From 6ed49300a8a60ed55025db39864ea2dec6579b4d Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 11 Jun 2026 11:44:06 +0000
Subject: [PATCH 1/4] Initial plan


From 696712e1a477d21a3161451df2c44a32af674d7f Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 11 Jun 2026 12:00:49 +0000
Subject: [PATCH 2/4] Set up PHP development infrastructure

---
 .github/workflows/ci.yml                      |   61 -
 .github/workflows/tests.yml                   |   62 +
 composer.json                                 |   43 +-
 examples/config.php.dist                      |    1 +
 examples/tag_admin.php                        |    1 +
 examples/ticket.php                           |    1 +
 examples/user.php                             |    1 +
 phpstan-baseline.neon                         | 1021 +++++++++++++++++
 phpstan.neon.dist                             |    9 +
 phpunit.xml.dist                              |   28 +-
 src/Client.php                                |   49 +-
 src/Client/Response.php                       |   20 +-
 src/Exception/AbstractException.php           |    6 +-
 .../AlreadyFetchedObjectException.php         |    6 +-
 src/HTTPClient.php                            |   60 +-
 src/HTTPClientInterface.php                   |    2 +
 src/Resource/AbstractResource.php             |  156 +--
 src/Resource/Group.php                        |    7 +-
 src/Resource/Link.php                         |   36 +-
 src/Resource/Organization.php                 |   16 +-
 src/Resource/Tag.php                          |   44 +-
 src/Resource/TextModule.php                   |   16 +-
 src/Resource/Ticket.php                       |   17 +-
 src/Resource/TicketArticle.php                |   38 +-
 src/Resource/TicketPriority.php               |    7 +-
 src/Resource/TicketState.php                  |    7 +-
 src/Resource/User.php                         |   16 +-
 src/ResourceType.php                          |   25 +-
 test/ZammadAPIClient/Client/ResponseTest.php  |    1 +
 test/ZammadAPIClient/ClientTest.php           |    7 +
 test/ZammadAPIClient/EnvConfigTrait.php       |    1 +
 test/ZammadAPIClient/GetIDTest.php            |    1 +
 .../Resource/AbstractBaseTest.php             |    5 +-
 test/ZammadAPIClient/Resource/GroupTest.php   |    3 +
 test/ZammadAPIClient/Resource/LinkTest.php    |    3 +
 .../Resource/OrganizationTest.php             |    3 +
 test/ZammadAPIClient/Resource/TagTest.php     |    3 +
 .../Resource/TextModuleTest.php               |    3 +
 .../Resource/TicketArticleTest.php            |    3 +
 .../Resource/TicketPriorityTest.php           |    3 +
 .../Resource/TicketStateTest.php              |    3 +
 test/ZammadAPIClient/Resource/TicketTest.php  |    3 +
 test/ZammadAPIClient/Resource/UserTest.php    |    3 +
 test/bootstrap.php                            |   66 +-
 44 files changed, 1488 insertions(+), 379 deletions(-)
 delete mode 100644 .github/workflows/ci.yml
 create mode 100644 .github/workflows/tests.yml
 create mode 100644 phpstan-baseline.neon
 create mode 100644 phpstan.neon.dist

