diff --git a/.idea/php.xml b/.idea/php.xml
index d547306..69a5912 100644
--- a/.idea/php.xml
+++ b/.idea/php.xml
@@ -179,6 +179,7 @@
       <path value="$PROJECT_DIR$/vendor/mtdowling/jmespath.php" />
       <path value="$PROJECT_DIR$/vendor/psr/http-client" />
       <path value="$PROJECT_DIR$/vendor/twig/extra-bundle" />
+      <path value="$PROJECT_DIR$/vendor/staabm/side-effects-detector" />
     </include_path>
   </component>
   <component name="PhpProjectSharedConfiguration" php_language_level="8.2" />
diff --git a/tests/Service/EmailServiceTest.php b/tests/Service/EmailServiceTest.php
new file mode 100644
index 0000000..64a8971
--- /dev/null
+++ b/tests/Service/EmailServiceTest.php
@@ -0,0 +1,225 @@
+<?php
+
+namespace App\Tests\Service;
+
+use App\Entity\Organizations;
+use App\Entity\User;
+use App\Service\EmailService;
+use App\Service\LoggerService;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+use Psr\Log\LoggerInterface;
+use Symfony\Bridge\Twig\Mime\TemplatedEmail;
+use Symfony\Component\Mailer\Exception\TransportException;
+use Symfony\Component\Mailer\MailerInterface;
+use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
+
+class EmailServiceTest extends TestCase
+{
+    private EmailService $service;
+
+    // Mocks
+    private MockObject|MailerInterface $mailer;
+    private MockObject|LoggerInterface $logger; // PSR Logger
+    private MockObject|UrlGeneratorInterface $urlGenerator;
+    private MockObject|LoggerService $loggerService; // Custom Business Logger
+
+    protected function setUp(): void
+    {
+        $this->mailer = $this->createMock(MailerInterface::class);
+        $this->logger = $this->createMock(LoggerInterface::class);
+        $this->urlGenerator = $this->createMock(UrlGeneratorInterface::class);
+        $this->loggerService = $this->createMock(LoggerService::class);
+
+        $this->service = new EmailService(
+            $this->mailer,
+            $this->logger,
+            $this->urlGenerator,
+            $this->loggerService
+        );
+    }
+
+    /**
+     * Helper to set private ID property on entities.
+     */
+    private function setEntityId(object $entity, int $id): void
+    {
+        $reflection = new \ReflectionClass($entity);
+        if ($reflection->hasProperty('id')) {
+            $property = $reflection->getProperty('id');
+            // $property->setAccessible(true); // Uncomment for PHP < 8.1
+            $property->setValue($entity, $id);
+        }
+    }
+
+    // ==========================================
+    // TEST: sendPasswordSetupEmail
+    // ==========================================
+
+    public function testSendPasswordSetupEmailSuccess(): void
+    {
+        // 1. Setup Data
+        $user = new User();
+        $this->setEntityId($user, 10);
+        $user->setEmail('new@user.com');
+
+        // Token format: "o{OrgId}@{RandomHex}"
+        // We use "o50@abcdef" to test that Org ID 50 is correctly extracted
+        $token = 'o50@abcdef123456';
+
+        // 2. Expect URL Generation
+        $this->urlGenerator->expects($this->once())
+            ->method('generate')
+            ->with(
+                'password_setup',
+                ['id' => 10, 'token' => $token],
+                UrlGeneratorInterface::ABSOLUTE_URL
+            )
+            ->willReturn('https://sudalys.fr/setup/10/token');
+
+        // 3. Expect Mailer Send
+        $this->mailer->expects($this->once())
+            ->method('send')
+            ->with($this->callback(function (TemplatedEmail $email) use ($user, $token) {
+                // Verify Email Construction
+                $context = $email->getContext();
+
+                return $email->getTo()[0]->getAddress() === 'new@user.com'
+                    && $email->getSubject() === 'Définissez votre mot de passe'
+                    && $email->getHtmlTemplate() === 'emails/password_setup.html.twig'
+                    && $context['user'] === $user
+                    && $context['token'] === $token
+                    && $context['linkUrl'] === 'https://sudalys.fr/setup/10/token';
+            }));
+
+        // 4. Expect Business Log (Success)
+        // Ensure the Org ID '50' was extracted from the token 'o50@...'
