diff --git a/composer.json b/composer.json
index 62ee260..30a4125 100644
--- a/composer.json
+++ b/composer.json
@@ -23,8 +23,7 @@
     "simplesamlphp/simplesamlphp-test-framework": "^1.7",
     "phpunit/phpunit": "^10",
     "psalm/plugin-phpunit": "^0.19.0",
-    "squizlabs/php_codesniffer": "^3.7",
-    "dg/bypass-finals": "^1.8"
+    "squizlabs/php_codesniffer": "^3.7"
   },
   "autoload": {
     "psr-4": {
@@ -49,7 +48,7 @@
   },
   "scripts": {
     "validate": [
-      "vendor/bin/phpunit --no-coverage",
+      "vendor/bin/phpunit --no-coverage --testdox",
       "vendor/bin/phpcs -p",
       "vendor/bin/psalm --no-cache"
     ],
diff --git a/docs/APPLE.md b/docs/APPLE.md
index 7246c80..2a5533a 100644
--- a/docs/APPLE.md
+++ b/docs/APPLE.md
@@ -77,4 +77,8 @@ docker run --name ssp-apple-oidc \
 
 Edit your `/etc/hosts` file to make `apple.test.idpproxy.illinois.edu` route to local host and then visit
  `https://apple.test.idpproxy.illinois.edu/simplesaml/module.php/core/authenticate.php?as=appleTest` to
-initiate a login to Apple. Non-secret values such as keyId and teamId
\ No newline at end of file
+initiate a login to Apple. Non-secret values such as keyId and teamId
+
+# Documentation
+
+* [TN3107: Resolving Sign in with Apple response errors](https://developer.apple.com/documentation/technotes/tn3107-resolving-sign-in-with-apple-response-errors)
\ No newline at end of file
diff --git a/phpunit.xml b/phpunit.xml
index 0a8f4ea..c60752c 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -8,10 +8,6 @@
          displayDetailsOnTestsThatTriggerDeprecations="true"
          backupGlobals="false"
 >
-    <extensions>
-        <bootstrap class="DG\BypassFinals\PHPUnitExtension"/>
-    </extensions>
-
     <testsuites>
         <testsuite name="The project's test suite">
             <directory>./tests</directory>
diff --git a/src/Controller/OIDCLogoutController.php b/src/Controller/OIDCLogoutController.php
index 9c731cf..22b1f5d 100644
--- a/src/Controller/OIDCLogoutController.php
+++ b/src/Controller/OIDCLogoutController.php
@@ -12,6 +12,8 @@
 use SimpleSAML\Logger;
 use SimpleSAML\Module\authoauth2\Auth\Source\OAuth2;
 use SimpleSAML\Module\authoauth2\Auth\Source\OpenIDConnect;
+use SimpleSAML\Module\authoauth2\Codebooks\LegacyRoutesEnum;
+use SimpleSAML\Module\authoauth2\Codebooks\RoutesEnum;
 use SimpleSAML\Module\authoauth2\Controller\Traits\RequestTrait;
 use SimpleSAML\Module\authoauth2\locators\SourceServiceLocator;
 use Symfony\Component\HttpFoundation\Request;
@@ -55,9 +57,8 @@ public function __construct(Configuration $config = null)
      */
     public function loggedout(Request $request): void
     {
-        Logger::debug('authoauth2: logout request=' . var_export($request->request->all(), true));
-
         $this->parseRequest($request);
+        Logger::debug('authoauth2: logout request=' . var_export($this->requestParams, true));
 
         \assert(\is_array($this->state));
 
@@ -72,19 +73,22 @@ public function loggedout(Request $request): void
      */
     public function logout(Request $request): void
     {
-        Logger::debug('authoauth2: logout request=' . var_export($request->request->all(), true));
+        $this->parseRequestParamsSingleton($request);
+        Logger::debug('authoauth2: logout request=' . var_export($this->requestParams, true));
         // Find the authentication source
-        if (!$request->query->has('authSource')) {
+        if (!isset($this->requestParams['authSource'])) {
             throw new BadRequest('No authsource in the request');
         }
-        $sourceId = $request->query->get('authSource');
+        $sourceId = $this->requestParams['authSource'];
         if (empty($sourceId) || !\is_string($sourceId)) {
             throw new BadRequest('Authsource ID invalid');
         }
+        $logoutRoute = $this->config->getOptionalBoolean('useLegacyRoutes', false) ?
+            LegacyRoutesEnum::LegacyLogout->value : RoutesEnum::Logout->value;
         $this->getAuthSource($sourceId)
             ->logout([
                          'oidc:localLogout' => true,
-                         'ReturnTo' => $this->config->getBasePath() . 'logout.php',
+                         'ReturnTo' => $this->config->getBasePath() . $logoutRoute,
                      ]);
     }
 
diff --git a/src/Controller/Oauth2Controller.php b/src/Controller/Oauth2Controller.php
index 359c0df..701d948 100644
--- a/src/Controller/Oauth2Controller.php
+++ b/src/Controller/Oauth2Controller.php
@@ -51,9 +51,8 @@ public function __construct()
      */
     public function linkback(Request $request): void
     {
-        Logger::debug('authoauth2: linkback request=' . var_export($request->query->all(), true));
-
         $this->parseRequest($request);
+        Logger::debug('authoauth2: linkback request=' . var_export($this->requestParams, true));
 