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
deleted file mode 100644
index 8ac6f90..0000000
--- a/.github/workflows/ci.yml
+++ /dev/null
@@ -1,61 +0,0 @@
-name: CI
-on:
-  push:
-    branches: [master]
-  pull_request:
-  schedule:
-    # Run every on Friday to ensure everything works as expected.
-    - cron:  '0 6 * * 5'
-jobs:
-  CI:
-    runs-on: ubuntu-latest
-    container:
-      image: zammad/zammad-ci:latest
-    services:
-      postgresql:
-        image: postgres:17
-        env:
-          POSTGRES_USER: zammad
-          POSTGRES_PASSWORD: zammad
-      redis:
-        image: redis:7
-    env:
-      ZAMMAD_PHP_API_CLIENT_UNIT_TESTS_URL: "http://localhost:3000"
-      ZAMMAD_PHP_API_CLIENT_UNIT_TESTS_USERNAME: "admin@example.com"
-      ZAMMAD_PHP_API_CLIENT_UNIT_TESTS_PASSWORD: "test"
-    strategy:
-      fail-fast: false
-      matrix:
-        php: ['7.4', '7.3', '7.2', '8.0', '8.1', '8.2', '8.3', '8.4']
-    name: PHP ${{ matrix.php }}
-    steps:
-      - uses: actions/checkout@v6
-      - name: Install PHP
-        uses: shivammathur/setup-php@v2
-        env:
-          fail-fast: true
-        with:
-          php-version: ${{ matrix.php }}
-      - name: Report PHP version
-        run: php -v
-      - name: Install dependencies
-        shell: bash
-        run: |
-          composer install
-      - name: Set up Zammad
-        shell: bash
-        run: |
-          git clone --depth 1 https://github.com/zammad/zammad.git
-          cd zammad
-          source /etc/profile.d/rvm.sh # ensure RVM is loaded
-          bundle config set --local frozen 'true'
-          bundle config set --local path 'vendor'
-          bundle install -j $(nproc)
-          bundle exec ruby .gitlab/configure_environment.rb
-          source .gitlab/environment.env
-          RAILS_ENV=test bundle exec rake db:create
-          RAILS_ENV=test bundle exec rake zammad:ci:test:start zammad:setup:auto_wizard
-      - name: Run PHP API integration tests
-        shell: bash
-        run: |
-          vendor/bin/phpunit
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
new file mode 100644
index 0000000..a4f347d
--- /dev/null
+++ b/.github/workflows/tests.yml
@@ -0,0 +1,62 @@
+name: Tests
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  unit:
+    if: github.event_name != 'workflow_dispatch'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Set up PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.3'
+          tools: composer
+
+      - name: Install dependencies
+        run: composer install --no-interaction --prefer-dist
+
+      - name: Run PHPCS
+        run: vendor/bin/phpcs --standard=PSR12 src/
+
+      - name: Run PHPStan
+        run: vendor/bin/phpstan analyse src/ --configuration phpstan.neon.dist
+
+      - name: Run PHPUnit unit suite
+        run: vendor/bin/phpunit --testsuite unit
+
+  testcontainers:
+    if: github.event_name == 'workflow_dispatch'
+    runs-on: ubuntu-latest
+    services:
+      docker:
+        image: docker:dind
+        options: --privileged
+        ports:
+          - 2375:2375
+    env:
+      DOCKER_HOST: tcp://127.0.0.1:2375
+      DOCKER_TLS_CERTDIR: ''
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Set up PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.3'
+          tools: composer
+
+      - name: Install dependencies
+        run: composer install --no-interaction --prefer-dist
+
+      - name: Verify Docker daemon
+        run: docker info
+
+      - name: Run PHPUnit integration suite
+        run: vendor/bin/phpunit --no-configuration --bootstrap test/bootstrap.php test/ZammadAPIClient/Resource
diff --git a/composer.json b/composer.json
index 60dcdeb..88c6a41 100644
--- a/composer.json
+++ b/composer.json
@@ -3,8 +3,14 @@
     "type": "library",
     "description": "Zammad API client for PHP",
     "homepage": "https://github.com/zammad/zammad-api-client-php",
-    "keywords": ["zammad", "api"],
-    "license": ["AGPL-3.0", "MIT"],
+    "keywords": [
+        "zammad",
+        "api"
+    ],
+    "license": [
+        "AGPL-3.0",
+        "MIT"
+    ],
     "authors": [
         {
             "name": "Zammad GmbH",
@@ -12,13 +18,38 @@
         }
     ],
     "require": {
-        "php":               ">=7.2",
-        "guzzlehttp/guzzle": "^7"
+        "php": ">=8.3",
+        "psr/http-client": "^1.0",
+        "psr/http-factory": "^1.1",
+        "psr/log": "^3.0"
     },
     "require-dev": {
-        "phpunit/phpunit": ">=5.7 <9"
+        "guzzlehttp/guzzle": "^7.11",
+        "league/openapi-psr7-validator": "^0.22",
+        "mockery/mockery": "^1.6",
+        "phpstan/phpstan": "^2.2",
+        "phpunit/phpunit": "^10.5.62",
+        "squizlabs/php_codesniffer": "^3.11"
+    },
+    "suggest": {
+        "guzzlehttp/guzzle": "Provides the default HTTP client implementation used by ZammadAPIClient\\HTTPClient."
     },
     "autoload": {
-        "psr-4": {"ZammadAPIClient\\": "src/"}
+        "psr-4": {
+            "ZammadAPIClient\\": "src/"
+        }
+    },
+    "autoload-dev": {
+        "classmap": [
+            "test/"
+        ]
+    },
+    "scripts": {
+        "phpcs": "phpcs --standard=PSR12 src/",
+        "phpstan": "phpstan analyse src/ --configuration phpstan.neon.dist",
+        "test": "phpunit --testsuite=unit"
+    },
+    "config": {
+        "sort-packages": true
     }
 }
diff --git a/examples/config.php.dist b/examples/config.php.dist
index e9564ef..3db3140 100644
--- a/examples/config.php.dist
+++ b/examples/config.php.dist
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 // Copy this file to config.php and insert your credentials.
 // Note that you have to activate API access within your Zammad (Settings => System => API)
diff --git a/examples/tag_admin.php b/examples/tag_admin.php
index 6150af9..f805630 100644
--- a/examples/tag_admin.php
+++ b/examples/tag_admin.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 /**
  * Example for Tag administration scope.
diff --git a/examples/ticket.php b/examples/ticket.php
index 21c9a95..4ef957b 100644
--- a/examples/ticket.php
+++ b/examples/ticket.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 require __DIR__ . '/../vendor/autoload.php';
 require __DIR__ . '/config.php';
diff --git a/examples/user.php b/examples/user.php
index c07cb18..b9b0cc5 100644
--- a/examples/user.php
+++ b/examples/user.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 require __DIR__ . '/../vendor/autoload.php';
 require __DIR__ . '/config.php';
diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
new file mode 100644
index 0000000..a040334
--- /dev/null
+++ b/phpstan-baseline.neon
@@ -0,0 +1,1021 @@
+parameters:
+	ignoreErrors:
+		-
+			message: '#^Call to an undefined method object\:\:getBody\(\)\.$#'
+			identifier: method.notFound
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Call to an undefined method object\:\:getHeaders\(\)\.$#'
+			identifier: method.notFound
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Call to an undefined method object\:\:getReasonPhrase\(\)\.$#'
+			identifier: method.notFound
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Call to an undefined method object\:\:getStatusCode\(\)\.$#'
+			identifier: method.notFound
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Cannot access offset ''Accept'' on mixed\.$#'
+			identifier: offsetAccess.nonOffsetAccessible
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Cannot access offset ''Content\-Type'' on mixed\.$#'
+			identifier: offsetAccess.nonOffsetAccessible
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Cannot access offset ''From'' on mixed\.$#'
+			identifier: offsetAccess.nonOffsetAccessible
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Cannot call method request\(\) on mixed\.$#'
+			identifier: method.nonObject
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:__construct\(\) has parameter \$options with no value type specified in iterable type array\.$#'
+			identifier: missingType.iterableValue
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:delete\(\) has parameter \$data with no value type specified in iterable type array\.$#'
+			identifier: missingType.iterableValue
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:delete\(\) has parameter \$url_parameters with no value type specified in iterable type array\.$#'
+			identifier: missingType.iterableValue
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:get\(\) has parameter \$url_parameters with no value type specified in iterable type array\.$#'
+			identifier: missingType.iterableValue
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:getLastResponse\(\) has invalid return type ZammadAPIClient\\objects\.$#'
+			identifier: class.notFound
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:getLastResponse\(\) should return ZammadAPIClient\\objects but returns mixed\.$#'
+			identifier: return.type
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:post\(\) has parameter \$data with no value type specified in iterable type array\.$#'
+			identifier: missingType.iterableValue
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:post\(\) has parameter \$url_parameters with no value type specified in iterable type array\.$#'
+			identifier: missingType.iterableValue
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:put\(\) has parameter \$data with no value type specified in iterable type array\.$#'
+			identifier: missingType.iterableValue
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:put\(\) has parameter \$url_parameters with no value type specified in iterable type array\.$#'
+			identifier: missingType.iterableValue
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:request\(\) has parameter \$options with no value type specified in iterable type array\.$#'
+			identifier: missingType.iterableValue
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:request\(\) has parameter \$url_parameters with no value type specified in iterable type array\.$#'
+			identifier: missingType.iterableValue
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:setLastResponse\(\) has no return type specified\.$#'
+			identifier: missingType.return
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:setOnBehalfOfUser\(\) has no return type specified\.$#'
+			identifier: missingType.return
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\:\:unsetOnBehalfOfUser\(\) has no return type specified\.$#'
+			identifier: missingType.return
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^PHPDoc tag @param for parameter \$response with type object is not subtype of native type ZammadAPIClient\\Client\\Response\.$#'
+			identifier: parameter.phpDocType
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Parameter \#4 \$headers of class ZammadAPIClient\\Client\\Response constructor expects array, mixed given\.$#'
+			identifier: argument.type
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Property ZammadAPIClient\\Client\:\:\$http_client has no type specified\.$#'
+			identifier: missingType.property
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Property ZammadAPIClient\\Client\:\:\$last_response has no type specified\.$#'
+			identifier: missingType.property
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Property ZammadAPIClient\\Client\:\:\$on_behalf_of_user has no type specified\.$#'
+			identifier: missingType.property
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Property ZammadAPIClient\\Client\:\:\$options has no type specified\.$#'
+			identifier: missingType.property
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Property ZammadAPIClient\\Client\:\:\$options is never read, only written\.$#'
+			identifier: property.onlyWritten
+			count: 1
+			path: src/Client.php
+
+		-
+			message: '#^Binary operation "\." between mixed and '' \- '' results in an error\.$#'
+			identifier: binaryOp.invalid
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Binary operation "\." between non\-falsy\-string and mixed results in an error\.$#'
+			identifier: binaryOp.invalid
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Cannot access offset ''error'' on mixed\.$#'
+			identifier: offsetAccess.nonOffsetAccessible
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Cannot access offset 0 on mixed\.$#'
+			identifier: offsetAccess.nonOffsetAccessible
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\\Response\:\:__construct\(\) has parameter \$body with no type specified\.$#'
+			identifier: missingType.parameter
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\\Response\:\:__construct\(\) has parameter \$headers with no value type specified in iterable type array\.$#'
+			identifier: missingType.iterableValue
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\\Response\:\:__construct\(\) has parameter \$reason_phrase with no type specified\.$#'
+			identifier: missingType.parameter
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\\Response\:\:__construct\(\) has parameter \$status_code with no type specified\.$#'
+			identifier: missingType.parameter
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\\Response\:\:getBody\(\) has no return type specified\.$#'
+			identifier: missingType.return
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\\Response\:\:getData\(\) has no return type specified\.$#'
+			identifier: missingType.return
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\\Response\:\:getError\(\) has no return type specified\.$#'
+			identifier: missingType.return
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\\Response\:\:getHeaders\(\) has no return type specified\.$#'
+			identifier: missingType.return
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\\Response\:\:getReasonPhrase\(\) has no return type specified\.$#'
+			identifier: missingType.return
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\\Response\:\:getStatusCode\(\) has no return type specified\.$#'
+			identifier: missingType.return
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\\Response\:\:getStatusMessage\(\) has no return type specified\.$#'
+			identifier: missingType.return
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Method ZammadAPIClient\\Client\\Response\:\:hasError\(\) has no return type specified\.$#'
+			identifier: missingType.return
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Parameter \#1 \$haystack of function mb_strpos expects string, mixed given\.$#'
+			identifier: argument.type
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Parameter \#1 \$json of function json_decode expects string, mixed given\.$#'
+			identifier: argument.type
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Parameter \#1 \$value of function intval expects array\|bool\|float\|GMP\|int\|resource\|SimpleXMLElement\|string\|null, mixed given\.$#'
+			identifier: argument.type
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Property ZammadAPIClient\\Client\\Response\:\:\$body has no type specified\.$#'
+			identifier: missingType.property
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Property ZammadAPIClient\\Client\\Response\:\:\$data has no type specified\.$#'
+			identifier: missingType.property
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Property ZammadAPIClient\\Client\\Response\:\:\$error has no type specified\.$#'
+			identifier: missingType.property
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Property ZammadAPIClient\\Client\\Response\:\:\$headers has no type specified\.$#'
+			identifier: missingType.property
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Property ZammadAPIClient\\Client\\Response\:\:\$reason_phrase has no type specified\.$#'
+			identifier: missingType.property
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Property ZammadAPIClient\\Client\\Response\:\:\$status_code has no type specified\.$#'
+			identifier: missingType.property
+			count: 1
+			path: src/Client/Response.php
+
+		-
+			message: '#^Binary operation "\." between ''Bearer '' and mixed results in an error\.$#'
+			identifier: binaryOp.invalid
+			count: 1
+			path: src/HTTPClient.php
+
+		-
+			message: '#^Binary operation "\." between ''Token token\='' and mixed results in an error\.$#'
+			identifier: binaryOp.invalid
+			count: 1
+			path: src/HTTPClient.php
+
+		-
+			message: '#^Binary operation "\." between mixed and ''/api/'' results in an error\.$#'
+			identifier: binaryOp.invalid
+			count: 1
+			path: src/HTTPClient.php
+
+		-
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+		-
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+
+		-
+			message: '#^Parameter \#1 \$remote_data of method ZammadAPIClient\\Resource\\AbstractResource\:\:setRemoteData\(\) expects array, mixed given\.$#'
+			identifier: argument.type
+			count: 1
+			path: src/Resource/User.php
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
new file mode 100644
index 0000000..fe173aa
--- /dev/null
+++ b/phpstan.neon.dist
@@ -0,0 +1,9 @@
+includes:
+    - phpstan-baseline.neon
+
+parameters:
+    bootstrapFiles:
+        - test/bootstrap.php
+    level: max
+    paths:
+        - src
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 2cd5e9e..bbb9b29 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,20 +1,24 @@
 <?xml version="1.0" encoding="UTF-8"?>
-
-<phpunit backupGlobals="false"
-         backupStaticAttributes="false"
-         colors="true"
-         convertErrorsToExceptions="true"
-         convertNoticesToExceptions="true"
-         convertWarningsToExceptions="true"
-         processIsolation="false"
-         stopOnFailure="false"
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
          bootstrap="test/bootstrap.php"
-    >
+         cacheResult="false"
+         colors="true">
     <testsuites>
-        <testsuite name="zammad-api-client-php Test Suite">
-            <directory>./test/</directory>
+        <testsuite name="unit">
+            <directory>test/ZammadAPIClient</directory>
+            <exclude>test/ZammadAPIClient/Resource</exclude>
+        </testsuite>
+        <testsuite name="integration">
+            <directory>test/ZammadAPIClient/Resource</directory>
         </testsuite>
     </testsuites>
+    <groups>
+        <exclude>
+            <group>integration</group>
+            <group>testcontainers</group>
+        </exclude>
+    </groups>
     <php>
         <!-- Note: unit tests are only possible via username and password -->
         <!--
diff --git a/src/Client.php b/src/Client.php
index 835195a..ef5c760 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -1,9 +1,6 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient;
 
