Refactor the City and its tests.

app/Http/Controllers/API/v2/CartController.php

@@ -120,7 +120,7 @@ class CartController extends Controller
             return response()->json($validation);
 
         // check for not valid city
-        $validation = City::validate_with_name($cityName);
+        $validation = City::validateWithName($cityName);
         if(array_key_exists('error', $validation))
             return response()->json($validation);
 

app/Models/City.php

@@ -42,7 +42,7 @@ class City extends Model
         $this->companies()->sync($companyIDs);
     }
 
-    public function removeCompanyID(int $company_id)
+    public function removeCompanyId(int $company_id)
     {
         $this->companies()->detach($company_id);
     }
@@ -52,7 +52,7 @@ class City extends Model
         $this->companies()->detach($company_ids);
     }
 
-    public static function validate_with_name(string $name)
+    public static function validateWithName(string $name)
     {
         $name = $name ?? '';
 

tests/Feature/Validation/CityValidationTest.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace Tests\Feature;
+
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Foundation\Testing\WithFaker;
+use Tests\TestCase;
+
+use App\Models\City;
+
+class CityValidationTest extends TestCase
+{
+    public function testCityWithEmptyName(): void
+    {
+        $json = City::validateWithName('');
+
+        $this->assertEquals($json['error'], 'The city name is empty, please, write the name!!!');
+    }
+
+    public function testNotExistingCityWithName(): void
+    {
+        $name = '404 City';
+
+        $json = City::validateWithName($name);
+
+        $this->assertEquals($json['error'], 'A city with the name does not exist!!!');
+    }
+
+    public function testValidCityWithName(): void
+    {
+        $name = 'testCity';
+
+        $json = City::validateWithName($name);
+
+        $this->assertEquals($json['ok'], 'A city with the name is valid.');
+    }
+}