diff --git a/config/corppass-login.php b/config/corppass-login.php
index 9c08e59..0d8713c 100644
--- a/config/corppass-login.php
+++ b/config/corppass-login.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use Accredifysg\SingPassLogin\Http\Controllers\CorpPass\LoginCallbackController;
 use Accredifysg\SingPassLogin\Http\Controllers\CorpPass\LoginController;
 use Accredifysg\SingPassLogin\Listeners\CorpPassSuccessfulLoginListener;
diff --git a/config/myinfo.php b/config/myinfo.php
index 60d600b..587c73b 100644
--- a/config/myinfo.php
+++ b/config/myinfo.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use Accredifysg\SingPassLogin\Http\Controllers\SingPass\MyInfoCallbackController;
 use Accredifysg\SingPassLogin\Http\Controllers\SingPass\MyInfoController;
 
diff --git a/config/ndi.php b/config/ndi.php
index 99ebfcd..2f86d98 100644
--- a/config/ndi.php
+++ b/config/ndi.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use Accredifysg\SingPassLogin\Http\Controllers\GetJwksEndpointController;
 
 return [
diff --git a/config/singpass-login.php b/config/singpass-login.php
index 3bbd07e..4fa5421 100644
--- a/config/singpass-login.php
+++ b/config/singpass-login.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use Accredifysg\SingPassLogin\Http\Controllers\SingPass\LoginCallbackController;
 use Accredifysg\SingPassLogin\Http\Controllers\SingPass\LoginController;
 use Accredifysg\SingPassLogin\Listeners\SingPassSuccessfulLoginListener;
diff --git a/database/factories/UserFactory.php b/database/factories/UserFactory.php
index d325869..e8de1f5 100644
--- a/database/factories/UserFactory.php
+++ b/database/factories/UserFactory.php
@@ -1,10 +1,11 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Database\Factories;
 
 use Accredifysg\SingPassLogin\Models\User;
 use Illuminate\Database\Eloquent\Factories\Factory;
-use Illuminate\Database\Eloquent\Model;
 use Illuminate\Support\Str;
 
 /**
diff --git a/database/migrations/add_corppass_entity_id_to_users_table.php b/database/migrations/add_corppass_entity_id_to_users_table.php
index cd28997..0c1d095 100644
--- a/database/migrations/add_corppass_entity_id_to_users_table.php
+++ b/database/migrations/add_corppass_entity_id_to_users_table.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use Illuminate\Database\Migrations\Migration;
 use Illuminate\Support\Facades\Schema;
 
diff --git a/database/migrations/add_nric_to_users_table.php b/database/migrations/add_nric_to_users_table.php
index 3b4bc69..17d70d2 100644
--- a/database/migrations/add_nric_to_users_table.php
+++ b/database/migrations/add_nric_to_users_table.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use Illuminate\Database\Migrations\Migration;
 use Illuminate\Support\Facades\Schema;
 
diff --git a/routes/web.php b/routes/web.php
index 0ac8026..3d28c26 100644
--- a/routes/web.php
+++ b/routes/web.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use Illuminate\Support\Facades\Route;
 
 Route::middleware('web')->group(function () {
diff --git a/src/DTOs/FapiCallbackResult.php b/src/DTOs/FapiCallbackResult.php
index b46d6fc..fccc26a 100644
--- a/src/DTOs/FapiCallbackResult.php
+++ b/src/DTOs/FapiCallbackResult.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\DTOs;
 
 readonly class FapiCallbackResult
diff --git a/src/DTOs/FapiSessionContext.php b/src/DTOs/FapiSessionContext.php
index 68b58c3..d5cbdf3 100644
--- a/src/DTOs/FapiSessionContext.php
+++ b/src/DTOs/FapiSessionContext.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\DTOs;
 
 use Jose\Component\Core\JWK;
diff --git a/src/DTOs/OpenIdConfigurationDto.php b/src/DTOs/OpenIdConfigurationDto.php
index 96ecae6..7b9ef1f 100644
--- a/src/DTOs/OpenIdConfigurationDto.php
+++ b/src/DTOs/OpenIdConfigurationDto.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\DTOs;
 
 use Accredifysg\SingPassLogin\Exceptions\OpenIdDiscoveryException;
diff --git a/src/DTOs/ProviderConfig.php b/src/DTOs/ProviderConfig.php
index cefef38..d14769b 100644
--- a/src/DTOs/ProviderConfig.php
+++ b/src/DTOs/ProviderConfig.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\DTOs;
 
 use Accredifysg\SingPassLogin\Exceptions\MissingConfigException;
diff --git a/src/DTOs/TokenResponseDto.php b/src/DTOs/TokenResponseDto.php
index 90c6263..649921b 100644
--- a/src/DTOs/TokenResponseDto.php
+++ b/src/DTOs/TokenResponseDto.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\DTOs;
 
 readonly class TokenResponseDto
diff --git a/src/Events/CorpPassDataRetrievedEvent.php b/src/Events/CorpPassDataRetrievedEvent.php
index d1a9b45..85fb690 100644
--- a/src/Events/CorpPassDataRetrievedEvent.php
+++ b/src/Events/CorpPassDataRetrievedEvent.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Events;
 
 readonly class CorpPassDataRetrievedEvent
diff --git a/src/Events/CorpPassSuccessfulLoginEvent.php b/src/Events/CorpPassSuccessfulLoginEvent.php
index 8ae4535..1efb367 100644
--- a/src/Events/CorpPassSuccessfulLoginEvent.php
+++ b/src/Events/CorpPassSuccessfulLoginEvent.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Events;
 
 use Accredifysg\SingPassLogin\Models\CorpPassUser;
diff --git a/src/Events/MyInfoDataRetrievedEvent.php b/src/Events/MyInfoDataRetrievedEvent.php
index 91bbb88..8665a56 100644
--- a/src/Events/MyInfoDataRetrievedEvent.php
+++ b/src/Events/MyInfoDataRetrievedEvent.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Events;
 