@@ -11,7 +8,7 @@
 
 class Client
 {
-    const API_VERSION = 'v1';
+    public const API_VERSION = 'v1';
 
     private $http_client;
     private $last_response;
@@ -46,10 +43,24 @@ class Client
      *
      * @return Object                           Client object
      */
-    public function __construct( array $options = [], ?HTTPClientInterface $client = null)
+    public function __construct(array $options = [], ?HTTPClientInterface $client = null)
     {
-        $this->options     = $options;
-        $this->http_client = $client ?? new HTTPClient($options);
+        $this->options = $options;
+
+        if ($client !== null) {
+            $this->http_client = $client;
+
+            return;
+        }
+
+        if (!class_exists(\GuzzleHttp\Client::class)) {
+            throw new \RuntimeException(
+                'No default HTTP client is available. '
+                . 'Install guzzlehttp/guzzle or pass a custom HTTPClientInterface implementation.'
+            );
+        }
+
+        $this->http_client = new HTTPClient($options);
     }
 
     /**
@@ -61,12 +72,12 @@ public function __construct( array $options = [], ?HTTPClientInterface $client =
      *
      * @return Response object
      */
-    private function request ( $method, $url, array $url_parameters = [], array $options = [] )
+    private function request($method, $url, array $url_parameters = [], array $options = [])
     {
         $method = mb_strtoupper($method);
 
         if (!empty($url_parameters)) {
-          $options['query'] = $url_parameters;
+            $options['query'] = $url_parameters;
         }
 
         // Set JSON headers
@@ -74,12 +85,12 @@ private function request ( $method, $url, array $url_parameters = [], array $opt
         $options['headers']['Content-Type'] = 'application/json; charset=utf-8';
 
         // Set "on behalf of user" header (X-On-Behalf-Of was deprecated in Zammad 6.5 in favor of From)
-        if ( !empty($this->on_behalf_of_user) ) {
+        if (!empty($this->on_behalf_of_user)) {
             $options['headers']['From'] = $this->on_behalf_of_user;
         }
 
-        $http_client_response = $this->http_client->request( $method, $url, $options );
-        if ( !is_object($http_client_response) ) {
+        $http_client_response = $this->http_client->request($method, $url, $options);
+        if (!is_object($http_client_response)) {
             throw new \RuntimeException('Unable to create HTTP client request.');
         }
 
@@ -104,7 +115,7 @@ private function request ( $method, $url, array $url_parameters = [], array $opt
      *
      * @return Response object
      */
-    public function get( $url, array $url_parameters = [] )
+    public function get($url, array $url_parameters = [])
     {
         $response = $this->request(
             'GET',
@@ -124,7 +135,7 @@ public function get( $url, array $url_parameters = [] )
      *
      * @return Response object
      */
-    public function post( $url, array $data = [], array $url_parameters = [] )
+    public function post($url, array $data = [], array $url_parameters = [])
     {
         $response = $this->request(
             'POST',
@@ -145,7 +156,7 @@ public function post( $url, array $data = [], array $url_parameters = [] )
      *
      * @return Response object
      */
-    public function put( $url, array $data = [], array $url_parameters = [] )
+    public function put($url, array $data = [], array $url_parameters = [])
     {
         $response = $this->request(
             'PUT',
@@ -165,10 +176,10 @@ public function put( $url, array $data = [], array $url_parameters = [] )
      *
      * @return Response object
      */
-    public function delete( $url, array $url_parameters = [], array $data = [] )
+    public function delete($url, array $url_parameters = [], array $data = [])
     {
         $options = [];
-        if ( !empty($data) ) {
+        if (!empty($data)) {
             $options['json'] = $data;
         }
 
@@ -220,7 +231,7 @@ public function unsetOnBehalfOfUser()
      *
      * @param Object $response              Response object to store.
      */
-    private function setLastResponse( Response $response )
+    private function setLastResponse(Response $response)
     {
         $this->last_response = $response;
     }
diff --git a/src/Client/Response.php b/src/Client/Response.php
index fedfa70..96f3da3 100644
--- a/src/Client/Response.php
+++ b/src/Client/Response.php
@@ -1,9 +1,6 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Client;
 
@@ -20,9 +17,8 @@ public function __construct(
         $status_code,
         $reason_phrase,
         $body,
-        array  $headers = []
-    )
-    {
+        array $headers = []
+    ) {
         $this->status_code   = intval($status_code);
         $this->reason_phrase = $reason_phrase;
         $this->body          = $body;
@@ -33,12 +29,12 @@ public function __construct(
 
         // Store decoded JSON data, if present
         if (
-            !empty( $lowercase_headers['content-type'] )
-            && mb_strpos( $lowercase_headers['content-type'][0], 'application/json;' ) !== false
+            !empty($lowercase_headers['content-type'])
+            && mb_strpos($lowercase_headers['content-type'][0], 'application/json;') !== false
         ) {
-            $this->data = json_decode( $this->body, true );
+            $this->data = json_decode($this->body, true);
 
-            if ( !empty( $this->data['error'] ) ) {
+            if (!empty($this->data['error'])) {
                 $this->error = $this->data['error'];
             }
         }
@@ -81,6 +77,6 @@ public function getError()
 
     public function hasError()
     {
-        return !empty( $this->getError() );
+        return !empty($this->getError());
     }
 }
diff --git a/src/Exception/AbstractException.php b/src/Exception/AbstractException.php
index 1dfce30..e093a8c 100644
--- a/src/Exception/AbstractException.php
+++ b/src/Exception/AbstractException.php
@@ -1,13 +1,9 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Exception;
 
 abstract class AbstractException extends \Exception
 {
-
 }
diff --git a/src/Exception/AlreadyFetchedObjectException.php b/src/Exception/AlreadyFetchedObjectException.php
index 573a160..edfa70f 100644
--- a/src/Exception/AlreadyFetchedObjectException.php
+++ b/src/Exception/AlreadyFetchedObjectException.php
@@ -1,13 +1,9 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Exception;
 
 class AlreadyFetchedObjectException extends AbstractException
 {
-
 }
diff --git a/src/HTTPClient.php b/src/HTTPClient.php
index 08531a7..f5b3254 100644
--- a/src/HTTPClient.php
+++ b/src/HTTPClient.php
@@ -1,9 +1,6 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient;
 
@@ -44,32 +41,31 @@ class HTTPClient extends \GuzzleHttp\Client implements HTTPClientInterface
      *
      * @return Object                           HTTPClient object
      */
-    public function __construct( array $options = [] )
+    public function __construct(array $options = [])
     {
         //
         // Check options
         //
 
         // URL
-        if ( empty( $options['url'] ) ) {
+        if (empty($options['url'])) {
             throw new \RuntimeException('Missing option "url"');
         }
-        $url_components = parse_url( $options['url'] );
+        $url_components = parse_url($options['url']);
         if (
             $url_components === false
-            || empty( $url_components['scheme'] )
-            || empty( $url_components['host'] )
+            || empty($url_components['scheme'])
+            || empty($url_components['host'])
         ) {
             throw new \RuntimeException('Invalid URL');
         }
 
         // Authentication
         $number_of_authentication_types_given = 0;
-        if ( !empty( $options['username'] ) || !empty( $options['password'] ) ) {
-            if ( empty( $options['username'] ) ) {
+        if (!empty($options['username']) || !empty($options['password'])) {
+            if (empty($options['username'])) {
                 throw new \RuntimeException('Missing option "username"');
-            }
-            else if ( empty( $options['password'] ) ) {
+            } elseif (empty($options['password'])) {
                 throw new \RuntimeException('Missing option "password"');
             }
 
@@ -81,7 +77,7 @@ public function __construct( array $options = [] )
             ];
         }
 
-        if ( !empty( $options['http_token'] ) ) {
+        if (!empty($options['http_token'])) {
             $number_of_authentication_types_given++;
 
             $this->authentication_options = [
@@ -89,7 +85,7 @@ public function __construct( array $options = [] )
             ];
         }
 
-        if ( !empty( $options['oauth2_token'] ) ) {
+        if (!empty($options['oauth2_token'])) {
             $number_of_authentication_types_given++;
 
             $this->authentication_options = [
@@ -97,8 +93,11 @@ public function __construct( array $options = [] )
             ];
         }
 
-        if ( $number_of_authentication_types_given != 1 ) {
-            throw new \RuntimeException('Missing authentication options: Either give username/password, http_token or oauth2_token');
+        if ($number_of_authentication_types_given != 1) {
+            throw new \RuntimeException(
+                'Missing authentication options: Either give username/password, ' .
+                'http_token or oauth2_token'
+            );
         }
 
         // Assemble base URL
@@ -106,7 +105,7 @@ public function __construct( array $options = [] )
 
         // Optional: override timeout
         $timeout = 5;
-        if ( array_key_exists( 'timeout', $options ) ) {
+        if (array_key_exists('timeout', $options)) {
             $timeout = intval($options['timeout']);
             if ($timeout < 0) {
                 $timeout = 0;
@@ -115,7 +114,7 @@ public function __construct( array $options = [] )
 
