-4": {
+            "QUI\\ERP\\Currency\\": "src/QUI/ERP/Currency"
+        }
+    },
+    "scripts": {
+        "test": [
+            "@dev:lint",
+            "@dev:phpunit"
+        ],
+        "dev:phpunit": "./tools/phpunit",
+        "dev:lint": [
+            "@dev:lint:phpstan",
+            "@dev:lint:style"
+        ],
+        "dev:lint:phpstan": "./tools/phpstan",
+        "dev:lint:style": "./tools/phpcs",
+        "dev:lint:style:fix": "./tools/phpcbf",
+        "dev:init": [
+            "@dev:init:check-requirements",
+            "@dev:init:tools",
+            "@dev:init:git-hooks"
+        ],
+        "dev:init:check-requirements": [
+            "which composer > /dev/null || (echo 'Error: composer has to be globally installed'; exit 1)",
+            "which phive > /dev/null || (echo 'Error: PHIVE has to be globally installed'; exit 1)"
+        ],
+        "dev:init:tools": "phive install --temporary",
+        "dev:init:git-hooks": "./tools/captainhook install --only-enabled --force"
+    },
+    "scripts-aliases": {
+        "test": [
+            "dev:test"
+        ]
+    },
+    "scripts-descriptions": {
+        "test": "Runs linting, static analysis, and unit tests.",
+        "dev:phpunit": "Run PHPUnit test suites",
+        "dev:lint": "Run PHPStan and code style check",
+        "dev:lint:phpstan": "Run PHPStan",
+        "dev:lint:style": "Run code style check (PHP_CodeSniffer)",
+        "dev:lint:style:fix": "Try to fix code style errors automatically",
+        "dev:init": "Initialize the developer tooling (tools and git hooks)",
+        "dev:init:check-requirements": "Check if the necessary requirements are met",
+        "dev:init:tools": "Install all developer tools (requires PHIVE)",
+        "dev:init:git-hooks": "Install all git hooks (may require tools to be installed)"
     }
-  ],
-  "support": {
-    "email": "support@pcsg.de"
-  },
-  "require": {
-    "php": "^8.1",
-    "ext-intl": "*",
-    "quiqqer/core": "^2",
-    "quiqqer/qui": "^1"
-  },
-  "autoload": {
-    "psr-4": {
-      "QUI\\ERP\\Currency\\": "src/QUI/ERP/Currency"
-    }
-  }
-}
+}
\ No newline at end of file
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
new file mode 100644
index 0000000000000000000000000000000000000000..d48084fbdc86a2dbfb78dd89ab2e0b0ff2322ba7
--- /dev/null
+++ b/phpcs.xml.dist
@@ -0,0 +1,23 @@
+<?xml version="1.0"?>
+<ruleset>
+    <!-- Use PSR-12 ruleset -->
+    <rule ref="PSR12"/>
+
+    <!-- Only scan *.php files -->
+    <arg name="extensions" value="php"/>
+
+    <!-- Ignore warnings -->
+    <arg name="warning-severity" value="0"/>
+
+    <!-- Process 64 (or number of CPU cores) files in parallel -->
+    <arg name="parallel" value="64"/>
+
+    <!-- Output relative file paths, by setting the current folder as the basepath -->
+    <arg name="basepath" value="."/>
+
+    <!-- Show colored output -->
+    <arg name="colors"/>
+
+    <!-- Scan everything in the current folder -->
+    <file>.</file>
+</ruleset>
diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..1339890a6e72c75d6ae49a176d1046f0c370282f 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -0,0 +1,2 @@
+parameters:
+	ignoreErrors:
\ No newline at end of file
diff --git a/phpstan.dist.neon b/phpstan.dist.neon
index a545a041a3c5b0c758d99bf8c1c49b2a83252eaa..18db987295f4cd08f7b698474102b19b6ecf75da 100644
--- a/phpstan.dist.neon
+++ b/phpstan.dist.neon
@@ -2,7 +2,7 @@ includes:
     - phpstan-baseline.neon
 
