feat: add comprehensive tests for Medium, OtpCode, Shift models and various Enums

tests/Feature/Models/OtpCodeTest.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace Tests\Feature\Models;
+
+use App\Models\OtpCode;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Support\Carbon;
+use Tests\TestCase;
+
+class OtpCodeTest extends TestCase
+{
+    use RefreshDatabase;
+
+    public function test_is_expired_is_false_before_expiry(): void
+    {
+        $this->assertFalse(OtpCode::factory()->create()->isExpired());
+    }
+
+    public function test_is_expired_is_true_after_expiry(): void
+    {
+        $this->assertTrue(OtpCode::factory()->expired()->create()->isExpired());
+    }
+
+    public function test_is_expired_is_false_at_exact_expiry_moment(): void
+    {
+        Carbon::setTestNow('2026-09-21 10:00:00');
+        $otp = OtpCode::factory()->create(['expires_at' => now()]);
+
+        $this->assertFalse($otp->isExpired());
+    }
+}