test seeded development user

backend/tests/Feature/Database/DatabaseSeederTest.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace Tests\Feature\Database;
+
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Tests\TestCase;
+
+class DatabaseSeederTest extends TestCase
+{
+    use RefreshDatabase;
+
+    public function test_it_seeds_the_development_user_idempotently(): void
+    {
+        $this->seed();
+        $this->seed();
+
+        $this->assertDatabaseHas('users', [
+            'email' => 'user@example.com',
+        ]);
+        $this->assertDatabaseCount('users', 1);
+    }
+}