         // Required for psalm
         \assert($this->source instanceof  OAuth2);
@@ -61,12 +60,14 @@ public function linkback(Request $request): void
         \assert(\is_string($this->sourceId));
 
         // Handle Identify Provider error
-        if (!$request->query->has('code') || empty($request->query->get('code'))) {
+        if (empty($this->requestParams['code'])) {
             $this->handleError($this->source, $this->state, $request);
+            // Used to facilitate testing
+            return;
         }
 
         try {
-            $this->source->finalStep($this->state, (string)$request->query->get('code'));
+            $this->source->finalStep($this->state, (string)$this->requestParams['code']);
         } catch (IdentityProviderException $e) {
             // phpcs:ignore Generic.Files.LineLength.TooLong
             Logger::error("authoauth2: error in '$this->sourceId' msg '{$e->getMessage()}' body '" . var_export($e->getResponseBody(), true) . "'");
diff --git a/src/Controller/Traits/ErrorTrait.php b/src/Controller/Traits/ErrorTrait.php
index 53b4bb5..c47806a 100644
--- a/src/Controller/Traits/ErrorTrait.php
+++ b/src/Controller/Traits/ErrorTrait.php
@@ -5,6 +5,7 @@
 namespace SimpleSAML\Module\authoauth2\Controller\Traits;
 
 use Symfony\Component\HttpFoundation\Request;
+use SimpleSAML\Module\authoauth2\Lib\RequestUtilities;
 
 trait ErrorTrait
 {
@@ -15,16 +16,17 @@ trait ErrorTrait
      */
     public function parseError(Request $request): array
     {
+        $requestParams = RequestUtilities::getRequestParams($request);
         // Do not throw if errors are suppressed by @ operator
         // error_reporting() value for suppressed errors changed in PHP 8.0.0
         $error = '';
         $error_description = '';
-        if ($request->query->has('error')) {
-            $error = (string)$request->query->get('error');
+        if (isset($requestParams['error'])) {
+            $error = (string)$requestParams['error'];
         }
 
-        if ($request->query->has('error_description')) {
-            $error_description = (string)$request->query->get('error_description');
+        if (isset($requestParams['error_description'])) {
+            $error_description = (string)$requestParams['error_description'];
         }
 
         return [
diff --git a/src/Controller/Traits/RequestTrait.php b/src/Controller/Traits/RequestTrait.php
index 3ca5df6..2fd5711 100644
--- a/src/Controller/Traits/RequestTrait.php
+++ b/src/Controller/Traits/RequestTrait.php
@@ -9,8 +9,9 @@
 use SimpleSAML\Error\BadRequest;
 use SimpleSAML\Error\NoState;
 use SimpleSAML\Module\authoauth2\Auth\Source\OAuth2;
-use SimpleSAML\Module\authoauth2\Codebooks\RoutesEnum;
 use SimpleSAML\Module\authoauth2\Codebooks\LegacyRoutesEnum;
+use SimpleSAML\Module\authoauth2\Codebooks\RoutesEnum;
+use SimpleSAML\Module\authoauth2\Lib\RequestUtilities;
 use SimpleSAML\Module\authoauth2\locators\SourceServiceLocator;
 use Symfony\Component\HttpFoundation\Request;
 
@@ -36,6 +37,9 @@ trait RequestTrait
      */
     protected string $expectedStateAuthId = OAuth2::AUTHID;
 
+    /** @var array  */
+    protected array $requestParams = [];
+
     /**
      * @param   Request  $request
      *
@@ -43,11 +47,13 @@ trait RequestTrait
      */
     public function stateIsValid(Request $request): bool
     {
-        if (!$request->query->has('state')) {
+        // Parse the request parameters
+        $this->parseRequestParamsSingleton($request);
+        if (!isset($this->requestParams['state'])) {
             return false;
         }
         /** @var ?string $stateId */
-        $stateId = $request->query->get('state');
+        $stateId = $this->requestParams['state'];
         if (empty($stateId)) {
             return false;
         }
@@ -72,7 +78,7 @@ public function parseRequest(Request $request): void
             };
             throw new BadRequest($message);
         }
-        $stateIdWithPrefix = (string)($request->query->get('state') ?? '');
+        $stateIdWithPrefix = (string)($this->requestParams['state'] ?? '');
         $stateId = substr($stateIdWithPrefix, \strlen($this->expectedPrefix));
 