 /**
diff --git a/src/Events/SingPassSuccessfulLoginEvent.php b/src/Events/SingPassSuccessfulLoginEvent.php
index 143efe3..8a93354 100644
--- a/src/Events/SingPassSuccessfulLoginEvent.php
+++ b/src/Events/SingPassSuccessfulLoginEvent.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Events;
 
 use Accredifysg\SingPassLogin\Models\SingPassUser;
diff --git a/src/Exceptions/AuthFlowException.php b/src/Exceptions/AuthFlowException.php
index 09c4d85..f306510 100644
--- a/src/Exceptions/AuthFlowException.php
+++ b/src/Exceptions/AuthFlowException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/AuthenticationErrorException.php b/src/Exceptions/AuthenticationErrorException.php
index 8cd447b..f274ee4 100644
--- a/src/Exceptions/AuthenticationErrorException.php
+++ b/src/Exceptions/AuthenticationErrorException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/CorpPassLoginException.php b/src/Exceptions/CorpPassLoginException.php
index 87c273a..908ab68 100644
--- a/src/Exceptions/CorpPassLoginException.php
+++ b/src/Exceptions/CorpPassLoginException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/JweDecryptionFailedException.php b/src/Exceptions/JweDecryptionFailedException.php
index a4ac10e..7424c3b 100644
--- a/src/Exceptions/JweDecryptionFailedException.php
+++ b/src/Exceptions/JweDecryptionFailedException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/JwksException.php b/src/Exceptions/JwksException.php
index b5c4f26..c94158a 100644
--- a/src/Exceptions/JwksException.php
+++ b/src/Exceptions/JwksException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/JwksInvalidException.php b/src/Exceptions/JwksInvalidException.php
index cf53fc6..66708f5 100644
--- a/src/Exceptions/JwksInvalidException.php
+++ b/src/Exceptions/JwksInvalidException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/JwtDecodeFailedException.php b/src/Exceptions/JwtDecodeFailedException.php
index 09ca623..7bce923 100644
--- a/src/Exceptions/JwtDecodeFailedException.php
+++ b/src/Exceptions/JwtDecodeFailedException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/JwtPayloadException.php b/src/Exceptions/JwtPayloadException.php
index 368260c..7cc6947 100644
--- a/src/Exceptions/JwtPayloadException.php
+++ b/src/Exceptions/JwtPayloadException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/MissingConfigException.php b/src/Exceptions/MissingConfigException.php
index 1ff99f7..d8c260d 100644
--- a/src/Exceptions/MissingConfigException.php
+++ b/src/Exceptions/MissingConfigException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use RuntimeException;
diff --git a/src/Exceptions/OpenIdDiscoveryException.php b/src/Exceptions/OpenIdDiscoveryException.php
index f09e2bd..3bf5ac7 100644
--- a/src/Exceptions/OpenIdDiscoveryException.php
+++ b/src/Exceptions/OpenIdDiscoveryException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/PushedAuthorizationRequestException.php b/src/Exceptions/PushedAuthorizationRequestException.php
index 30eee0b..b1aa650 100644
--- a/src/Exceptions/PushedAuthorizationRequestException.php
+++ b/src/Exceptions/PushedAuthorizationRequestException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/SingPassLoginException.php b/src/Exceptions/SingPassLoginException.php
index a843315..decbfc9 100644
--- a/src/Exceptions/SingPassLoginException.php
+++ b/src/Exceptions/SingPassLoginException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/TokenExchangeException.php b/src/Exceptions/TokenExchangeException.php
index 8354c28..99e9bc5 100644
--- a/src/Exceptions/TokenExchangeException.php
+++ b/src/Exceptions/TokenExchangeException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/UserInfoDecryptionException.php b/src/Exceptions/UserInfoDecryptionException.php
index 10f36f4..c0c701c 100644
--- a/src/Exceptions/UserInfoDecryptionException.php
+++ b/src/Exceptions/UserInfoDecryptionException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/UserInfoRequestException.php b/src/Exceptions/UserInfoRequestException.php
index a2051ea..2cb3546 100644
--- a/src/Exceptions/UserInfoRequestException.php
+++ b/src/Exceptions/UserInfoRequestException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/UserInfoVerificationException.php b/src/Exceptions/UserInfoVerificationException.php
index b0c2b28..61a6c8f 100644
--- a/src/Exceptions/UserInfoVerificationException.php
+++ b/src/Exceptions/UserInfoVerificationException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Exceptions;
 
 use Exception;
diff --git a/src/Http/Controllers/CorpPass/LoginCallbackController.php b/src/Http/Controllers/CorpPass/LoginCallbackController.php
index 3f3f442..ccf936e 100644
--- a/src/Http/Controllers/CorpPass/LoginCallbackController.php
+++ b/src/Http/Controllers/CorpPass/LoginCallbackController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Http\Controllers\CorpPass;
 
