diff --git a/tests/Unit/User/UseCases/CreateUserTest.php b/tests/Unit/User/UseCases/CreateUserTest.php
index bf2c793..1a97716 100644
--- a/tests/Unit/User/UseCases/CreateUserTest.php
+++ b/tests/Unit/User/UseCases/CreateUserTest.php
@@ -58,4 +58,20 @@ class CreateUserTest extends TestCase
         $user = $userRepo->find(0);
         $this->assertTrue($user->isAdmin());
     }
+
+    public function test_throws_when_email_already_taken(): void
+    {
+        $userRepo = new FakeUserRepository();
+        $useCase = new CreateUser($userRepo);
+        $useCase->execute(new CreateUserRequest(
+            email: 'test@test.com',
+        ));
+
+        $this->expectException(BadRequestException::class);
+        $this->expectExceptionMessage('email already taken');
+
+        $useCase->execute(new CreateUserRequest(
+            email: 'test@test.com',
+        ));
+    }
 }