         $this->state = $this->loadState($stateId, $this->expectedStageState);
@@ -110,4 +116,14 @@ public function loadState(string $id, string $stage, bool $allowMissing = false)
     {
         return State::loadState($id, $stage, $allowMissing);
     }
+
+    /**
+     * @param   Request  $request
+     */
+    public function parseRequestParamsSingleton(Request $request): void
+    {
+        if (empty($this->requestParams)) {
+            $this->requestParams = RequestUtilities::getRequestParams($request);
+        }
+    }
 }
diff --git a/src/Lib/RequestUtilities.php b/src/Lib/RequestUtilities.php
new file mode 100644
index 0000000..66bf56f
--- /dev/null
+++ b/src/Lib/RequestUtilities.php
@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\Module\authoauth2\Lib;
+
+use Symfony\Component\HttpFoundation\Request;
+
+class RequestUtilities
+{
+    /**
+     * @param   Request  $request
+     *
+     * @return array
+     */
+    public static function getRequestParams(Request $request): array
+    {
+        $params = [];
+        if ($request->isMethod('GET')) {
+            $params = $request->query->all();
+        } elseif ($request->isMethod('POST')) {
+            $params = $request->request->all();
+        }
+
+        return $params;
+    }
+}
diff --git a/tests/lib/Controller/OIDCLogoutControllerTest.php b/tests/lib/Controller/OIDCLogoutControllerTest.php
index f8a90a7..e983549 100644
--- a/tests/lib/Controller/OIDCLogoutControllerTest.php
+++ b/tests/lib/Controller/OIDCLogoutControllerTest.php
@@ -5,17 +5,17 @@
 namespace SimpleSAML\Module\authoauth2\Tests\Controller;
 
 use DG\BypassFinals;
+use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\MockObject\Exception;
 use PHPUnit\Framework\TestCase;
-use SimpleSAML\Auth\Source;
-use SimpleSAML\Configuration;
+use SimpleSAML\Auth\Simple;
 use SimpleSAML\Error\BadRequest;
 use SimpleSAML\Module\authoauth2\Auth\Source\OAuth2;
 use SimpleSAML\Module\authoauth2\Auth\Source\OpenIDConnect;
+use SimpleSAML\Module\authoauth2\Codebooks\RoutesEnum;
 use SimpleSAML\Module\authoauth2\Controller\OIDCLogoutController;
 use SimpleSAML\Module\authoauth2\Controller\Traits\RequestTrait;
 use SimpleSAML\Module\authoauth2\locators\SourceService;
-use Symfony\Component\HttpFoundation\InputBag;
 use Symfony\Component\HttpFoundation\Request;
 
 // Unless we declare the class here, it is not recognized by phpcs
@@ -23,21 +23,6 @@ class OIDCLogoutControllerMock extends OIDCLogoutController
 {
     use RequestTrait;
 
-    public function setSource(Source $source): void
-    {
-        $this->source = $source;
-    }
-
-    public function setState(array $state): void
-    {
-        $this->state = $state;
-    }
-
-    public function setSourceId(string $sourceId): void
-    {
-        $this->sourceId = $sourceId;
-    }
-
     public function getExpectedStageState(): string
     {
         return $this->expectedStageState;
@@ -54,37 +39,25 @@ class OIDCLogoutControllerTest extends TestCase
 {
     /** @var OIDCLogoutControllerMock */
     private $controller;
-    /** @var Request */
-    private $requestMock;
-    /** @var Configuration */
-    private $configMock;
-    private array $stateMock;
     /** @var SourceService */
     private $sourceServiceMock;
+    /** @var \PHPUnit\Framework\MockObject\MockObject|(OAuth2&\PHPUnit\Framework\MockObject\MockObject) */
+    private $oauth2Mock;
+    /** @var \PHPUnit\Framework\MockObject\MockObject|(Simple&\PHPUnit\Framework\MockObject\MockObject) */
+    private $simpleMock;
+    private array $stateMock;
+    private array $parametersMock;
 
     /**
      * @throws Exception
      */
     protected function setUp(): void
     {
-        BypassFinals::enable(bypassReadOnly: false);
-
-        $this->configMock = $this->createMock(Configuration::class);
+        $this->parametersMock = ['state' => OAuth2::STATE_PREFIX . '-statefoo'];
+        $this->stateMock = [OAuth2::AUTHID => 'testSourceId'];
 