         // Debug flag
         $debug = false;
-        if ( array_key_exists( 'debug', $options ) ) {
+        if (array_key_exists('debug', $options)) {
             $debug = $options['debug'] ? true : false;
         }
 
@@ -155,40 +154,33 @@ public function __construct( array $options = [] )
     /**
      * Overrides base class request method to automatically add authentication options to request.
      */
-    public function request(string $method, $uri = '', array $options = [] ): ResponseInterface
+    public function request(string $method, $uri = '', array $options = []): ResponseInterface
     {
         //
         // Add authentication options
         //
 
-        // Username and password
         if (
-            !empty( $this->authentication_options['username'] )
-            && !empty( $this->authentication_options['password'] )
+            !empty($this->authentication_options['username'])
+            && !empty($this->authentication_options['password'])
         ) {
             $options['auth'] = [
                 $this->authentication_options['username'],
                 $this->authentication_options['password'],
             ];
-        }
-        // HTTP token
-        else if ( !empty( $this->authentication_options['http_token'] ) ) {
+        } elseif (!empty($this->authentication_options['http_token'])) {
             $options['headers']['Authorization']
                 = 'Token token=' . $this->authentication_options['http_token'];
-        }
-        // OAuth2 token
-        else if ( !empty( $this->authentication_options['oauth2_token'] ) ) {
+        } elseif (!empty($this->authentication_options['oauth2_token'])) {
             $options['headers']['Authorization']
                 = 'Bearer ' . $this->authentication_options['oauth2_token'];
-        }
-        else {
+        } else {
             throw new \RuntimeException('No authentication options available');
         }
 
         try {
-            $response = parent::request( $method, $uri, $options );
-        }
-        catch ( \GuzzleHttp\Exception\TransferException $e ) {
+            $response = parent::request($method, $uri, $options);
+        } catch (\GuzzleHttp\Exception\TransferException $e) {
             if (method_exists($e, 'hasResponse') && $e->hasResponse()) {
                 return $e->getResponse();
             }
diff --git a/src/HTTPClientInterface.php b/src/HTTPClientInterface.php
index 870d224..fd41918 100644
--- a/src/HTTPClientInterface.php
+++ b/src/HTTPClientInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace ZammadAPIClient;
 
 use Psr\Http\Message\ResponseInterface;
diff --git a/src/Resource/AbstractResource.php b/src/Resource/AbstractResource.php
index 60478f9..c39b84e 100644
--- a/src/Resource/AbstractResource.php
+++ b/src/Resource/AbstractResource.php
@@ -1,9 +1,6 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
@@ -26,7 +23,7 @@ abstract class AbstractResource
     /**
      * @param object $client        ZammadAPIClient object
      */
-    public function __construct( \ZammadAPIClient\Client $client )
+    public function __construct(\ZammadAPIClient\Client $client)
     {
         $this->client = $client;
     }
@@ -48,7 +45,7 @@ protected function getClient()
      *
      * @return object
      */
-    protected function setRemoteData( array $remote_data = [] )
+    protected function setRemoteData(array $remote_data = [])
     {
         $this->remote_data = $remote_data;
         return $this;
@@ -86,9 +83,9 @@ protected function getRemoteData()
      *
      * @return object   This object
      */
-    public function setValues( array $values )
+    public function setValues(array $values)
     {
-        $this->values = array_merge( $this->values, $values );
+        $this->values = array_merge($this->values, $values);
         return $this;
     }
 
@@ -100,7 +97,7 @@ public function setValues( array $values )
      *
      * @return object   This object
      */
-    public function setValue( $key, $value )
+    public function setValue($key, $value)
     {
         $this->values[$key] = $value;
         return $this;
@@ -121,12 +118,12 @@ public function setValue( $key, $value )
      */
     public function getValue($key)
     {
-        if ( array_key_exists( $key, $this->values ) ) {
+        if (array_key_exists($key, $this->values)) {
             return $this->values[$key];
         }
 
         $remote_data = $this->getRemoteData();
-        if ( array_key_exists( $key, $remote_data ) ) {
+        if (array_key_exists($key, $remote_data)) {
             return $remote_data[$key];
         }
 
@@ -143,7 +140,7 @@ public function getValue($key)
      */
     public function getValues()
     {
-        $values = array_merge( $this->getRemoteData(), $this->values );
+        $values = array_merge($this->getRemoteData(), $this->values);
         return $values;
     }
 
@@ -188,7 +185,7 @@ public function getID()
      */
     public function isDirty()
     {
-        return !empty( $this->getUnsavedValues() );
+        return !empty($this->getUnsavedValues());
     }
 
     /**
@@ -198,7 +195,7 @@ public function isDirty()
      *
      * @return object   This object
      */
-    protected function setError( $error )
+    protected function setError($error)
     {
         $this->error = $error;
         return $this;
@@ -221,7 +218,7 @@ public function getError()
      */
     public function hasError()
     {
-        return !empty( $this->getError() );
+        return !empty($this->getError());
     }
 
     /**
@@ -244,11 +241,13 @@ protected function clearError()
      */
     public function get($object_id)
     {
-        if ( !empty( $this->getValues() ) ) {
-            throw new AlreadyFetchedObjectException('Object already contains values, get() not possible, use a new object');
+        if (!empty($this->getValues())) {
+            throw new AlreadyFetchedObjectException(
+                'Object already contains values, get() not possible, use a new object'
+            );
         }
 
-        if ( empty($object_id) ) {
+        if (empty($object_id)) {
             throw new \RuntimeException('Missing object ID');
         }
 
@@ -266,12 +265,11 @@ public function get($object_id)
             ]
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
-        }
-        else {
+        if ($response->hasError()) {
+            $this->setError($response->getError());
+        } else {
             $this->clearError();
-            $this->setRemoteData( $response->getData() );
+            $this->setRemoteData($response->getData());
         }
 
         return $this;
@@ -287,16 +285,18 @@ public function get($object_id)
      * @return mixed                        Returns array of ZammadAPIClient\Resource\... objects
      *                                          or this object on failure.
      */
-    public function all( $page = null, $objects_per_page = null )
+    public function all($page = null, $objects_per_page = null)
     {
-        if ( !empty( $this->getValues() ) ) {
-            throw new AlreadyFetchedObjectException('Object already contains values, all() not possible, use a new object');
+        if (!empty($this->getValues())) {
+            throw new AlreadyFetchedObjectException(
+                'Object already contains values, all() not possible, use a new object'
+            );
         }
 
-        if ( isset($page) && $page <= 0 ) {
+        if (isset($page) && $page <= 0) {
             throw new \RuntimeException('Parameter page must be > 0');
         }
-        if ( isset($objects_per_page) && $objects_per_page <= 0 ) {
+        if (isset($objects_per_page) && $objects_per_page <= 0) {
             throw new \RuntimeException('Parameter objects_per_page must be > 0');
         }
         if (
@@ -306,7 +306,7 @@ public function all( $page = null, $objects_per_page = null )
             throw new \RuntimeException('Parameters page and objects_per_page must both be given');
         }
 
-        if ( !isset($page) || !isset($objects_per_page) ) {
+        if (!isset($page) || !isset($objects_per_page)) {
             return $this->allWithoutPagination();
         }
 
@@ -314,7 +314,7 @@ public function all( $page = null, $objects_per_page = null )
             'expand' => true,
         ];
 
-        if ( isset($page) && isset($objects_per_page) ) {
+        if (isset($page) && isset($objects_per_page)) {
             $url_parameters['page']     = $page;
             $url_parameters['per_page'] = $objects_per_page;
         }
@@ -325,8 +325,8 @@ public function all( $page = null, $objects_per_page = null )
             $url_parameters
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
+        if ($response->hasError()) {
+            $this->setError($response->getError());
             return $this;
         }
 
@@ -335,8 +335,8 @@ public function all( $page = null, $objects_per_page = null )
         // Return array of resource objects if no $object_id was given.
         // Note: the resource object (this object) used to execute get() will be left empty in this case.
         $objects       = [];
-        foreach ( $response->getData() as $object_data ) {
-            $object = $this->getClient()->resource( get_class($this) );
+        foreach ($response->getData() as $object_data) {
+            $object = $this->getClient()->resource(get_class($this));
             $object->setRemoteData($object_data);
             $objects[] = $object;
         }
@@ -360,18 +360,18 @@ private function allWithoutPagination()
         $objects_of_page  = [];
 
         do {
-            $objects_of_page = $this->all( $page, $objects_per_page );
-            if ( !is_array($objects_of_page) ) {
+            $objects_of_page = $this->all($page, $objects_per_page);
+            if (!is_array($objects_of_page)) {
                 return $this;
             }
 
-            $objects = array_merge( $objects, $objects_of_page );
+            $objects = array_merge($objects, $objects_of_page);
 
             $is_last_page = count($objects_of_page) < $objects_per_page
                 || !count($objects_of_page);
 
