diff --git a/.editorconfig b/.editorconfig
deleted file mode 100644
index a7c44dd..0000000
--- a/.editorconfig
+++ /dev/null
@@ -1,15 +0,0 @@
-root = true
-
-[*]
-charset = utf-8
-indent_size = 4
-indent_style = space
-end_of_line = lf
-insert_final_newline = true
-trim_trailing_whitespace = true
-
-[*.md]
-trim_trailing_whitespace = false
-
-[*.{yml,yaml}]
-indent_size = 2
diff --git a/.github/workflows/dependabot-auto-merge.yml b/.github/workflows/dependabot-auto-merge.yml
deleted file mode 100644
index b4979d6..0000000
--- a/.github/workflows/dependabot-auto-merge.yml
+++ /dev/null
@@ -1,33 +0,0 @@
-name: dependabot-auto-merge
-on: pull_request_target
-
-permissions:
-  pull-requests: write
-  contents: write
-
-jobs:
-  dependabot:
-    runs-on: ubuntu-latest
-    timeout-minutes: 5
-    if: ${{ github.actor == 'dependabot[bot]' }}
-    steps:
-
-      - name: Dependabot metadata
-        id: metadata
-        uses: dependabot/fetch-metadata@v2.3.0
-        with:
-          github-token: "${{ secrets.GITHUB_TOKEN }}"
-
-      - name: Auto-merge Dependabot PRs for semver-minor updates
-        if: ${{steps.metadata.outputs.update-type == 'version-update:semver-minor'}}
-        run: gh pr merge --auto --merge "$PR_URL"
-        env:
-          PR_URL: ${{github.event.pull_request.html_url}}
-          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
-
-      - name: Auto-merge Dependabot PRs for semver-patch updates
-        if: ${{steps.metadata.outputs.update-type == 'version-update:semver-patch'}}
-        run: gh pr merge --auto --merge "$PR_URL"
-        env:
-          PR_URL: ${{github.event.pull_request.html_url}}
-          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
diff --git a/.gitignore b/.gitignore
index dc8d529..38a0e27 100644
--- a/.gitignore
+++ b/.gitignore
@@ -18,6 +18,7 @@ yarn-error.log
 /.idea
 /.fleet
 /.vscode
+.editorconfig
 
 # Code sniffer
 .php_cs
diff --git a/rector.php b/rector.php
index ead3c6f..c1cbd7b 100644
--- a/rector.php
+++ b/rector.php
@@ -9,8 +9,4 @@
         __DIR__.'/src',
         __DIR__.'/tests',
     ])
-    // uncomment to reach your current PHP version
-    // ->withPhpSets()
-    ->withTypeCoverageLevel(0)
-    ->withDeadCodeLevel(0)
-    ->withCodeQualityLevel(0);
+    ->withPhpSets();
diff --git a/src/Client/HttpClientService.php b/src/Client/HttpClientService.php
index 45e7798..f1221a1 100644
--- a/src/Client/HttpClientService.php
+++ b/src/Client/HttpClientService.php
@@ -26,17 +26,14 @@ class HttpClientService
 
     private bool $verifySsl = false;
 
-    private bool $test_mode;
-
-    private HttpClientInterface $httpClient;
+    private readonly HttpClientInterface $httpClient;
 
     /**
      * @param  bool  $test_mode  Whether to use the test API or not.
      * @param  HttpClientInterface|null  $httpClient  Injected HTTP client for testing (optional).
      */
-    public function __construct(bool $test_mode = false, ?HttpClientInterface $httpClient = null)
+    public function __construct(private readonly bool $test_mode = false, ?HttpClientInterface $httpClient = null)
     {
-        $this->test_mode = $test_mode;
         $this->httpClient = $httpClient ?? new RetryableHttpClient(HttpClient::create($this->getClientOptions()), null, $this->maxRetries);
     }
 
diff --git a/src/SatimConfig.php b/src/SatimConfig.php
index 318177c..ca45818 100644
--- a/src/SatimConfig.php
+++ b/src/SatimConfig.php
@@ -64,7 +64,7 @@ abstract class SatimConfig
      *
      * @var non-empty-string|null
      */
-    protected ?string $failUrl;
+    protected ?string $failUrl = null;
 
     /**
      * The URL to redirect to after the payment is processed.
diff --git a/src/SatimStatusChecker.php b/src/SatimStatusChecker.php
index b48c869..4a1d79b 100644
--- a/src/SatimStatusChecker.php
+++ b/src/SatimStatusChecker.php
@@ -64,7 +64,7 @@ public function isRejected(): bool
             return false;
         }
 
-        if (! empty($response['ErrorMessage']) && str_contains($response['ErrorMessage'], 'Payment is declined')) {
+        if (! empty($response['ErrorMessage']) && str_contains((string) $response['ErrorMessage'], 'Payment is declined')) {
             return true;
         }
 
@@ -154,7 +154,7 @@ public function isCancelled(): bool
             return false;
         }
 
-        if (! empty($this->getResponse()['ErrorMessage']) && str_contains($this->getResponse()['ErrorMessage'], 'Payment is cancelled')) {
+        if (! empty($this->getResponse()['ErrorMessage']) && str_contains((string) $this->getResponse()['ErrorMessage'], 'Payment is cancelled')) {
             return true;
         }
 
diff --git a/tests/Unit/SatimTest.php b/tests/Unit/SatimTest.php
index 06b4fa6..4f46ced 100644
--- a/tests/Unit/SatimTest.php
+++ b/tests/Unit/SatimTest.php
@@ -130,7 +130,7 @@
     $requestData = $method->invoke($this->satim);
 
     // Decode JSON `jsonParams`
-    $jsonParams = json_decode($requestData['jsonParams'], true);
+    $jsonParams = json_decode((string) $requestData['jsonParams'], true);
 
     expect($jsonParams)->toHaveKeys(['force_terminal_id', 'custom_field_1', 'custom_field_2'])
         ->and($jsonParams['force_terminal_id'])->toBe('123456')
@@ -157,7 +157,7 @@
     $requestData = $method->invoke($this->satim);
 
     // Decode JSON `jsonParams`
-    $jsonParams = json_decode($requestData['jsonParams'], true);
+    $jsonParams = json_decode((string) $requestData['jsonParams'], true);
 
     expect($jsonParams)->toHaveKey('force_terminal_id')
         ->and($jsonParams)->not()->toHaveKeys(['custom_field_1', 'custom_field_2']);
@@ -185,7 +185,7 @@
     $requestData = $method->invoke($this->satim);
 
     // Decode JSON `jsonParams`
-    $jsonParams = json_decode($requestData['jsonParams'], true);
+    $jsonParams = json_decode((string) $requestData['jsonParams'], true);
 
     expect($jsonParams)->toHaveKey('force_terminal_id')
         ->and($jsonParams['force_terminal_id'])->toBe('OVERWRITTEN_VALUE')