-        // Initial state setup
-        $this->stateMock = ['state' => 'testState'];
-
-        $this->controller = $this->getMockBuilder(OIDCLogoutControllerMock::class)
-            ->setConstructorArgs([$this->configMock])
-            ->onlyMethods(['parseRequest', 'getSourceService', 'getAuthSource'])
-            ->getMock();
-
-        $this->requestMock = $this->getMockBuilder(Request::class)->getMock();
-
-        $this->controller->method('getSourceService')
-            ->willReturn($this->createMock(SourceService::class));
-
-        $this->sourceServiceMock = $this->controller->getSourceService();
+        // Create the mock controller
+        $this->createControllerMock(['getSourceService', 'loadState', 'getAuthSource']);
     }
 
     public function testExpectedConstVariables(): void
@@ -93,11 +66,26 @@ public function testExpectedConstVariables(): void
         $this->assertEquals(OAuth2::STATE_PREFIX . '-', $this->controller->getExpectedPrefix());
     }
 
-    public function testLoggedOutSuccess(): void
+    public static function requestMethod(): array
     {
-        $this->controller->setState($this->stateMock);
+        return [
+            'GET' => ['GET'],
+            'POST' => ['POST'],
+        ];
+    }
 
-        $this->requestMock->request = $this->createRequestMock([]);
+    #[DataProvider('requestMethod')]
+    public function testLoggedOutSuccess(string $requestMethod): void
+    {
+        $parameters = [
+            ...$this->parametersMock,
+        ];
+
+        $request = Request::create(
+            uri: 'https://localhost/auth/authorize',
+            method: $requestMethod,
+            parameters: $parameters,
+        );
 
         /** @psalm-suppress UndefinedMethod,MixedMethodCall */
         $this->sourceServiceMock
@@ -105,68 +93,112 @@ public function testLoggedOutSuccess(): void
             ->method('completeLogout')
             ->with($this->stateMock);
 
-        $this->controller->loggedout($this->requestMock);
-
-
-        // Assertions to verify behavior
+        $this->controller->loggedout($request);
     }
 
-    public function testLogoutWithoutAuthSourceThrowsBadRequest(): void
+    #[DataProvider('requestMethod')]
+    public function testLogoutWithoutAuthSourceThrowsBadRequest(string $requestMethod): void
     {
-        $this->requestMock->query = $this->createQueryMock([]);
-        $this->requestMock->request = $this->createRequestMock([]);
+        $parameters = [
+            ...$this->parametersMock,
+        ];
+
+        $request = Request::create(
+            uri: 'https://localhost/auth/authorize',
+            method: $requestMethod,
+            parameters: $parameters,
+        );
 
         $this->expectException(BadRequest::class);
         $this->expectExceptionMessage('No authsource in the request');
 
-        $this->controller->logout($this->requestMock);
+        $this->controller->logout($request);
     }
 
-    public function testLogoutWithInvalidAuthSourceThrowsBadRequest(): void
+    #[DataProvider('requestMethod')]
+    public function testLogoutWithInvalidAuthSourceThrowsBadRequest(string $requestMethod): void
     {
-        $this->requestMock->query = $this->createQueryMock(['authSource' => '']);
-        $this->requestMock->request = $this->createRequestMock([]);
+        $parameters = [
+            'authSource' => ['INVALID SOURCE ID'],
+            ...$this->parametersMock,
+        ];
+
+        $request = Request::create(
+            uri: 'https://localhost/auth/authorize',
+            method: $requestMethod,
+            parameters: $parameters,
+        );
 
         $this->expectException(BadRequest::class);
         $this->expectExceptionMessage('Authsource ID invalid');
 
-        $this->controller->logout($this->requestMock);
+        $this->controller->logout($request);
     }
 
-    // Mock helper function
-    private function createQueryMock(array $params): InputBag
+    #[DataProvider('requestMethod')]
+    public function testSuccessfullLogout(string $requestMethod): void
     {
-        $queryMock = $this->getMockBuilder(InputBag::class)->getMock();
-        $queryMock->method('has')->willReturnCallback(
-            function (string $key) use ($params) {
-                return array_key_exists($key, $params);
-            }
+        $parameters = [
+            'authSource' => 'authsourceid',
+            ...$this->parametersMock,
+        ];
+
+        $request = Request::create(
+            uri: 'https://localhost/auth/authorize',
+            method: $requestMethod,
+            parameters: $parameters,
         );
 
-        $queryMock->method('get')->willReturnCallback(
-            function (?string $key) use ($params) {
-                return $params[$key] ?? null;
-            }
-        );
-        return $queryMock;
+        $logoutConfig = [
+            'oidc:localLogout' => true,
+            'ReturnTo' => '/' . RoutesEnum::Logout->value
+        ];
+
+        /** @psalm-suppress UndefinedMethod,MixedMethodCall */
+        $this->simpleMock
+            ->expects($this->once())
+            ->method('logout')
+            ->with($logoutConfig);
+
+        $this->controller->logout($request);
     }
 
     // Mock helper function
-    private function createRequestMock(array $params): InputBag
+    private function createControllerMock(array $methods): void
     {
-        $queryMock = $this->getMockBuilder(InputBag::class)->getMock();
+        $this->oauth2Mock = $this->getMockBuilder(OAuth2::class)
+            ->disableOriginalConstructor()
+            ->getMock();
 