             $page++;
-        } while ( !$is_last_page );
+        } while (!$is_last_page);
 
         return $objects;
     }
@@ -389,16 +389,18 @@ private function allWithoutPagination()
      * @return mixed                        Returns array of ZammadAPIClient\Resource\... objects
      *                                          or this object on failure.
      */
-    public function search( $search_term, $page = null, $objects_per_page = null, $sort_by = null, $order_by = null )
+    public function search($search_term, $page = null, $objects_per_page = null, $sort_by = null, $order_by = null)
     {
-        if ( !empty( $this->getValues() ) ) {
-            throw new AlreadyFetchedObjectException('Object already contains values, search() not possible, use a new object');
+        if (!empty($this->getValues())) {
+            throw new AlreadyFetchedObjectException(
+                'Object already contains values, search() not possible, use a new object'
+            );
         }
 
-        if ( isset($page) && $page <= 0 ) {
+        if (isset($page) && $page <= 0) {
             throw new \RuntimeException('Parameter page must be a > 0');
         }
-        if ( isset($objects_per_page) && $objects_per_page <= 0 ) {
+        if (isset($objects_per_page) && $objects_per_page <= 0) {
             throw new \RuntimeException('Parameter objects_per_page must be a > 0');
         }
         if (
@@ -408,11 +410,11 @@ public function search( $search_term, $page = null, $objects_per_page = null, $s
             throw new \RuntimeException('Parameters page and objects_per_page must both be given');
         }
 
-        if ( isset($order_by) && !in_array( mb_strtolower($order_by), [ 'asc', 'desc' ] ) ) {
+        if (isset($order_by) && !in_array(mb_strtolower($order_by), [ 'asc', 'desc' ])) {
             throw new \RuntimeException('Parameter order_by must be "asc" or "desc"');
         }
 
-        if ( !isset($page) || !isset($objects_per_page) ) {
+        if (!isset($page) || !isset($objects_per_page)) {
             return $this->searchWithoutPagination($search_term, $sort_by, $order_by);
         }
 
@@ -421,15 +423,15 @@ public function search( $search_term, $page = null, $objects_per_page = null, $s
             'query'  => $search_term,
         ];
 
-        if ( isset($page) && isset($objects_per_page) ) {
+        if (isset($page) && isset($objects_per_page)) {
             $url_parameters['page']     = $page;
             $url_parameters['per_page'] = $objects_per_page;
         }
 
-        if ( isset($sort_by) ) {
+        if (isset($sort_by)) {
             $url_parameters['sort_by'] = $sort_by;
         }
-        if ( isset($order_by) ) {
+        if (isset($order_by)) {
             $url_parameters['order_by'] = $order_by;
         }
 
@@ -439,8 +441,8 @@ public function search( $search_term, $page = null, $objects_per_page = null, $s
             $url_parameters
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
+        if ($response->hasError()) {
+            $this->setError($response->getError());
             return $this;
         }
 
@@ -449,8 +451,8 @@ public function search( $search_term, $page = null, $objects_per_page = null, $s
         // Return array of resource objects if no $object_id was given.
         // Note: the resource object (this object) used to execute get() will be left empty in this case.
         $objects = [];
-        foreach ( $response->getData() as $object_data ) {
-            $object = $this->getClient()->resource( get_class($this) );
+        foreach ($response->getData() as $object_data) {
+            $object = $this->getClient()->resource(get_class($this));
             $object->setRemoteData($object_data);
             $objects[] = $object;
         }
@@ -478,18 +480,18 @@ private function searchWithoutPagination($search_term, $sort_by = null, $order_b
         $objects_of_page  = [];
 
         do {
-            $objects_of_page = $this->search( $search_term, $page, $objects_per_page, $sort_by, $order_by );
-            if ( !is_array($objects_of_page) ) {
+            $objects_of_page = $this->search($search_term, $page, $objects_per_page, $sort_by, $order_by);
+            if (!is_array($objects_of_page)) {
                 return $this;
             }
 
-            $objects = array_merge( $objects, $objects_of_page );
+            $objects = array_merge($objects, $objects_of_page);
 
             $is_last_page = count($objects_of_page) < $objects_per_page
                 || !count($objects_of_page);
 
             $page++;
-        } while ( !$is_last_page );
+        } while (!$is_last_page);
 
         return $objects;
     }
@@ -501,7 +503,7 @@ private function searchWithoutPagination($search_term, $sort_by = null, $order_b
      */
     public function save()
     {
-        if ( empty( $this->getID() ) ) {
+        if (empty($this->getID())) {
             return $this->create();
         }
 
@@ -515,11 +517,11 @@ public function save()
      */
     protected function create()
     {
-        if ( !empty( $this->getID() ) ) {
+        if (!empty($this->getID())) {
             throw new \Exception('Object already has an ID, create() not possible');
         }
 
-        if ( !$this->isDirty() ) {
+        if (!$this->isDirty()) {
             return $this;
         }
 
@@ -530,14 +532,14 @@ protected function create()
             [
                 'expand' => true,
             ]
-         );
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
+        );
+        if ($response->hasError()) {
+            $this->setError($response->getError());
             return $this;
         }
 
         $this->clearError();
-        $this->setRemoteData( $response->getData() );
+        $this->setRemoteData($response->getData());
         $this->clearUnsavedValues();
 
         return $this;
@@ -551,11 +553,11 @@ protected function create()
     protected function update()
     {
         $object_id = $this->getID();
-        if ( empty($object_id) ) {
+        if (empty($object_id)) {
             throw new \Exception('Object has no ID, update() not possible');
         }
 
-        if ( !$this->isDirty() ) {
+        if (!$this->isDirty()) {
             return $this;
         }
 
@@ -573,13 +575,13 @@ protected function update()
                 'expand' => true,
             ]
         );
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
+        if ($response->hasError()) {
+            $this->setError($response->getError());
             return $this;
         }
 
         $this->clearError();
-        $this->setRemoteData( $response->getData() );
+        $this->setRemoteData($response->getData());
         $this->clearUnsavedValues();
 
         return $this;
@@ -595,7 +597,7 @@ public function delete()
     {
         // Delete object in Zammad.
         $object_id = $this->getID();
-        if ( !empty($object_id) ) {
+        if (!empty($object_id)) {
             $url = $this->getURL(
                 'delete',
                 [
@@ -609,8 +611,8 @@ public function delete()
                     'expand' => true,
                 ]
             );
-            if ( $response->hasError() ) {
-                $this->setError( $response->getError() );
+            if ($response->hasError()) {
+                $this->setError($response->getError());
                 return $this;
             }
         }
@@ -633,9 +635,9 @@ public function delete()
      *
      * @return string                           URL, e. g. 'tickets/10'.
      */
-    protected function getURL( $method_name, array $placeholder_values = [] )
+    protected function getURL($method_name, array $placeholder_values = [])
     {
-        if ( !array_key_exists( $method_name, $this::URLS ) ) {
+        if (!array_key_exists($method_name, $this::URLS)) {
             throw new \RuntimeException(
                 "Method '$method_name' is not supported for "
                 . get_class($this)
@@ -644,15 +646,15 @@ protected function getURL( $method_name, array $placeholder_values = [] )
         }
 
         $url = $this::URLS[$method_name];
-        foreach ( $placeholder_values as $placeholder => $value ) {
-            $url = preg_replace( "/\{$placeholder\}/", "$value", $url );
+        foreach ($placeholder_values as $placeholder => $value) {
+            $url = preg_replace("/\{$placeholder\}/", "$value", $url);
         }
 
         return $url;
     }
 
-    public function can( $method_name )
+    public function can($method_name)
     {
-        return array_key_exists( $method_name, $this::URLS );
+        return array_key_exists($method_name, $this::URLS);
     }
 }
diff --git a/src/Resource/Group.php b/src/Resource/Group.php
index 52f8d84..636b1da 100644
--- a/src/Resource/Group.php
+++ b/src/Resource/Group.php
@@ -1,15 +1,12 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
 class Group extends AbstractResource
 {
-    const URLS = [
+    public const URLS = [
         'get'    => 'groups/{object_id}',
         'all'    => 'groups',
         'create' => 'groups',
diff --git a/src/Resource/Link.php b/src/Resource/Link.php
index a6db72b..5efa1b6 100644
--- a/src/Resource/Link.php
+++ b/src/Resource/Link.php
@@ -1,21 +1,18 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Fran Rey <franreycastedo@gmail.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
 class Link extends AbstractResource
 {
-    const URLS = [
+    public const URLS = [
         'get'    => 'links',
         'add'    => 'links/add',
         'remove' => 'links/remove'
     ];
 
-    const LINKTYPES = [
+    public const LINKTYPES = [
         'normal',
         'parent',
         'child'
@@ -34,7 +31,7 @@ public function get($object_id, $object_type = 'Ticket')
         $this->clearError();
 
         $object_id = intval($object_id);
-        if ( empty($object_id) ) {
+        if (empty($object_id)) {
             throw new \RuntimeException('Missing object ID');
         }
 
@@ -46,12 +43,11 @@ public function get($object_id, $object_type = 'Ticket')
             ]
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
-        }
-        else {
+        if ($response->hasError()) {
+            $this->setError($response->getError());
+        } else {
             $this->clearError();
-            $this->setRemoteData( $response->getData() );
+            $this->setRemoteData($response->getData());
         }
 
         return $this;
@@ -70,11 +66,11 @@ public function add(Ticket $source, Ticket $target, $type = 'normal')
     {
         $this->clearError();
 
