test that carrier email is unique

src/Carrier/CarrierRepository.php

@@ -5,6 +5,7 @@ namespace FreightQuote\Carrier;
 interface CarrierRepository
 {
     public function find(int $id): ?Carrier;
+    public function findByEmail(string $email): ?Carrier;
     public function save(Carrier $carrier): Carrier;
 
     /**

src/Carrier/UseCases/CreateCarrier.php

@@ -4,6 +4,7 @@ namespace FreightQuote\Carrier\UseCases;
 
 use FreightQuote\Carrier\Carrier;
 use FreightQuote\Carrier\CarrierRepository;
+use InvalidArgumentException;
 
 class CreateCarrier
 {
@@ -13,6 +14,9 @@ class CreateCarrier
 
     public function execute(CreateCarrierRequest $dto): Carrier
     {
+        if ($this->carrierRepo->findByEmail($dto->email) !== null) {
+            throw new InvalidArgumentException();
+        }
         $carrier = new Carrier(
             null,
             $dto->email,

tests/Fakes/Carrier/FakeCarrierRepository.php

@@ -73,4 +73,24 @@ class FakeCarrierRepository implements CarrierRepository
             );
         }, $this->existingCarriers);
     }
+
+    public function findByEmail(string $email): ?Carrier
+    {
+        foreach ($this->existingCarriers as $carrier) {
+            if ($carrier->getEmail() === $email) {
+                return new Carrier(
+                    $carrier->getId(),
+                    $email,
+                    $carrier->getCompanyName(),
+                    $carrier->getContactPerson(),
+                    $carrier->getPhoneNumber(),
+                    $carrier->getNotes(),
+                    $carrier->getLoadProfile(),
+                    $carrier->getCountriesServing(),
+                );
+            }
+        }
+
+        return null;
+    }
 }

tests/Unit/Carrier/UseCases/CreateCarrierTest.php

@@ -3,6 +3,7 @@
 namespace Tests\Unit\Carrier\UseCases;
 
 use PHPUnit\Framework\TestCase;
+use InvalidArgumentException;
 use Tests\Fakes\Carrier\FakeCarrierRepository;
 use FreightQuote\Carrier\UseCases\CreateCarrier;
 use FreightQuote\Carrier\UseCases\CreateCarrierRequest;
@@ -39,4 +40,38 @@ class CreateCarrierTest extends TestCase
         $this->assertEquals($loadProfile, $foundCarrier->getLoadProfile());
         $this->assertEquals($countriesServing, $foundCarrier->getCountriesServing());
     }
+
+    public function test_email_is_unique(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $email = 'joe@shmoe.com';
+        $company = 'test company';
+        $contactPerson = 'Joe Shmoe';
+        $phoneNumber = '132456798';
+        $notes = 'some notes';
+        $loadProfile = 'LTL/FTL'; // Less than full trailer load and full trailer load
+        $countriesServing = ['USA', 'FRA', 'UK'];
+        $carrierRepo = new FakeCarrierRepository();
+        $dto1 = new CreateCarrierRequest(
+            $email,
+            $company,
+            $contactPerson,
+            $phoneNumber,
+            $notes,
+            $loadProfile,
+            $countriesServing,
+        );
+        $dto2 = new CreateCarrierRequest(
+            $email,
+            $company,
+            $contactPerson,
+            $phoneNumber,
+            $notes,
+            $loadProfile,
+            $countriesServing,
+        );
+        $useCase = new CreateCarrier($carrierRepo);
+        $useCase->execute($dto1);
+        $useCase->execute($dto2);
+    }
 }