-        $queryMock->method('get')->willReturnCallback(
-            function (?string $key) use ($params) {
-                return $params[$key] ?? null;
-            }
-        );
+        $this->simpleMock = $this->getMockBuilder(Simple::class)
+            ->disableOriginalConstructor()
+            ->onlyMethods(['logout'])
+            ->getMock();
 
-        $queryMock->method('all')->willReturnCallback(
-            function (?string $key) use ($params) {
-                return $params[$key] ?? [];
-            }
-        );
-        return $queryMock;
+        $this->sourceServiceMock = $this->getMockBuilder(SourceService::class)
+            ->onlyMethods(['completeLogout', 'getById'])
+            ->getMock();
+
+        $this->controller = $this->getMockBuilder(OIDCLogoutControllerMock::class)
+            ->onlyMethods($methods)
+            ->getMock();
+
+        /** @psalm-suppress UndefinedMethod,MixedMethodCall */
+        $this->controller
+            ->method('getSourceService')
+            ->willReturn($this->sourceServiceMock);
+
+        $this->controller
+            ->method('getAuthSource')
+            ->willReturn($this->simpleMock);
+
+        $this->sourceServiceMock
+            ->method('getById')
+            ->with('testSourceId', OAuth2::class)
+            ->willReturn($this->oauth2Mock);
+
+        $this->controller
+            ->method('loadState')
+            ->willReturn($this->stateMock);
     }
 }
diff --git a/tests/lib/Controller/Oauth2ControllerTest.php b/tests/lib/Controller/Oauth2ControllerTest.php
index 2dfaef1..b01f83a 100644
--- a/tests/lib/Controller/Oauth2ControllerTest.php
+++ b/tests/lib/Controller/Oauth2ControllerTest.php
@@ -6,8 +6,8 @@
 
 use DG\BypassFinals;
 use League\OAuth2\Client\Provider\Exception\IdentityProviderException;
+use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\TestCase;
-use SimpleSAML\Auth\Source;
 use SimpleSAML\Configuration;
 use SimpleSAML\Error\AuthSource;
 use SimpleSAML\Error\Exception;
@@ -20,7 +20,6 @@
 use SimpleSAML\Module\authoauth2\locators\SourceService;
 use SimpleSAML\Module\authoauth2\locators\SourceServiceLocator;
 use SimpleSAML\Utils\HTTP;
-use Symfony\Component\HttpFoundation\InputBag;
 use Symfony\Component\HttpFoundation\Request;
 
 // Unless we declare the class here, it is not recognized by phpcs
@@ -31,31 +30,6 @@ class Oauth2ControllerMock extends Oauth2Controller
     use RequestTrait;
     use ErrorTrait;
 
-    public function handleError(OAuth2 $source, array $state, Request $request): void
-    {
-        parent::handleError($source, $state, $request);
-    }
-
-    public function setSource(Source $source): void
-    {
-        $this->source = $source;
-    }
-
-    public function getSource(): ?Source
-    {
-        return $this->source;
-    }
-
-    public function setState(array $state): void
-    {
-        $this->state = $state;
-    }
-
-    public function setSourceId(string $sourceId): void
-    {
-        $this->sourceId = $sourceId;
-    }
-
     public function getExpectedStageState(): string
     {
         return $this->expectedStageState;
@@ -72,67 +46,110 @@ class Oauth2ControllerTest extends TestCase
 {
     /** @var Oauth2ControllerMock */
     private $controller;
-    /** @var Request */
-    private $requestMock;
     /** @var HTTP  */
     private $httpMock;
     /** @var \PHPUnit\Framework\MockObject\MockObject|(OAuth2&\PHPUnit\Framework\MockObject\MockObject) */
     private $oauth2Mock;
+    /** @var SourceService */
+    private $sourceServiceMock;
     private array $stateMock;
+    private array $parametersMock;
 
     protected function setUp(): void
     {
-        BypassFinals::enable(bypassReadOnly: false);
+        $this->oauth2Mock = $this->getMockBuilder(OAuth2::class)
+            ->disableOriginalConstructor()
+            ->onlyMethods(['finalStep', 'getConfig'])
+            ->getMock();
+        $this->sourceServiceMock = $this->getMockBuilder(SourceService::class)
+            ->onlyMethods(['getById', 'completeAuth'])
+            ->getMock();
+
 