+        $this->loggerService->expects($this->once())
+            ->method('logEmailSent')
+            ->with(10, 50, 'Password setup email sent.');
+
+        // 5. Run
+        $this->service->sendPasswordSetupEmail($user, $token);
+    }
+
+    public function testSendPasswordSetupEmailWithoutOrgIdInToken(): void
+    {
+        $user = new User();
+        $this->setEntityId($user, 10);
+        $user->setEmail('user@test.com');
+
+        // Token WITHOUT 'o' prefix -> Org ID should be null
+        $token = 'abcdef123456';
+
+        $this->urlGenerator->method('generate')->willReturn('https://link.com');
+
+        // Verify log receives null for Org ID
+        $this->loggerService->expects($this->once())
+            ->method('logEmailSent')
+            ->with(10, null, 'Password setup email sent.');
+
+        $this->service->sendPasswordSetupEmail($user, $token);
+    }
+
+    public function testSendPasswordSetupEmailHandlesException(): void
+    {
+        $user = new User();
+        $this->setEntityId($user, 10);
+        $user->setEmail('fail@test.com');
+        $token = 'token';
+
+        $this->urlGenerator->method('generate')->willReturn('http://link');
+
+        // Simulate Mailer Failure
+        $this->mailer->expects($this->once())
+            ->method('send')
+            ->willThrowException(new TransportException('SMTP Error'));
+
+        // Expect System Error Log
+        $this->logger->expects($this->once())
+            ->method('error')
+            ->with($this->stringContains('Failed to send password setup email: SMTP Error'));
+
+        // Ensure business log is NOT called (or called depending on where failure happens,
+        // in your code business log is AFTER mailer, so it should NOT be called)
+        $this->loggerService->expects($this->never())->method('logEmailSent');
+
+        // No exception should bubble up (caught in catch block)
+        $this->service->sendPasswordSetupEmail($user, $token);
+    }
+
+    // ==========================================
+    // TEST: sendExistingUserNotificationEmail
+    // ==========================================
+
+    public function testSendExistingUserNotificationEmailSuccess(): void
+    {
+        // 1. Setup Data
+        $user = new User();
+        $this->setEntityId($user, 20);
+        $user->setEmail('existing@user.com');
+
+        $org = new Organizations();
+        $this->setEntityId($org, 99);
+        $org->setName('My Organization');
+
+        $token = 'some-token';
+
+        // 2. Expect URL Generation
+        $this->urlGenerator->expects($this->once())
+            ->method('generate')
+            ->with(
+                'user_accept',
+                ['id' => 20, 'token' => $token],
+                UrlGeneratorInterface::ABSOLUTE_URL
+            )
+            ->willReturn('https://sudalys.fr/accept/20');
+
+        // 3. Expect Mailer Send
+        $this->mailer->expects($this->once())
+            ->method('send')
+            ->with($this->callback(function (TemplatedEmail $email) use ($org) {
+                return $email->getTo()[0]->getAddress() === 'existing@user.com'
+                    && $email->getSubject() === "Invitation à rejoindre l'organisation My Organization"
+                    && $email->getContext()['expirationDays'] === 15;
+            }));
+
+        // 4. Expect Business Log
+        $this->loggerService->expects($this->once())
+            ->method('logEmailSent')
+            ->with(20, 99, 'Existing user notification email sent.');
+
+        // 5. Run
+        $this->service->sendExistingUserNotificationEmail($user, $org, $token);
+    }
+
+    public function testSendExistingUserNotificationEmailHandlesException(): void
+    {
+        $user = new User();
+        $this->setEntityId($user, 20);
+        $user->setEmail('fail@user.com');
+
+        $org = new Organizations();
+        $this->setEntityId($org, 99);
+
+        $this->urlGenerator->method('generate')->willReturn('link');
+
+        // In this specific method, your code logs success BEFORE sending email?
+        // Looking at source:
+        // $this->loggerService->logEmailSent(...);
+        // $this->mailer->send($email);
+
+        // So we expect logEmailSent to be called even if mailer fails
+        $this->loggerService->expects($this->once())->method('logEmailSent');
+
+        $this->mailer->method('send')
+            ->willThrowException(new TransportException('Connection refused'));
+
+        // Expect System Error Log
+        $this->logger->expects($this->once())
+            ->method('error')
+            ->with($this->stringContains('Failed to send existing user notification email'));
+
+        $this->service->sendExistingUserNotificationEmail($user, $org, 'token');
+    }
+}
\ No newline at end of file