Add extensive controller and model tests

tests/Unit/RankModelTest.php

@@ -0,0 +1,22 @@
+<?php
+
+use App\Models\Rank;
+use App\Models\User;
+
+it('relates ranks to users', function (): void {
+    $rank = Rank::create([
+        'name' => 'Gold',
+        'badge_type' => 'text',
+        'badge_text' => 'G',
+        'color' => '#ffaa00',
+    ]);
+
+    $user = User::factory()->create([
+        'rank_id' => $rank->id,
+    ]);
+
+    $rank->load('users');
+
+    expect($rank->users)->toHaveCount(1);
+    expect($rank->users->first()->id)->toBe($user->id);
+});