-        $this->requestMock = $this->getMockBuilder(Request::class)->getMock();
-        $this->oauth2Mock = $this->getMockBuilder(OAuth2::class)->disableOriginalConstructor()->getMock();
         $this->httpMock = $this->getMockBuilder(HTTP::class)->getMock();
-        $this->stateMock = ['state' => 'testState'];
+        $this->parametersMock = ['state' => OAuth2::STATE_PREFIX . '|statefoo'];
+        $this->stateMock = [OAuth2::AUTHID => 'testSourceId'];
     }
 
     public function testExpectedConstVariables(): void
     {
-        $this->createControllerMock(['parseRequest', 'getSourceService', 'handleError', 'getHttp', 'parseError']);
+        $this->createControllerMock(['getSourceService', 'loadState']);
         $this->assertEquals(OAuth2::STAGE_INIT, $this->controller->getExpectedStageState());
         $this->assertEquals(OAuth2::STATE_PREFIX . '|', $this->controller->getExpectedPrefix());
     }
 
-    public function testLinkbackValidCode(): void
+    public static function requestMethod(): array
     {
-        $this->createControllerMock(['parseRequest', 'getSourceService', 'handleError', 'getHttp', 'parseError']);
-        $this->requestMock->query = $this->createQueryMock(['code' => 'validCode']);
+        return [
+            'GET' => ['GET'],
+            'POST' => ['POST'],
+        ];
+    }
+
+    #[DataProvider('requestMethod')]
+    public function testLinkbackValidCode(string $requestMethod): void
+    {
+        $this->createControllerMock(['getSourceService', 'loadState', 'getHttp']);
+        $parameters = [
+            'code' => 'validCode',
+            ...$this->parametersMock,
+        ];
+
+        $request = Request::create(
+            uri: 'https://localhost/auth/authorize',
+            method: $requestMethod,
+            parameters: $parameters,
+        );
 
         $this->oauth2Mock->expects($this->once())
             ->method('finalStep')
             ->with($this->stateMock, 'validCode');
 
-        /** @psalm-suppress UndefinedMethod,MixedMethodCall */
-        $this->controller
-            ->method('getSourceService')
-            ->willReturn($this->createMock(SourceService::class));
-
-        $this->controller->linkback($this->requestMock);
+        $this->sourceServiceMock->expects($this->once())
+            ->method('completeAuth')
+            ->with($this->stateMock);
 
-        // Assertions for the success scenario can be done here
+        $this->controller->linkback($request);
     }
 
-    public function testLinkbackWithNoCode(): void
+    #[DataProvider('requestMethod')]
+    public function testLinkbackWithNoCode(string $requestMethod): void
     {
-        $this->createControllerMock(['parseRequest', 'getSourceService', 'handleError', 'getHttp', 'parseError']);
-        $this->requestMock->query = $this->createQueryMock([]);
+        $this->createControllerMock(['getSourceService', 'loadState', 'handleError']);
+
+        $parameters = [
+            ...$this->parametersMock,
+        ];
+
+        $request = Request::create(
+            uri: 'https://localhost/auth/authorize',
+            method: $requestMethod,
+            parameters: $parameters,
+        );
 
         /** @psalm-suppress UndefinedMethod,MixedMethodCall */
         $this->controller
             ->expects($this->once())
             ->method('handleError');
 
-        $this->controller->linkback($this->requestMock);
+        $this->controller->linkback($request);
     }
 
-    public function testLinkbackWithIdentityProviderException(): void
+    #[DataProvider('requestMethod')]
+    public function testLinkbackWithIdentityProviderException(string $requestMethod): void
     {
-        $this->createControllerMock(['parseRequest', 'getSourceService', 'handleError', 'getHttp', 'parseError']);
-        $this->requestMock->query = $this->createQueryMock(['code' => 'validCode']);
+        $this->createControllerMock(['getSourceService', 'loadState', 'getHttp']);
+
+        $parameters = [
+            'code' => 'validCode',
+            ...$this->parametersMock,
+        ];
+
+        $request = Request::create(
+            uri: 'https://localhost/auth/authorize',
+            method: $requestMethod,
+            parameters: $parameters,
+        );
 
         $this->oauth2Mock->expects($this->once())
             ->method('finalStep')
@@ -140,36 +157,60 @@ public function testLinkbackWithIdentityProviderException(): void
 
         $this->expectException(AuthSource::class);
 
-        $this->controller->linkback($this->requestMock);
+        $this->controller->linkback($request);
+    }
+
+    public static function configuration(): array
+    {
+        return [ //datasets
+            'useConsentPage (GET)' => [ // dataset 0
+                [
+                    ['useConsentErrorPage' => true],
+                ],
+                'GET'
+            ],
+            'useConsentPage & legacyRoute (GET)' => [ // data set 1
+                [
+                    ['useConsentErrorPage' => true, 'useLegacyRoutes' => true],
+                ],
+                'GET'
+            ],
+            'useConsentPage (POST)' => [ // dataset 0
+                [
+                    ['useConsentErrorPage' => true],
+                ],
+                'POST'
+            ],
+            'useConsentPage & legacyRoute (POST)' => [ // data set 1
+                [
+                    ['useConsentErrorPage' => true, 'useLegacyRoutes' => true],
+                ],
+                'POST'
+            ],
+        ];
     }
 