-        if ( empty($source->getID()) || empty($target->getID()) ) {
+        if (empty($source->getID()) || empty($target->getID())) {
             $this->setError('Tickets not valid.');
             return $this;
         }
-        if ( !in_array($type, self::LINKTYPES, true) ) {
+        if (!in_array($type, self::LINKTYPES, true)) {
             $this->setError('Linktype is not supported.');
             return $this;
         }
@@ -90,8 +86,8 @@ public function add(Ticket $source, Ticket $target, $type = 'normal')
             ]
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
+        if ($response->hasError()) {
+            $this->setError($response->getError());
         }
 
         return $this;
@@ -110,11 +106,11 @@ public function remove(Ticket $source, Ticket $target, $type = 'normal')
     {
         $this->clearError();
 
-        if ( empty($source->getID()) || empty($target->getID()) ) {
+        if (empty($source->getID()) || empty($target->getID())) {
             $this->setError('Tickets not valid.');
             return $this;
         }
-        if ( !in_array($type, self::LINKTYPES, true) ) {
+        if (!in_array($type, self::LINKTYPES, true)) {
             $this->setError('Linktype is not supported.');
             return $this;
         }
@@ -131,8 +127,8 @@ public function remove(Ticket $source, Ticket $target, $type = 'normal')
             ]
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
+        if ($response->hasError()) {
+            $this->setError($response->getError());
             return $this;
         }
 
diff --git a/src/Resource/Organization.php b/src/Resource/Organization.php
index 4347c7f..f97992d 100644
--- a/src/Resource/Organization.php
+++ b/src/Resource/Organization.php
@@ -1,15 +1,12 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
 class Organization extends AbstractResource
 {
-    const URLS = [
+    public const URLS = [
         'get'    => 'organizations/{object_id}',
         'all'    => 'organizations',
         'create' => 'organizations',
@@ -37,12 +34,11 @@ public function import($csv_string)
             ]
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
-        }
-        else {
+        if ($response->hasError()) {
+            $this->setError($response->getError());
+        } else {
             $this->clearError();
-            $this->setRemoteData( $response->getData() );
+            $this->setRemoteData($response->getData());
         }
 
         return $this;
diff --git a/src/Resource/Tag.php b/src/Resource/Tag.php
index a9d640e..cfea140 100644
--- a/src/Resource/Tag.php
+++ b/src/Resource/Tag.php
@@ -1,15 +1,12 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Alexander Reichardt <alexander.reichardt@icloud.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
 class Tag extends AbstractResource
 {
-    const URLS = [
+    public const URLS = [
         'get'    => 'tags',
         'search' => 'tag_search?term={query}',
         'add'    => 'tags/add',
@@ -33,7 +30,7 @@ public function get($object_id, $object_type = 'Ticket')
         $this->clearError();
 
         $object_id = intval($object_id);
-        if ( empty($object_id) ) {
+        if (empty($object_id)) {
             throw new \RuntimeException('Missing object ID');
         }
 
@@ -45,12 +42,11 @@ public function get($object_id, $object_type = 'Ticket')
             ]
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
-        }
-        else {
+        if ($response->hasError()) {
+            $this->setError($response->getError());
+        } else {
             $this->clearError();
-            $this->setRemoteData( $response->getData() );
+            $this->setRemoteData($response->getData());
         }
 
         return $this;
@@ -70,11 +66,11 @@ public function add($object_id, $tag, $object_type = 'Ticket')
         $this->clearError();
 
         $object_id = intval($object_id);
-        if ( empty($object_id) ) {
+        if (empty($object_id)) {
             throw new \RuntimeException('Missing object ID');
         }
 
-        if ( empty($tag) ) {
+        if (empty($tag)) {
             throw new \RuntimeException('Missing tag');
         }
 
@@ -87,8 +83,8 @@ public function add($object_id, $tag, $object_type = 'Ticket')
             ]
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
+        if ($response->hasError()) {
+            $this->setError($response->getError());
         }
 
         return $this;
@@ -109,7 +105,7 @@ public function search($search_term, $page = null, $objects_per_page = null, $so
     {
         $this->clearError();
 
-        if ( empty($search_term) ) {
+        if (empty($search_term)) {
             throw new \RuntimeException('Missing search term');
         }
 
@@ -120,8 +116,8 @@ public function search($search_term, $page = null, $objects_per_page = null, $so
             ]
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
+        if ($response->hasError()) {
+            $this->setError($response->getError());
         }
 
         $this->clearError();
@@ -129,8 +125,8 @@ public function search($search_term, $page = null, $objects_per_page = null, $so
         // Return array of resource objects if no $object_id was given.
         // Note: the resource object (this object) used to execute get() will be left empty in this case.
         $objects = [];
-        foreach ( $response->getData() as $object_data ) {
-            $object = $this->getClient()->resource( get_class($this) );
+        foreach ($response->getData() as $object_data) {
+            $object = $this->getClient()->resource(get_class($this));
             $object->setRemoteData($object_data);
             $objects[] = $object;
         }
@@ -151,11 +147,11 @@ public function remove($object_id, $tag, $object_type = 'Ticket')
     {
         $this->clearError();
 
-        if ( empty($object_id) ) {
+        if (empty($object_id)) {
             throw new \RuntimeException('Missing object ID');
         }
 
-        if ( empty($tag) ) {
+        if (empty($tag)) {
             throw new \RuntimeException('Missing tag');
         }
 
@@ -169,8 +165,8 @@ public function remove($object_id, $tag, $object_type = 'Ticket')
             ]
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
+        if ($response->hasError()) {
+            $this->setError($response->getError());
             return $this;
         }
 
diff --git a/src/Resource/TextModule.php b/src/Resource/TextModule.php
index 7df5333..7c38048 100644
--- a/src/Resource/TextModule.php
+++ b/src/Resource/TextModule.php
@@ -1,15 +1,12 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
 class TextModule extends AbstractResource
 {
-    const URLS = [
+    public const URLS = [
         'get'    => 'text_modules/{object_id}',
         'all'    => 'text_modules',
         'create' => 'text_modules',
@@ -36,12 +33,11 @@ public function import($csv_string)
             ]
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
-        }
-        else {
+        if ($response->hasError()) {
+            $this->setError($response->getError());
+        } else {
             $this->clearError();
-            $this->setRemoteData( $response->getData() );
+            $this->setRemoteData($response->getData());
         }
 
         return $this;
diff --git a/src/Resource/Ticket.php b/src/Resource/Ticket.php
index fc532c9..67e5c73 100644
--- a/src/Resource/Ticket.php
+++ b/src/Resource/Ticket.php
@@ -1,9 +1,6 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
@@ -11,7 +8,7 @@
 
 class Ticket extends AbstractResource
 {
-    const URLS = [
+    public const URLS = [
         'get'    => 'tickets/{object_id}',
         'all'    => 'tickets',
         'create' => 'tickets',
@@ -23,19 +20,19 @@ class Ticket extends AbstractResource
     /**
      * Fetches TicketArticle objects of this Ticket object.
      *
-     * @return Array of TicketArticle objects   Returns array of ZammadAPIClient\Resource\TicketArticle objects or an empty array.
+     * @return array Array of TicketArticle objects.
      */
     public function getTicketArticles()
     {
         $this->clearError();
 
-        if ( empty( $this->getID() ) ) {
+        if (empty($this->getID())) {
             return [];
         }
 
-        $ticket_articles = $this->getClient()->resource( ResourceType::TICKET_ARTICLE )->getForTicket( $this->getID() );
-        if ( !is_array($ticket_articles) ) {
-            $this->setError( $ticket_articles->getError() );
+        $ticket_articles = $this->getClient()->resource(ResourceType::TICKET_ARTICLE)->getForTicket($this->getID());
+        if (!is_array($ticket_articles)) {
+            $this->setError($ticket_articles->getError());
             return [];
         }
 
diff --git a/src/Resource/TicketArticle.php b/src/Resource/TicketArticle.php
index f14b2f6..d503673 100644
--- a/src/Resource/TicketArticle.php
+++ b/src/Resource/TicketArticle.php
@@ -1,15 +1,12 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
 class TicketArticle extends AbstractResource
 {
-    const URLS = [
+    public const URLS = [
         'get'                    => 'ticket_articles/{object_id}',
         'get_for_ticket'         => 'ticket_articles/by_ticket/{ticket_id}',
         'get_attachment_content' => 'ticket_attachment/{ticket_id}/{ticket_article_id}/{object_id}',
@@ -27,14 +24,17 @@ class TicketArticle extends AbstractResource
      */
     public function getForTicket($ticket_id)
     {
-        if ( !empty( $this->getValues() ) ) {
-            throw new \RuntimeException('Object already contains values, getForTicket() not possible, use a new object');
+        if (!empty($this->getValues())) {
+            throw new \RuntimeException(
+                'Object already contains values, getForTicket() not possible, ' .
+                'use a new object'
+            );
         }
 
         $this->clearError();
 
         $ticket_id = intval($ticket_id);
-        if ( empty($ticket_id) ) {
+        if (empty($ticket_id)) {
             throw new \RuntimeException('Missing ticket ID');
         }
 
@@ -51,15 +51,15 @@ public function getForTicket($ticket_id)
             ]
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
+        if ($response->hasError()) {
+            $this->setError($response->getError());
             return $this;
         }
 
         // Return array of TicketArticle objects.
         $ticket_articles = [];
-        foreach ( $response->getData() as $ticket_article_data ) {
-            $ticket_article = $this->getClient()->resource( get_class($this) );
+        foreach ($response->getData() as $ticket_article_data) {
+            $ticket_article = $this->getClient()->resource(get_class($this));
             $ticket_article->setRemoteData($ticket_article_data);
             $ticket_articles[] = $ticket_article;
         }
@@ -82,20 +82,20 @@ public function getAttachmentContent($attachment_id)
             throw new \Exception('Attachment ID is invalid');
         }
 