 use Accredifysg\SingPassLogin\DTOs\ProviderConfig;
diff --git a/src/Http/Controllers/CorpPass/LoginController.php b/src/Http/Controllers/CorpPass/LoginController.php
index b47bc82..9fd3894 100644
--- a/src/Http/Controllers/CorpPass/LoginController.php
+++ b/src/Http/Controllers/CorpPass/LoginController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Http\Controllers\CorpPass;
 
 use Accredifysg\SingPassLogin\DTOs\ProviderConfig;
diff --git a/src/Http/Controllers/GetJwksEndpointController.php b/src/Http/Controllers/GetJwksEndpointController.php
index ca623ec..bd32653 100644
--- a/src/Http/Controllers/GetJwksEndpointController.php
+++ b/src/Http/Controllers/GetJwksEndpointController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Http\Controllers;
 
 use Accredifysg\SingPassLogin\Exceptions\JwksInvalidException;
diff --git a/src/Http/Controllers/SingPass/LoginCallbackController.php b/src/Http/Controllers/SingPass/LoginCallbackController.php
index 673554b..8c9b759 100644
--- a/src/Http/Controllers/SingPass/LoginCallbackController.php
+++ b/src/Http/Controllers/SingPass/LoginCallbackController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Http\Controllers\SingPass;
 
 use Accredifysg\SingPassLogin\DTOs\ProviderConfig;
diff --git a/src/Http/Controllers/SingPass/LoginController.php b/src/Http/Controllers/SingPass/LoginController.php
index e8c69c9..c550716 100644
--- a/src/Http/Controllers/SingPass/LoginController.php
+++ b/src/Http/Controllers/SingPass/LoginController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Http\Controllers\SingPass;
 
 use Accredifysg\SingPassLogin\DTOs\ProviderConfig;
diff --git a/src/Http/Controllers/SingPass/MyInfoCallbackController.php b/src/Http/Controllers/SingPass/MyInfoCallbackController.php
index b634946..500100e 100644
--- a/src/Http/Controllers/SingPass/MyInfoCallbackController.php
+++ b/src/Http/Controllers/SingPass/MyInfoCallbackController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Http\Controllers\SingPass;
 
 use Accredifysg\SingPassLogin\DTOs\ProviderConfig;
diff --git a/src/Http/Controllers/SingPass/MyInfoController.php b/src/Http/Controllers/SingPass/MyInfoController.php
index 9d8b0ca..08a34fd 100644
--- a/src/Http/Controllers/SingPass/MyInfoController.php
+++ b/src/Http/Controllers/SingPass/MyInfoController.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Http\Controllers\SingPass;
 
 use Accredifysg\SingPassLogin\DTOs\ProviderConfig;
diff --git a/src/Interfaces/CodeChallengeVerifierServiceInterface.php b/src/Interfaces/CodeChallengeVerifierServiceInterface.php
index 8cb92ed..e9d4e37 100644
--- a/src/Interfaces/CodeChallengeVerifierServiceInterface.php
+++ b/src/Interfaces/CodeChallengeVerifierServiceInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Interfaces;
 
 interface CodeChallengeVerifierServiceInterface
diff --git a/src/Interfaces/DPoPServiceInterface.php b/src/Interfaces/DPoPServiceInterface.php
index 961046d..486a86e 100644
--- a/src/Interfaces/DPoPServiceInterface.php
+++ b/src/Interfaces/DPoPServiceInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Interfaces;
 
 use Jose\Component\Core\JWK;
diff --git a/src/Interfaces/GetUserInfoServiceInterface.php b/src/Interfaces/GetUserInfoServiceInterface.php
index b3ccd7a..fbee976 100644
--- a/src/Interfaces/GetUserInfoServiceInterface.php
+++ b/src/Interfaces/GetUserInfoServiceInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Interfaces;
 
 use Jose\Component\Core\JWK;
diff --git a/src/Interfaces/JwksServiceInterface.php b/src/Interfaces/JwksServiceInterface.php
index 2118afb..a48ceca 100644
--- a/src/Interfaces/JwksServiceInterface.php
+++ b/src/Interfaces/JwksServiceInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Interfaces;
 
 use Jose\Component\Core\JWKSet;
diff --git a/src/Interfaces/JwtServiceInterface.php b/src/Interfaces/JwtServiceInterface.php
index cf061dc..a1b6d3f 100644
--- a/src/Interfaces/JwtServiceInterface.php
+++ b/src/Interfaces/JwtServiceInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Interfaces;
 
 use Jose\Component\Core\JWKSet;
diff --git a/src/Interfaces/OpenIdDiscoveryServiceInterface.php b/src/Interfaces/OpenIdDiscoveryServiceInterface.php
index 8d7f6f5..afbeba8 100644
--- a/src/Interfaces/OpenIdDiscoveryServiceInterface.php
+++ b/src/Interfaces/OpenIdDiscoveryServiceInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Interfaces;
 
 interface OpenIdDiscoveryServiceInterface
diff --git a/src/Interfaces/PushedAuthorizationRequestServiceInterface.php b/src/Interfaces/PushedAuthorizationRequestServiceInterface.php
index 4403d7f..04ca755 100644
--- a/src/Interfaces/PushedAuthorizationRequestServiceInterface.php
+++ b/src/Interfaces/PushedAuthorizationRequestServiceInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Interfaces;
 