     /**
      * @throws Exception
      */
-    public function testHandleErrorWithConsentedError(): void
+    #[DataProvider('configuration')]
+    public function testHandleErrorWithConsentedError(array $configuration, string $requestMethod): void
     {
-        $this->createControllerMock(['parseRequest', 'getSourceService', 'getHttp', 'parseError']);
-        $this->controller->getSource()->method('getAuthId')->willReturn('authId');
-        $this->controller
-            ->getSource()
-            ->method('getConfig')
-            ->willReturn(new class (['useConsentErrorPage' => true], '') extends Configuration {
-                public function getOptionalBoolean($name, $default): bool
-                {
-                    if (!$this->hasValue($name) && isset($default)) {
-                        return filter_var($default, FILTER_VALIDATE_BOOLEAN);
-                    }
-                    return filter_var($this->getValue($name), FILTER_VALIDATE_BOOLEAN);
-                }
-            });
-
-        $this->requestMock->query = $this->createQueryMock(
-            ['error' => 'invalid_scope', 'error_description' => 'Invalid scope']
+        $this->createControllerMock(['getSourceService', 'loadState', 'getHttp']);
+
+        $request = Request::create(
+            uri: 'https://localhost/auth/authorize',
+            method: $requestMethod,
+            parameters: [
+                     ...$this->parametersMock,
+                     'error' => 'invalid_scope',
+                     'error_description' => 'Invalid scope',
+                 ],
         );
 
-        $this->controller->method('parseError')
-            ->with($this->requestMock)
-            ->willReturn(['invalid_scope', 'Invalid scope']);
+        $this->oauth2Mock
+            ->method('getConfig')
+            ->willReturn(new Configuration($configuration, 'test'));
 
         $this->controller->method('getHttp')->willReturn($this->httpMock);
 
@@ -177,107 +218,91 @@ public function getOptionalBoolean($name, $default): bool
             ->method('redirectTrustedURL')
             ->with('http://localhost/module.php/authoauth2/errors/consent');
 
-        $this->controller->handleError($this->controller->getSource(), $this->stateMock, $this->requestMock);
+        $this->controller->linkback($request);
     }
 
-    public function testHandleErrorWithConsentErrorAtLegacyRoute(): void
+    public static function oauth2errors(): array
     {
-        $this->createControllerMock(['parseRequest', 'getSourceService', 'getHttp', 'parseError']);
-        $this->controller->getSource()->method('getAuthId')->willReturn('authId');
-        $configArray = ['useConsentErrorPage' => true, 'useLegacyRoutes' => true];
-        $this->controller
-            ->getSource()
-            ->method('getConfig')
-            ->willReturn(new Configuration($configArray, 'test'));
-
-        $this->requestMock->query = $this->createQueryMock(
-            ['error' => 'invalid_scope', 'error_description' => 'Invalid scope']
-        );
-
-        $this->controller->method('parseError')
-            ->with($this->requestMock)
-            ->willReturn(['invalid_scope', 'Invalid scope']);
-
-        $this->controller->method('getHttp')->willReturn($this->httpMock);
-
-        $this->httpMock->expects($this->once())
-            ->method('redirectTrustedURL')
-            ->with('http://localhost/module.php/authoauth2/errors/consent.php');
-
-        $this->controller->handleError($this->controller->getSource(), $this->stateMock, $this->requestMock);
+        return [
+          'oauth2 valid error code (GET)' => [
+              [
+                  'error' => 'invalid_scope',
+                  'error_description' => 'Invalid scope'
+              ],
+              UserAborted::class,
+              'GET'
+          ],
+          'oauth2 invalid error code (GET)' => [
+              [
+                  'error' => 'invalid_error',
+                  'error_description' => 'Invalid error'
+              ],
+              AuthSource::class,
+              'GET'
+          ],
+          'oauth2 valid error code (POST)' => [
+              [
+                  'error' => 'invalid_scope',
+                  'error_description' => 'Invalid scope'
+              ],
+              UserAborted::class,
+              'POST'
+          ],
+          'oauth2 invalid error code(POST)' => [
+              [
+                  'error' => 'invalid_error',
+                  'error_description' => 'Invalid error'
+              ],
+              AuthSource::class,
+              'POST'
+          ]
+        ];
     }
 