-        if ( empty( $this->getID() ) ) {
+        if (empty($this->getID())) {
             throw new \Exception('Object data does not contain an ID, getAttachmentContent() not possible');
         }
 
         $this->clearError();
 
         $attachments = $this->getValue('attachments');
-        if ( !is_array($attachments) || !count($attachments) ) {
+        if (!is_array($attachments) || !count($attachments)) {
             return false;
         }
 
         // Check if given attachment ID exists for article.
-        $attachment_key = array_search( $attachment_id, array_column( $attachments, 'id' ) );
-        if ( $attachment_key === false ) {
+        $attachment_key = array_search($attachment_id, array_column($attachments, 'id'));
+        if ($attachment_key === false) {
             return false;
         }
         $attachment = $attachments[$attachment_key];
@@ -111,13 +111,13 @@ public function getAttachmentContent($attachment_id)
         );
 
         $response = $this->getClient()->get($url);
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
+        if ($response->hasError()) {
+            $this->setError($response->getError());
             return false;
         }
 
         $content = $response->getBody();
-        if ( $content instanceof \Psr\Http\Message\StreamInterface ) {
+        if ($content instanceof \Psr\Http\Message\StreamInterface) {
             $content = $content->getContents();
         }
         return $content;
diff --git a/src/Resource/TicketPriority.php b/src/Resource/TicketPriority.php
index 19a3843..f296866 100644
--- a/src/Resource/TicketPriority.php
+++ b/src/Resource/TicketPriority.php
@@ -1,15 +1,12 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
 class TicketPriority extends AbstractResource
 {
-    const URLS = [
+    public const URLS = [
         'get'    => 'ticket_priorities/{object_id}',
         'all'    => 'ticket_priorities',
         'create' => 'ticket_priorities',
diff --git a/src/Resource/TicketState.php b/src/Resource/TicketState.php
index 2a838f7..c34efb9 100644
--- a/src/Resource/TicketState.php
+++ b/src/Resource/TicketState.php
@@ -1,15 +1,12 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
 class TicketState extends AbstractResource
 {
-    const URLS = [
+    public const URLS = [
         'get'    => 'ticket_states/{object_id}',
         'all'    => 'ticket_states',
         'create' => 'ticket_states',
diff --git a/src/Resource/User.php b/src/Resource/User.php
index ad79224..f895741 100644
--- a/src/Resource/User.php
+++ b/src/Resource/User.php
@@ -1,15 +1,12 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
 class User extends AbstractResource
 {
-    const URLS = [
+    public const URLS = [
         'get'    => 'users/{object_id}',
         'all'    => 'users',
         'create' => 'users',
@@ -37,12 +34,11 @@ public function import($csv_string)
             ]
         );
 
-        if ( $response->hasError() ) {
-            $this->setError( $response->getError() );
-        }
-        else {
+        if ($response->hasError()) {
+            $this->setError($response->getError());
+        } else {
             $this->clearError();
-            $this->setRemoteData( $response->getData() );
+            $this->setRemoteData($response->getData());
         }
 
         return $this;
diff --git a/src/ResourceType.php b/src/ResourceType.php
index 4fe0f90..6435650 100644
--- a/src/ResourceType.php
+++ b/src/ResourceType.php
@@ -1,22 +1,19 @@
 <?php
 
-/**
- * @package Zammad API Client
- * @author  Jens Pfeifer <jens.pfeifer@znuny.com>
- */
+declare(strict_types=1);
 
 namespace ZammadAPIClient;
 
 class ResourceType
 {
-    const ORGANIZATION    = '\\ZammadAPIClient\\Resource\\Organization';
-    const GROUP           = '\\ZammadAPIClient\\Resource\\Group';
-    const USER            = '\\ZammadAPIClient\\Resource\\User';
-    const TEXT_MODULE     = '\\ZammadAPIClient\\Resource\\TextModule';
-    const TICKET_STATE    = '\\ZammadAPIClient\\Resource\\TicketState';
-    const TICKET_PRIORITY = '\\ZammadAPIClient\\Resource\\TicketPriority';
-    const TICKET          = '\\ZammadAPIClient\\Resource\\Ticket';
-    const TICKET_ARTICLE  = '\\ZammadAPIClient\\Resource\\TicketArticle';
-    const TAG             = '\\ZammadAPIClient\\Resource\\Tag';
-    const LINK            = '\\ZammadAPIClient\\Resource\\Link';
+    public const ORGANIZATION    = '\\ZammadAPIClient\\Resource\\Organization';
+    public const GROUP           = '\\ZammadAPIClient\\Resource\\Group';
+    public const USER            = '\\ZammadAPIClient\\Resource\\User';
+    public const TEXT_MODULE     = '\\ZammadAPIClient\\Resource\\TextModule';
+    public const TICKET_STATE    = '\\ZammadAPIClient\\Resource\\TicketState';
+    public const TICKET_PRIORITY = '\\ZammadAPIClient\\Resource\\TicketPriority';
+    public const TICKET          = '\\ZammadAPIClient\\Resource\\Ticket';
+    public const TICKET_ARTICLE  = '\\ZammadAPIClient\\Resource\\TicketArticle';
+    public const TAG             = '\\ZammadAPIClient\\Resource\\Tag';
+    public const LINK            = '\\ZammadAPIClient\\Resource\\Link';
 }
diff --git a/test/ZammadAPIClient/Client/ResponseTest.php b/test/ZammadAPIClient/Client/ResponseTest.php
index 0e6e11a..06885cf 100644
--- a/test/ZammadAPIClient/Client/ResponseTest.php
+++ b/test/ZammadAPIClient/Client/ResponseTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Client;
 
diff --git a/test/ZammadAPIClient/ClientTest.php b/test/ZammadAPIClient/ClientTest.php
index 01db0cb..4920d40 100644
--- a/test/ZammadAPIClient/ClientTest.php
+++ b/test/ZammadAPIClient/ClientTest.php
@@ -1,7 +1,9 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient;
 
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
 use ZammadAPIClient\Client;
@@ -55,6 +57,7 @@ public function testRemovesFromHeaderAfterUnsetOnBehalfOfUser()
         $this->assertArrayNotHasKey('From', $this->capturedOptions['headers']);
     }
 
+    #[Group('integration')]
     public function testFromHeaderAgainstZammad()
     {
         $client = self::createZammadClient();
@@ -87,6 +90,10 @@ private function createClientWithMockHttpClient()
         $this->capturedOptions = [];
 
         $mockResponse = $this->createMock(ResponseInterface::class);
+        $mockResponse->method('getStatusCode')->willReturn(200);
+        $mockResponse->method('getReasonPhrase')->willReturn('OK');
+        $mockResponse->method('getBody')->willReturn('{}');
+        $mockResponse->method('getHeaders')->willReturn([]);
 
         $mockHttpClient = $this->createMock(HTTPClientInterface::class);
         $mockHttpClient
diff --git a/test/ZammadAPIClient/EnvConfigTrait.php b/test/ZammadAPIClient/EnvConfigTrait.php
index 08ea826..99f7eeb 100644
--- a/test/ZammadAPIClient/EnvConfigTrait.php
+++ b/test/ZammadAPIClient/EnvConfigTrait.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient;
 
diff --git a/test/ZammadAPIClient/GetIDTest.php b/test/ZammadAPIClient/GetIDTest.php
index 75db368..b8bd304 100644
--- a/test/ZammadAPIClient/GetIDTest.php
+++ b/test/ZammadAPIClient/GetIDTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient;
 
diff --git a/test/ZammadAPIClient/Resource/AbstractBaseTest.php b/test/ZammadAPIClient/Resource/AbstractBaseTest.php
index 690d46f..8d84025 100644
--- a/test/ZammadAPIClient/Resource/AbstractBaseTest.php
+++ b/test/ZammadAPIClient/Resource/AbstractBaseTest.php
@@ -1,14 +1,17 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
 use ZammadAPIClient\Client;
 use ZammadAPIClient\EnvConfigTrait;
 use ZammadAPIClient\Exception\AlreadyFetchedObjectException;
 
-abstract class AbstractBaseTest extends TestCase
+abstract #[Group('integration')]
+class AbstractBaseTest extends TestCase
 {
     use EnvConfigTrait;
 
diff --git a/test/ZammadAPIClient/Resource/GroupTest.php b/test/ZammadAPIClient/Resource/GroupTest.php
index bb73696..f76e860 100644
--- a/test/ZammadAPIClient/Resource/GroupTest.php
+++ b/test/ZammadAPIClient/Resource/GroupTest.php
@@ -1,9 +1,12 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
+use PHPUnit\Framework\Attributes\Group;
 use ZammadAPIClient\ResourceType;
 
+#[Group('integration')]
 class GroupTest extends AbstractBaseTest
 {
     protected $resource_type = ResourceType::GROUP;
diff --git a/test/ZammadAPIClient/Resource/LinkTest.php b/test/ZammadAPIClient/Resource/LinkTest.php
index 3317969..7284dd9 100644
--- a/test/ZammadAPIClient/Resource/LinkTest.php
+++ b/test/ZammadAPIClient/Resource/LinkTest.php
@@ -1,11 +1,14 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 use ZammadAPIClient\Client;
 use ZammadAPIClient\ResourceType;
 