 interface PushedAuthorizationRequestServiceInterface
diff --git a/src/Interfaces/TokenExchangeServiceInterface.php b/src/Interfaces/TokenExchangeServiceInterface.php
index 401410f..9e0ce14 100644
--- a/src/Interfaces/TokenExchangeServiceInterface.php
+++ b/src/Interfaces/TokenExchangeServiceInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Interfaces;
 
 use Accredifysg\SingPassLogin\DTOs\TokenResponseDto;
diff --git a/src/Listeners/CorpPassSuccessfulLoginListener.php b/src/Listeners/CorpPassSuccessfulLoginListener.php
index b1abcf1..0ba3411 100644
--- a/src/Listeners/CorpPassSuccessfulLoginListener.php
+++ b/src/Listeners/CorpPassSuccessfulLoginListener.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Listeners;
 
 use Accredifysg\SingPassLogin\Events\CorpPassSuccessfulLoginEvent;
diff --git a/src/Listeners/SingPassSuccessfulLoginListener.php b/src/Listeners/SingPassSuccessfulLoginListener.php
index 8a606b5..e8eeeb8 100644
--- a/src/Listeners/SingPassSuccessfulLoginListener.php
+++ b/src/Listeners/SingPassSuccessfulLoginListener.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Listeners;
 
 use Accredifysg\SingPassLogin\Events\SingPassSuccessfulLoginEvent;
diff --git a/src/Models/CorpPassUser.php b/src/Models/CorpPassUser.php
index e391d3a..afef79a 100644
--- a/src/Models/CorpPassUser.php
+++ b/src/Models/CorpPassUser.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Models;
 
 use Accredifysg\SingPassLogin\Exceptions\JwtPayloadException;
diff --git a/src/Models/SingPassUser.php b/src/Models/SingPassUser.php
index 06cdc34..493da32 100644
--- a/src/Models/SingPassUser.php
+++ b/src/Models/SingPassUser.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Models;
 
 use Accredifysg\SingPassLogin\Exceptions\JwtPayloadException;
diff --git a/src/Models/User.php b/src/Models/User.php
index 8657c97..b2211f0 100644
--- a/src/Models/User.php
+++ b/src/Models/User.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Models;
 
 use Accredifysg\SingPassLogin\Database\Factories\UserFactory;
diff --git a/src/Services/CodeChallengeVerifierService.php b/src/Services/CodeChallengeVerifierService.php
index cd0d8f9..e24d974 100644
--- a/src/Services/CodeChallengeVerifierService.php
+++ b/src/Services/CodeChallengeVerifierService.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Services;
 
 use Accredifysg\SingPassLogin\Interfaces\CodeChallengeVerifierServiceInterface;
diff --git a/src/Services/DPoPService.php b/src/Services/DPoPService.php
index 5a88feb..b46af10 100644
--- a/src/Services/DPoPService.php
+++ b/src/Services/DPoPService.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Services;
 
 use Accredifysg\SingPassLogin\Interfaces\DPoPServiceInterface;
diff --git a/src/Services/FapiAuthenticationService.php b/src/Services/FapiAuthenticationService.php
index b108ec0..e822323 100644
--- a/src/Services/FapiAuthenticationService.php
+++ b/src/Services/FapiAuthenticationService.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Services;
 
 use Accredifysg\SingPassLogin\DTOs\OpenIdConfigurationDto;
diff --git a/src/Services/FapiCallbackService.php b/src/Services/FapiCallbackService.php
index 672e7e0..432f717 100644
--- a/src/Services/FapiCallbackService.php
+++ b/src/Services/FapiCallbackService.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Services;
 
 use Accredifysg\SingPassLogin\DTOs\FapiCallbackResult;
diff --git a/src/Services/GetUserInfoService.php b/src/Services/GetUserInfoService.php
index 07bccbd..cdb87b4 100644
--- a/src/Services/GetUserInfoService.php
+++ b/src/Services/GetUserInfoService.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Services;
 
 use Accredifysg\SingPassLogin\DTOs\OpenIdConfigurationDto;
diff --git a/src/Services/JwksService.php b/src/Services/JwksService.php
index 55e7626..2dfa9f0 100644
--- a/src/Services/JwksService.php
+++ b/src/Services/JwksService.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Services;
 
 use Accredifysg\SingPassLogin\DTOs\OpenIdConfigurationDto;
diff --git a/src/Services/JwtService.php b/src/Services/JwtService.php
index 4aa4682..ae35883 100644
--- a/src/Services/JwtService.php
+++ b/src/Services/JwtService.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Services;
 
 use Accredifysg\SingPassLogin\Exceptions\JweDecryptionFailedException;
diff --git a/src/Services/OpenIdDiscoveryService.php b/src/Services/OpenIdDiscoveryService.php
index 98a18e7..e2b7c9a 100644
--- a/src/Services/OpenIdDiscoveryService.php
+++ b/src/Services/OpenIdDiscoveryService.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Services;
 
 use Accredifysg\SingPassLogin\DTOs\OpenIdConfigurationDto;
diff --git a/src/Services/PushedAuthorizationRequestService.php b/src/Services/PushedAuthorizationRequestService.php
index fd1522d..f3ae692 100644
--- a/src/Services/PushedAuthorizationRequestService.php
+++ b/src/Services/PushedAuthorizationRequestService.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Services;
 
 use Accredifysg\SingPassLogin\DTOs\OpenIdConfigurationDto;
diff --git a/src/Services/ScopeValidationService.php b/src/Services/ScopeValidationService.php
index f90bb77..aa9415b 100644
--- a/src/Services/ScopeValidationService.php
+++ b/src/Services/ScopeValidationService.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Services;
 