 parameters:
-    level: 1
+    level: 5
     paths:
         - src
         - ajax
diff --git a/phpunit.dist.xml b/phpunit.dist.xml
new file mode 100644
index 0000000000000000000000000000000000000000..f6c7becf0c12757beb871a9333e2d81e02aa7cae
--- /dev/null
+++ b/phpunit.dist.xml
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit bootstrap="tests/phpunit-bootstrap.php">
+    <testsuites>
+        <testsuite name="Tests">
+            <directory>tests/</directory>
+        </testsuite>
+    </testsuites>
+</phpunit>
diff --git a/src/QUI/ERP/Currency/AbstractCurrency.php b/src/QUI/ERP/Currency/AbstractCurrency.php
index 09bed38c0dbdd1da67bbca2a907dc4b8e34cf4d2..429715aea4c1af15bfd0b003f8355c0cf6bb141a 100644
--- a/src/QUI/ERP/Currency/AbstractCurrency.php
+++ b/src/QUI/ERP/Currency/AbstractCurrency.php
@@ -182,7 +182,7 @@ public function toArray(): array
      * @param null|QUI\Locale $Locale -optional
      * @return float
      */
-    public function amount($amount, QUI\Locale $Locale = null): float
+    public function amount($amount, null |QUI\Locale $Locale = null): float
     {
         if (is_float($amount) || is_int($amount)) {
             return $amount;
@@ -215,7 +215,7 @@ public function amount($amount, QUI\Locale $Locale = null): float
      * @param null|QUI\Locale $Locale - optional, locale object
      * @return string
      */
-    public function format($amount, QUI\Locale $Locale = null): string
+    public function format($amount, null|QUI\Locale $Locale = null): string
     {
         if (!$Locale) {
             $Locale = $this->Locale;
diff --git a/src/QUI/ERP/Currency/CurrencyInterface.php b/src/QUI/ERP/Currency/CurrencyInterface.php
index 19f3c8e03f1e38a45c33df9fc289e7d7a88145ce..f03a0d196e26513055cd7292ca641b79496937b7 100644
--- a/src/QUI/ERP/Currency/CurrencyInterface.php
+++ b/src/QUI/ERP/Currency/CurrencyInterface.php
@@ -17,7 +17,7 @@ interface CurrencyInterface
      * @param QUI\Locale|null $Locale
      * @return string
      */
-    public static function getCurrencyTypeTitle(?QUI\Locale $Locale = null): string;
+    public static function getCurrencyTypeTitle(null|QUI\Locale $Locale = null): string;
 
     /**
      * Get internal identifier of the currency type.
@@ -39,7 +39,7 @@ public static function getExtraSettingsFormHtml(): ?string;
      * @param array $data
      * @param QUI\Locale|null $Locale - Locale for the currency
      */
-    public function __construct(array $data, ?QUI\Locale $Locale = null);
+    public function __construct(array $data, null|QUI\Locale $Locale = null);
 
     /**
      * Set the locale for the currency
@@ -89,7 +89,7 @@ public function toArray(): array;
      * @param null|QUI\Locale $Locale -optional
      * @return float
      */
-    public function amount($amount, QUI\Locale $Locale = null): float;
+    public function amount($amount, null|QUI\Locale $Locale = null): float;
 
     /**
      * Format an amount
@@ -98,7 +98,7 @@ public function amount($amount, QUI\Locale $Locale = null): float;
      * @param null|QUI\Locale $Locale - optional, locale object
      * @return string
      */
-    public function format($amount, QUI\Locale $Locale = null): string;
+    public function format($amount, null|QUI\Locale $Locale = null): string;
 
     /**
      * updates the currency itself?
diff --git a/src/QUI/ERP/Currency/Handler.php b/src/QUI/ERP/Currency/Handler.php
index 9b031cb3c32f914d2c0a1c79a219d43b4dfb7e1d..719c614c5af7a30aa6ea50d3c78198d7fc9641d4 100644
--- a/src/QUI/ERP/Currency/Handler.php
+++ b/src/QUI/ERP/Currency/Handler.php
@@ -4,6 +4,7 @@
 
 use Exception;
 use QUI;
+use QUI\Interfaces\Users\User;
 use QUI\Locale;
 
 use function class_exists;
@@ -224,7 +225,7 @@ public static function getDefaultCurrency(): ?Currency
      * @param null|QUI\Interfaces\Users\User $User - optional
      * @return Currency|null
      */
-    public static function getUserCurrency(QUI\Interfaces\Users\User $User = null): ?Currency
+    public static function getUserCurrency(null | QUI\Interfaces\Users\User $User = null): ?Currency
     {
         if ($User === null) {
             $User = QUI::getUserBySession();
@@ -260,10 +261,10 @@ public static function getUserCurrency(QUI\Interfaces\Users\User $User = null):
     /**
      * Return the currency of the user by its country
      *
-     * @param null $User
+     * @param User|null $User
      * @return Currency|null
      */
-    public static function getUserCurrencyByCountry($User = null): ?Currency
+    public static function getUserCurrencyByCountry(null | QUI\Interfaces\Users\User $User = null): ?Currency
     {
         if ($User === null) {
             $User = QUI::getUserBySession();
@@ -366,7 +367,7 @@ public static function getData(): array
      * @return Currency
      * @throws QUI\Exception
      */
-    public static function getCurrency(Currency|string|array $currency): Currency
+    public static function getCurrency(Currency | string | array $currency): Currency
     {
         if ($currency instanceof Currency) {
             return $currency;
diff --git a/tests/phpunit-bootstrap.php b/tests/phpunit-bootstrap.php
new file mode 100644
index 0000000000000000000000000000000000000000..eca92fd67bed8ae4ec424ed82d300119d792f042
--- /dev/null
+++ b/tests/phpunit-bootstrap.php
@@ -0,0 +1,11 @@
+<?php
+
+if (!defined('QUIQQER_SYSTEM')) {
+    define('QUIQQER_SYSTEM', true);
+}
+
+if (!defined('QUIQQER_AJAX')) {
+    define('QUIQQER_AJAX', true);
+}
+
+require_once __DIR__ . '/../../../../bootstrap.php';