+#[Group('integration')]
 class LinkTest extends TestCase
 {
     private static $client;
diff --git a/test/ZammadAPIClient/Resource/OrganizationTest.php b/test/ZammadAPIClient/Resource/OrganizationTest.php
index f7cb057..9339328 100644
--- a/test/ZammadAPIClient/Resource/OrganizationTest.php
+++ b/test/ZammadAPIClient/Resource/OrganizationTest.php
@@ -1,9 +1,12 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
+use PHPUnit\Framework\Attributes\Group;
 use ZammadAPIClient\ResourceType;
 
+#[Group('integration')]
 class OrganizationTest extends AbstractBaseTest
 {
     protected $resource_type = ResourceType::ORGANIZATION;
diff --git a/test/ZammadAPIClient/Resource/TagTest.php b/test/ZammadAPIClient/Resource/TagTest.php
index 2fa9dc6..1823755 100644
--- a/test/ZammadAPIClient/Resource/TagTest.php
+++ b/test/ZammadAPIClient/Resource/TagTest.php
@@ -1,11 +1,14 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 use ZammadAPIClient\Client;
 use ZammadAPIClient\ResourceType;
 
+#[Group('integration')]
 class TagTest extends TestCase
 {
     private static $client;
diff --git a/test/ZammadAPIClient/Resource/TextModuleTest.php b/test/ZammadAPIClient/Resource/TextModuleTest.php
index c90eadf..ba42a02 100644
--- a/test/ZammadAPIClient/Resource/TextModuleTest.php
+++ b/test/ZammadAPIClient/Resource/TextModuleTest.php
@@ -1,9 +1,12 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
+use PHPUnit\Framework\Attributes\Group;
 use ZammadAPIClient\ResourceType;
 
+#[Group('integration')]
 class TextModuleTest extends AbstractBaseTest
 {
     protected $resource_type = ResourceType::TEXT_MODULE;
diff --git a/test/ZammadAPIClient/Resource/TicketArticleTest.php b/test/ZammadAPIClient/Resource/TicketArticleTest.php
index 7eb4e3f..c4fc5e4 100644
--- a/test/ZammadAPIClient/Resource/TicketArticleTest.php
+++ b/test/ZammadAPIClient/Resource/TicketArticleTest.php
@@ -1,9 +1,12 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
+use PHPUnit\Framework\Attributes\Group;
 use ZammadAPIClient\ResourceType;
 
+#[Group('integration')]
 class TicketArticleTest extends AbstractBaseTest
 {
     protected $resource_type = ResourceType::TICKET_ARTICLE;
diff --git a/test/ZammadAPIClient/Resource/TicketPriorityTest.php b/test/ZammadAPIClient/Resource/TicketPriorityTest.php
index 95ee9a4..e853986 100644
--- a/test/ZammadAPIClient/Resource/TicketPriorityTest.php
+++ b/test/ZammadAPIClient/Resource/TicketPriorityTest.php
@@ -1,9 +1,12 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
+use PHPUnit\Framework\Attributes\Group;
 use ZammadAPIClient\ResourceType;
 
+#[Group('integration')]
 class TicketPriorityTest extends AbstractBaseTest
 {
     protected $resource_type = ResourceType::TICKET_PRIORITY;
diff --git a/test/ZammadAPIClient/Resource/TicketStateTest.php b/test/ZammadAPIClient/Resource/TicketStateTest.php
index e983bfa..b072f3a 100644
--- a/test/ZammadAPIClient/Resource/TicketStateTest.php
+++ b/test/ZammadAPIClient/Resource/TicketStateTest.php
@@ -1,9 +1,12 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
+use PHPUnit\Framework\Attributes\Group;
 use ZammadAPIClient\ResourceType;
 
+#[Group('integration')]
 class TicketStateTest extends AbstractBaseTest
 {
     protected $resource_type = ResourceType::TICKET_STATE;
diff --git a/test/ZammadAPIClient/Resource/TicketTest.php b/test/ZammadAPIClient/Resource/TicketTest.php
index 4523d98..b089ac3 100644
--- a/test/ZammadAPIClient/Resource/TicketTest.php
+++ b/test/ZammadAPIClient/Resource/TicketTest.php
@@ -1,10 +1,13 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
+use PHPUnit\Framework\Attributes\Group;
 use ZammadAPIClient\Exception\AlreadyFetchedObjectException;
 use ZammadAPIClient\ResourceType;
 
+#[Group('integration')]
 class TicketTest extends AbstractBaseTest
 {
     protected $resource_type = ResourceType::TICKET;
diff --git a/test/ZammadAPIClient/Resource/UserTest.php b/test/ZammadAPIClient/Resource/UserTest.php
index 21f2c39..e70c02a 100644
--- a/test/ZammadAPIClient/Resource/UserTest.php
+++ b/test/ZammadAPIClient/Resource/UserTest.php
@@ -1,9 +1,12 @@
 <?php
+declare(strict_types=1);
 
 namespace ZammadAPIClient\Resource;
 
+use PHPUnit\Framework\Attributes\Group;
 use ZammadAPIClient\ResourceType;
 
+#[Group('integration')]
 class UserTest extends AbstractBaseTest
 {
     protected $resource_type = ResourceType::USER;
diff --git a/test/bootstrap.php b/test/bootstrap.php
index 3751a60..0873075 100644
--- a/test/bootstrap.php
+++ b/test/bootstrap.php
@@ -1,22 +1,58 @@
 <?php
+declare(strict_types=1);
 
-function IncludeIfExists($File)
-{
-    if ( file_exists($File) ) {
-        return include $File;
+$composerAutoloadFiles = [
+    __DIR__ . '/../vendor/autoload.php',
+    __DIR__ . '/../../../autoload.php',
+    __DIR__ . '/../../../.composer/autoload.php',
+];
+
+foreach ($composerAutoloadFiles as $autoloadFile) {
+    if (!is_file($autoloadFile)) {
+        continue;
     }
+
+    $loader = require $autoloadFile;
+    $loader->add('ZammadAPIClient', __DIR__);
+
+    return $loader;
 }
 
-if (
-    ( !$Loader = IncludeIfExists( __DIR__.'/../vendor/autoload.php' ) )
-    && ( !$Loader = IncludeIfExists( __DIR__.'/../../../.composer/autoload.php' ) )
-) {
-    die(
-        'You must set up the project dependencies, run the following commands:' . PHP_EOL
-        . 'curl -s http://getcomposer.org/installer | php' . PHP_EOL
-        . 'php composer.phar install' . PHP_EOL
-    );
+$systemAutoloadFiles = [
+    '/usr/share/php/GuzzleHttp/autoload.php',
+    '/usr/share/php/Mockery/autoload.php',
+    '/usr/share/php/Psr/Http/Client/autoload.php',
+    '/usr/share/php/Psr/Http/Message/autoload.php',
+    '/usr/share/php/Psr/Log/autoload.php',
+];
+
+foreach ($systemAutoloadFiles as $autoloadFile) {
+    if (is_file($autoloadFile)) {
+        require_once $autoloadFile;
+    }
 }
 
-$Loader->add( 'ZammadAPIClient', __DIR__ );
-return $Loader;
+spl_autoload_register(static function (string $class): void {
+    if (!str_starts_with($class, 'ZammadAPIClient\\')) {
+        return;
+    }
+
+    $relativeClass = str_replace('\\', '/', substr($class, strlen('ZammadAPIClient\\')));
+    $relativePath = $relativeClass . '.php';
+    $candidateFiles = [
+        __DIR__ . '/../src/' . $relativePath,
+        __DIR__ . '/ZammadAPIClient/' . $relativePath,
+    ];
+
+    foreach ($candidateFiles as $candidateFile) {
+        if (!is_file($candidateFile)) {
+            continue;
+        }
+
+        require_once $candidateFile;
+
+        return;
+    }
+});
+
+return true;

From c200c38f25ee76458effd59f0a9c597e033f10b6 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 11 Jun 2026 12:01:56 +0000
Subject: [PATCH 3/4] Address validation feedback

---
 .github/workflows/tests.yml | 3 +++
 test/bootstrap.php          | 4 ++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index a4f347d..2742bfd 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -6,6 +6,9 @@ on:
   pull_request:
   workflow_dispatch:
 
+permissions:
+  contents: read
+
 jobs:
   unit:
     if: github.event_name != 'workflow_dispatch'
diff --git a/test/bootstrap.php b/test/bootstrap.php
index 0873075..3a1b31d 100644
--- a/test/bootstrap.php
+++ b/test/bootstrap.php
@@ -15,7 +15,7 @@
     $loader = require $autoloadFile;
     $loader->add('ZammadAPIClient', __DIR__);
 
-    return $loader;
+    return;
 }
 
 $systemAutoloadFiles = [
@@ -55,4 +55,4 @@
     }
 });
 
-return true;
+return;

From 99dc32039e1d9a165aa03d796e628ece35fc0d50 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 11 Jun 2026 12:02:58 +0000
Subject: [PATCH 4/4] Refine validation follow-ups

---
 test/bootstrap.php | 1 -
 1 file changed, 1 deletion(-)

diff --git a/test/bootstrap.php b/test/bootstrap.php
index 3a1b31d..cea0cf1 100644
--- a/test/bootstrap.php
+++ b/test/bootstrap.php
@@ -4,7 +4,6 @@
 $composerAutoloadFiles = [
     __DIR__ . '/../vendor/autoload.php',
     __DIR__ . '/../../../autoload.php',
-    __DIR__ . '/../../../.composer/autoload.php',
 ];
 
 foreach ($composerAutoloadFiles as $autoloadFile) {