 use InvalidArgumentException;
diff --git a/src/Services/TokenExchangeService.php b/src/Services/TokenExchangeService.php
index 740e8a0..953f0ab 100644
--- a/src/Services/TokenExchangeService.php
+++ b/src/Services/TokenExchangeService.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Services;
 
 use Accredifysg\SingPassLogin\DTOs\OpenIdConfigurationDto;
diff --git a/src/SingPassLoginServiceProvider.php b/src/SingPassLoginServiceProvider.php
index 5799eb2..ea4759c 100644
--- a/src/SingPassLoginServiceProvider.php
+++ b/src/SingPassLoginServiceProvider.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin;
 
 use Accredifysg\SingPassLogin\Events\CorpPassSuccessfulLoginEvent;
diff --git a/src/Support/SingPassLog.php b/src/Support/SingPassLog.php
index 97f4e6f..f2c4c85 100644
--- a/src/Support/SingPassLog.php
+++ b/src/Support/SingPassLog.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Support;
 
 use Illuminate\Support\Facades\Log;
diff --git a/tests/TestCase.php b/tests/TestCase.php
index f421c37..7d18def 100644
--- a/tests/TestCase.php
+++ b/tests/TestCase.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests;
 
 use Accredifysg\SingPassLogin\SingPassLoginServiceProvider;
diff --git a/tests/Unit/DTOs/OpenIdConfigurationDtoTest.php b/tests/Unit/DTOs/OpenIdConfigurationDtoTest.php
index 5bfbb89..2790868 100644
--- a/tests/Unit/DTOs/OpenIdConfigurationDtoTest.php
+++ b/tests/Unit/DTOs/OpenIdConfigurationDtoTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\DTOs;
 
 use Accredifysg\SingPassLogin\DTOs\OpenIdConfigurationDto;
diff --git a/tests/Unit/DTOs/ProviderConfigTest.php b/tests/Unit/DTOs/ProviderConfigTest.php
index 190b674..89acf1e 100644
--- a/tests/Unit/DTOs/ProviderConfigTest.php
+++ b/tests/Unit/DTOs/ProviderConfigTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\DTOs;
 
 use Accredifysg\SingPassLogin\DTOs\ProviderConfig;
diff --git a/tests/Unit/Events/CorpPassDataRetrievedEventTest.php b/tests/Unit/Events/CorpPassDataRetrievedEventTest.php
index 0ff253f..dc94b07 100644
--- a/tests/Unit/Events/CorpPassDataRetrievedEventTest.php
+++ b/tests/Unit/Events/CorpPassDataRetrievedEventTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Events;
 
 use Accredifysg\SingPassLogin\Events\CorpPassDataRetrievedEvent;
diff --git a/tests/Unit/Events/CorpPassSuccessfulLoginEventTest.php b/tests/Unit/Events/CorpPassSuccessfulLoginEventTest.php
index e9fc881..4295850 100644
--- a/tests/Unit/Events/CorpPassSuccessfulLoginEventTest.php
+++ b/tests/Unit/Events/CorpPassSuccessfulLoginEventTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Events;
 
 use Accredifysg\SingPassLogin\Events\CorpPassSuccessfulLoginEvent;
diff --git a/tests/Unit/Events/SingPassSuccessfulLoginEventTest.php b/tests/Unit/Events/SingPassSuccessfulLoginEventTest.php
index 88ea33c..3407a00 100644
--- a/tests/Unit/Events/SingPassSuccessfulLoginEventTest.php
+++ b/tests/Unit/Events/SingPassSuccessfulLoginEventTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Events;
 
 use Accredifysg\SingPassLogin\Events\SingPassSuccessfulLoginEvent;
diff --git a/tests/Unit/Exceptions/JweDecryptionFailedExceptionTest.php b/tests/Unit/Exceptions/JweDecryptionFailedExceptionTest.php
index ab138f9..85f8037 100644
--- a/tests/Unit/Exceptions/JweDecryptionFailedExceptionTest.php
+++ b/tests/Unit/Exceptions/JweDecryptionFailedExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Exceptions;
 
 use Accredifysg\SingPassLogin\Exceptions\JweDecryptionFailedException;
diff --git a/tests/Unit/Exceptions/JwksExceptionTest.php b/tests/Unit/Exceptions/JwksExceptionTest.php
index c71e676..af31446 100644
--- a/tests/Unit/Exceptions/JwksExceptionTest.php
+++ b/tests/Unit/Exceptions/JwksExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Exceptions;
 
 use Accredifysg\SingPassLogin\Exceptions\JwksException;
diff --git a/tests/Unit/Exceptions/JwksInvalidExceptionTest.php b/tests/Unit/Exceptions/JwksInvalidExceptionTest.php
index 6a3d292..f3749b7 100644
--- a/tests/Unit/Exceptions/JwksInvalidExceptionTest.php
+++ b/tests/Unit/Exceptions/JwksInvalidExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Exceptions;
 
 use Accredifysg\SingPassLogin\Exceptions\JwksInvalidException;
diff --git a/tests/Unit/Exceptions/JwtDecodeFailedExceptionTest.php b/tests/Unit/Exceptions/JwtDecodeFailedExceptionTest.php
index db2a855..681d002 100644
--- a/tests/Unit/Exceptions/JwtDecodeFailedExceptionTest.php
+++ b/tests/Unit/Exceptions/JwtDecodeFailedExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Exceptions;
 