-    public function testHandleErrorWithUserAborted(): void
+    #[DataProvider('oauth2errors')]
+    public function testHandleErrorThrowException(array $errorResponse, string $className, string $requestMethod): void
     {
-        $this->createControllerMock(['parseRequest', 'getSourceService', 'getHttp', 'parseError']);
-        $this->controller->getSource()->method('getAuthId')->willReturn('authId');
+        $this->createControllerMock(['getSourceService', 'loadState', 'getHttp']);
+
+        $request = Request::create(
+            uri: 'https://localhost/auth/authorize',
+            method: $requestMethod,
+            parameters: [
+                     ...$this->parametersMock,
+                     ...$errorResponse,
+                 ],
+        );
         $configArray = ['useConsentErrorPage' => false];
-        $this->controller
-            ->getSource()
+
+        $this->oauth2Mock
             ->method('getConfig')
             ->willReturn(new Configuration($configArray, 'test'));
 
-        $this->requestMock->query = $this->createQueryMock(
-            ['error' => 'invalid_scope', 'error_description' => 'Invalid scope']
-        );
-
-        $this->controller->method('parseError')
-            ->with($this->requestMock)
-            ->willReturn(['invalid_scope', 'Invalid scope']);
-
-        $this->controller->method('getHttp')->willReturn($this->httpMock);
-
-        $this->expectException(UserAborted::class);
-
-        $this->controller->handleError($this->controller->getSource(), $this->stateMock, $this->requestMock);
-    }
-
-
-    public function testHandleErrorWithAuthSourceException(): void
-    {
-        $this->createControllerMock(['parseRequest', 'getSourceService', 'getHttp', 'parseError']);
-        $this->controller->getSource()->method('getAuthId')->willReturn('authId');
-
-        $this->requestMock->query = $this->createQueryMock(
-            ['error' => 'invalid_error', 'error_description' => 'Invalid Error']
-        );
-
-        $this->controller->method('parseError')
-            ->with($this->requestMock)
-            ->willReturn(['invalid_error', 'Invalid Error']);
-
         $this->controller->method('getHttp')->willReturn($this->httpMock);
 
-        $this->expectException(AuthSource::class);
+        $this->expectException($className);
 
-        $this->controller->handleError($this->controller->getSource(), $this->stateMock, $this->requestMock);
+        $this->controller->linkback($request);
     }
 
-    private function createControllerMock(array $methods): void
+    protected function createControllerMock(array $methods): void
     {
         $this->controller = $this->getMockBuilder(Oauth2ControllerMock::class)
             ->onlyMethods($methods)
             ->getMock();
 
-        // Stubbing dependencies
-        $this->controller->setSource($this->oauth2Mock);
-        $this->controller->setState($this->stateMock);
-        $this->controller->setSourceId('testSourceId');
-    }
+        /** @psalm-suppress UndefinedMethod,MixedMethodCall */
+        $this->controller
+            ->method('getSourceService')
+            ->willReturn($this->sourceServiceMock);
 
-    private function createQueryMock(array $params): InputBag
-    {
-        $queryMock = $this->getMockBuilder(InputBag::class)->getMock();
-        $queryMock->method('has')->willReturnCallback(
-            function (string $key) use ($params) {
-                return array_key_exists($key, $params);
-            }
-        );
-        $queryMock->method('get')->willReturnCallback(
-            function (string $key) use ($params) {
-                return $params[$key] ?? null;
-            }
-        );
-        return $queryMock;
+        $this->sourceServiceMock
+            ->method('getById')
+            ->with('testSourceId', OAuth2::class)
+            ->willReturn($this->oauth2Mock);
+
+        $this->controller
+            ->method('loadState')
+            ->willReturn($this->stateMock);
     }
 }
diff --git a/tests/lib/Controller/Trait/RequestTraitTest.php b/tests/lib/Controller/Trait/RequestTraitTest.php
index c0125ac..f5356de 100644
--- a/tests/lib/Controller/Trait/RequestTraitTest.php
+++ b/tests/lib/Controller/Trait/RequestTraitTest.php
@@ -147,7 +147,6 @@ public function testParseRequestWithEmptyAuthSourceId(): void
         $this->controller->parseRequest($this->request);
     }
 
-
     public function testParseRequestWithInvalidSource(): void
     {
         $this->request->query->set('state', OAuth2::STATE_PREFIX . '|valid_state_with_invalid_source');
@@ -166,4 +165,27 @@ public function testParseRequestWithInvalidSource(): void
 
         $this->controller->parseRequest($this->request);
     }
+
+    public function testParsePostGetRequest(): void
+    {
+        $request = Request::create(
+            uri: 'https://localhost/auth/authorize',
+            method: 'POST',
+            parameters: [ 'error' => 'invalid_request'],
+        );
+
+        $expected = ['error' => 'invalid_request'];
+
+        $this->parseRequestParamsSingleton($request);
+        $this->assertEquals($expected, $this->requestParams);
+
+        $request = Request::create(
+            uri: 'https://localhost/auth/authorize',
+            method: 'GET',
+            parameters: [ 'error' => 'invalid_request']
+        );
+
+        $this->parseRequestParamsSingleton($request);
+        $this->assertEquals($expected, $this->requestParams);
+    }
 }