 use Accredifysg\SingPassLogin\Exceptions\JwtDecodeFailedException;
diff --git a/tests/Unit/Exceptions/JwtPayloadExceptionTest.php b/tests/Unit/Exceptions/JwtPayloadExceptionTest.php
index eb5f61e..c568c84 100644
--- a/tests/Unit/Exceptions/JwtPayloadExceptionTest.php
+++ b/tests/Unit/Exceptions/JwtPayloadExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Exceptions;
 
 use Accredifysg\SingPassLogin\Exceptions\JwtPayloadException;
diff --git a/tests/Unit/Exceptions/OpenIdDiscoveryExceptionTest.php b/tests/Unit/Exceptions/OpenIdDiscoveryExceptionTest.php
index faf06d7..35b00ae 100644
--- a/tests/Unit/Exceptions/OpenIdDiscoveryExceptionTest.php
+++ b/tests/Unit/Exceptions/OpenIdDiscoveryExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Exceptions;
 
 use Accredifysg\SingPassLogin\Exceptions\OpenIdDiscoveryException;
diff --git a/tests/Unit/Exceptions/SingPassLoginExceptionTest.php b/tests/Unit/Exceptions/SingPassLoginExceptionTest.php
index a8a770d..f0563f1 100644
--- a/tests/Unit/Exceptions/SingPassLoginExceptionTest.php
+++ b/tests/Unit/Exceptions/SingPassLoginExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Exceptions;
 
 use Accredifysg\SingPassLogin\Exceptions\SingPassLoginException;
diff --git a/tests/Unit/Exceptions/TokenExchangeExceptionTest.php b/tests/Unit/Exceptions/TokenExchangeExceptionTest.php
index e663166..00598ec 100644
--- a/tests/Unit/Exceptions/TokenExchangeExceptionTest.php
+++ b/tests/Unit/Exceptions/TokenExchangeExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Exceptions;
 
 use Accredifysg\SingPassLogin\Exceptions\TokenExchangeException;
diff --git a/tests/Unit/Exceptions/UserInfoDecryptionExceptionTest.php b/tests/Unit/Exceptions/UserInfoDecryptionExceptionTest.php
index 40dc979..fe65b95 100644
--- a/tests/Unit/Exceptions/UserInfoDecryptionExceptionTest.php
+++ b/tests/Unit/Exceptions/UserInfoDecryptionExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Exceptions;
 
 use Accredifysg\SingPassLogin\Exceptions\UserInfoDecryptionException;
diff --git a/tests/Unit/Exceptions/UserInfoRequestExceptionTest.php b/tests/Unit/Exceptions/UserInfoRequestExceptionTest.php
index 3da6e75..0477c3c 100644
--- a/tests/Unit/Exceptions/UserInfoRequestExceptionTest.php
+++ b/tests/Unit/Exceptions/UserInfoRequestExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Exceptions;
 
 use Accredifysg\SingPassLogin\Exceptions\UserInfoRequestException;
diff --git a/tests/Unit/Exceptions/UserInfoVerificationExceptionTest.php b/tests/Unit/Exceptions/UserInfoVerificationExceptionTest.php
index 4c9bbaf..4dd5ea8 100644
--- a/tests/Unit/Exceptions/UserInfoVerificationExceptionTest.php
+++ b/tests/Unit/Exceptions/UserInfoVerificationExceptionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Exceptions;
 
 use Accredifysg\SingPassLogin\Exceptions\UserInfoVerificationException;
diff --git a/tests/Unit/GetSingPassUserTest.php b/tests/Unit/GetSingPassUserTest.php
index cba1522..2845d15 100644
--- a/tests/Unit/GetSingPassUserTest.php
+++ b/tests/Unit/GetSingPassUserTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit;
 
 use Accredifysg\SingPassLogin\Exceptions\JwtPayloadException;
diff --git a/tests/Unit/Http/Controllers/CorpPass/LoginCallbackControllerTest.php b/tests/Unit/Http/Controllers/CorpPass/LoginCallbackControllerTest.php
index f9da372..81e58cf 100644
--- a/tests/Unit/Http/Controllers/CorpPass/LoginCallbackControllerTest.php
+++ b/tests/Unit/Http/Controllers/CorpPass/LoginCallbackControllerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Http\Controllers\CorpPass;
 
 use Accredifysg\SingPassLogin\DTOs\FapiCallbackResult;
diff --git a/tests/Unit/Http/Controllers/CorpPass/LoginControllerTest.php b/tests/Unit/Http/Controllers/CorpPass/LoginControllerTest.php
index 6790433..e0b6f7d 100644
--- a/tests/Unit/Http/Controllers/CorpPass/LoginControllerTest.php
+++ b/tests/Unit/Http/Controllers/CorpPass/LoginControllerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Http\Controllers\CorpPass;
 
 use Accredifysg\SingPassLogin\Services\FapiAuthenticationService;
diff --git a/tests/Unit/Http/Controllers/GetJwksEndpointControllerTest.php b/tests/Unit/Http/Controllers/GetJwksEndpointControllerTest.php
index 30f0a6c..1cd31ef 100644
--- a/tests/Unit/Http/Controllers/GetJwksEndpointControllerTest.php
+++ b/tests/Unit/Http/Controllers/GetJwksEndpointControllerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Http\Controllers;
 
 use Accredifysg\SingPassLogin\Exceptions\JwksInvalidException;
diff --git a/tests/Unit/Http/Controllers/SingPass/LoginCallbackControllerTest.php b/tests/Unit/Http/Controllers/SingPass/LoginCallbackControllerTest.php
index 25bbe43..b2ac89b 100644
--- a/tests/Unit/Http/Controllers/SingPass/LoginCallbackControllerTest.php
+++ b/tests/Unit/Http/Controllers/SingPass/LoginCallbackControllerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Http\Controllers\SingPass;
 
 use Accredifysg\SingPassLogin\DTOs\FapiCallbackResult;
diff --git a/tests/Unit/Http/Controllers/SingPass/LoginControllerTest.php b/tests/Unit/Http/Controllers/SingPass/LoginControllerTest.php
index be69ead..5d17a1e 100644
--- a/tests/Unit/Http/Controllers/SingPass/LoginControllerTest.php
+++ b/tests/Unit/Http/Controllers/SingPass/LoginControllerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Http\Controllers\SingPass;
 
 use Accredifysg\SingPassLogin\Services\FapiAuthenticationService;
diff --git a/tests/Unit/Http/Controllers/SingPass/MyInfoCallbackControllerTest.php b/tests/Unit/Http/Controllers/SingPass/MyInfoCallbackControllerTest.php
index 7e082cb..7e8c0d0 100644
--- a/tests/Unit/Http/Controllers/SingPass/MyInfoCallbackControllerTest.php
+++ b/tests/Unit/Http/Controllers/SingPass/MyInfoCallbackControllerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Http\Controllers\SingPass;
 
 use Accredifysg\SingPassLogin\DTOs\FapiCallbackResult;
diff --git a/tests/Unit/Http/Controllers/SingPass/MyInfoControllerTest.php b/tests/Unit/Http/Controllers/SingPass/MyInfoControllerTest.php
index 012e980..eee3c1a 100644
--- a/tests/Unit/Http/Controllers/SingPass/MyInfoControllerTest.php
+++ b/tests/Unit/Http/Controllers/SingPass/MyInfoControllerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Http\Controllers\SingPass;
 
 use Accredifysg\SingPassLogin\Services\FapiAuthenticationService;
diff --git a/tests/Unit/Listeners/CorpPassSuccessfulLoginListenerTest.php b/tests/Unit/Listeners/CorpPassSuccessfulLoginListenerTest.php
index efafd9e..282c93f 100644
--- a/tests/Unit/Listeners/CorpPassSuccessfulLoginListenerTest.php
+++ b/tests/Unit/Listeners/CorpPassSuccessfulLoginListenerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Listeners;
 
 use Accredifysg\SingPassLogin\Events\CorpPassSuccessfulLoginEvent;
diff --git a/tests/Unit/Listeners/SingPassSuccessfulLoginListenerTest.php b/tests/Unit/Listeners/SingPassSuccessfulLoginListenerTest.php
index c04c96f..f55dd09 100644
--- a/tests/Unit/Listeners/SingPassSuccessfulLoginListenerTest.php
+++ b/tests/Unit/Listeners/SingPassSuccessfulLoginListenerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Listeners;
 
 use Accredifysg\SingPassLogin\Events\SingPassSuccessfulLoginEvent;
diff --git a/tests/Unit/Models/CorpPassUserTest.php b/tests/Unit/Models/CorpPassUserTest.php
index 4640b14..4fb8070 100644
--- a/tests/Unit/Models/CorpPassUserTest.php
+++ b/tests/Unit/Models/CorpPassUserTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Models;
 
 use Accredifysg\SingPassLogin\Exceptions\JwtPayloadException;
diff --git a/tests/Unit/Services/CodeChallengeVerifierServiceTest.php b/tests/Unit/Services/CodeChallengeVerifierServiceTest.php
index 6500a2e..58e25bc 100644
--- a/tests/Unit/Services/CodeChallengeVerifierServiceTest.php
+++ b/tests/Unit/Services/CodeChallengeVerifierServiceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services;
 
 use Accredifysg\SingPassLogin\Services\CodeChallengeVerifierService;
diff --git a/tests/Unit/Services/DPoPServiceTest.php b/tests/Unit/Services/DPoPServiceTest.php
index 94f5aa9..fd5cf43 100644
--- a/tests/Unit/Services/DPoPServiceTest.php
+++ b/tests/Unit/Services/DPoPServiceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services;
 
 use Accredifysg\SingPassLogin\Services\DPoPService;
diff --git a/tests/Unit/Services/FapiAuthenticationServiceTest.php b/tests/Unit/Services/FapiAuthenticationServiceTest.php
index a34c3d9..ddf098f 100644
--- a/tests/Unit/Services/FapiAuthenticationServiceTest.php
+++ b/tests/Unit/Services/FapiAuthenticationServiceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services;
 
 use Accredifysg\SingPassLogin\DTOs\OpenIdConfigurationDto;
diff --git a/tests/Unit/Services/FapiCallbackServiceTest.php b/tests/Unit/Services/FapiCallbackServiceTest.php
index 5e869b2..7e7b848 100644
--- a/tests/Unit/Services/FapiCallbackServiceTest.php
+++ b/tests/Unit/Services/FapiCallbackServiceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services;
 
 use Accredifysg\SingPassLogin\DTOs\FapiCallbackResult;
diff --git a/tests/Unit/Services/GetUserInfoServiceTest.php b/tests/Unit/Services/GetUserInfoServiceTest.php
index 2197e24..7217ecb 100644
--- a/tests/Unit/Services/GetUserInfoServiceTest.php
+++ b/tests/Unit/Services/GetUserInfoServiceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services;
 
 use Accredifysg\SingPassLogin\DTOs\OpenIdConfigurationDto;
diff --git a/tests/Unit/Services/JwksServiceTest.php b/tests/Unit/Services/JwksServiceTest.php
index fb66b5c..65a83db 100644
--- a/tests/Unit/Services/JwksServiceTest.php
+++ b/tests/Unit/Services/JwksServiceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services;
 
 use Accredifysg\SingPassLogin\DTOs\OpenIdConfigurationDto;
diff --git a/tests/Unit/Services/OpenIdDiscoveryServiceTest.php b/tests/Unit/Services/OpenIdDiscoveryServiceTest.php
index 5a23023..5801084 100644
--- a/tests/Unit/Services/OpenIdDiscoveryServiceTest.php
+++ b/tests/Unit/Services/OpenIdDiscoveryServiceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services;
 
 use Accredifysg\SingPassLogin\DTOs\OpenIdConfigurationDto;
diff --git a/tests/Unit/Services/PushedAuthorizationRequestServiceTest.php b/tests/Unit/Services/PushedAuthorizationRequestServiceTest.php
index 4039fa9..0010850 100644
--- a/tests/Unit/Services/PushedAuthorizationRequestServiceTest.php
+++ b/tests/Unit/Services/PushedAuthorizationRequestServiceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services;
 
 use Accredifysg\SingPassLogin\DTOs\OpenIdConfigurationDto;
diff --git a/tests/Unit/Services/ScopeValidationServiceTest.php b/tests/Unit/Services/ScopeValidationServiceTest.php
index ff2a33c..4285e5f 100644
--- a/tests/Unit/Services/ScopeValidationServiceTest.php
+++ b/tests/Unit/Services/ScopeValidationServiceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services;
 
 use Accredifysg\SingPassLogin\Services\ScopeValidationService;
diff --git a/tests/Unit/Services/SingPassJwtService/GenerateClientAssertionTest.php b/tests/Unit/Services/SingPassJwtService/GenerateClientAssertionTest.php
index d176ede..4a5ca36 100644
--- a/tests/Unit/Services/SingPassJwtService/GenerateClientAssertionTest.php
+++ b/tests/Unit/Services/SingPassJwtService/GenerateClientAssertionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services\SingPassJwtService;
 
 use Accredifysg\SingPassLogin\Exceptions\JwksInvalidException;
diff --git a/tests/Unit/Services/SingPassJwtService/GetSigningJwkTest.php b/tests/Unit/Services/SingPassJwtService/GetSigningJwkTest.php
index 42d8909..17c7c05 100644
--- a/tests/Unit/Services/SingPassJwtService/GetSigningJwkTest.php
+++ b/tests/Unit/Services/SingPassJwtService/GetSigningJwkTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services\SingPassJwtService;
 
 use Accredifysg\SingPassLogin\Exceptions\JwksInvalidException;
diff --git a/tests/Unit/Services/SingPassJwtService/JweDecryptTest.php b/tests/Unit/Services/SingPassJwtService/JweDecryptTest.php
index f9744f5..4d37384 100644
--- a/tests/Unit/Services/SingPassJwtService/JweDecryptTest.php
+++ b/tests/Unit/Services/SingPassJwtService/JweDecryptTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services\SingPassJwtService;
 
 use Accredifysg\SingPassLogin\Exceptions\JweDecryptionFailedException;
diff --git a/tests/Unit/Services/SingPassJwtService/JwtDecodeTest.php b/tests/Unit/Services/SingPassJwtService/JwtDecodeTest.php
index 4639d36..afdf64a 100644
--- a/tests/Unit/Services/SingPassJwtService/JwtDecodeTest.php
+++ b/tests/Unit/Services/SingPassJwtService/JwtDecodeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services\SingPassJwtService;
 
 use Accredifysg\SingPassLogin\Exceptions\JwtDecodeFailedException;
diff --git a/tests/Unit/Services/SingPassJwtService/VerifyPayloadTest.php b/tests/Unit/Services/SingPassJwtService/VerifyPayloadTest.php
index b5fb048..e308709 100644
--- a/tests/Unit/Services/SingPassJwtService/VerifyPayloadTest.php
+++ b/tests/Unit/Services/SingPassJwtService/VerifyPayloadTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services\SingPassJwtService;
 
 use Accredifysg\SingPassLogin\Exceptions\JwtPayloadException;
diff --git a/tests/Unit/Services/TokenExchangeServiceTest.php b/tests/Unit/Services/TokenExchangeServiceTest.php
index ec5cfcf..c76036b 100644
--- a/tests/Unit/Services/TokenExchangeServiceTest.php
+++ b/tests/Unit/Services/TokenExchangeServiceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit\Services;
 
 use Accredifysg\SingPassLogin\DTOs\OpenIdConfigurationDto;
diff --git a/tests/Unit/SingPassLoginServiceProviderTest.php b/tests/Unit/SingPassLoginServiceProviderTest.php
index de2a68c..ba1f6c4 100644
--- a/tests/Unit/SingPassLoginServiceProviderTest.php
+++ b/tests/Unit/SingPassLoginServiceProviderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Accredifysg\SingPassLogin\Tests\Unit;
 
 use Accredifysg\SingPassLogin\Events\SingPassSuccessfulLoginEvent;