diff --git a/tests/Unit/BillingPortal/DependencyTest.php b/tests/Unit/BillingPortal/DependencyTest.php
new file mode 100644
index 000000000000..2cdad70fd21a
--- /dev/null
+++ b/tests/Unit/BillingPortal/DependencyTest.php
@@ -0,0 +1,125 @@
+<?php
+
+/**
+ * Invoice Ninja (https://invoiceninja.com).
+ *
+ * @link https://github.com/invoiceninja/invoiceninja source repository
+ *
+ * @copyright Copyright (c) 2022. Invoice Ninja LLC (https://invoiceninja.com)
+ *
+ * @license https://www.elastic.co/licensing/elastic-license
+ */
+
+namespace Tests\Unit\BillingPortal;
+
+use App\Livewire\BillingPortal\Authentication\RegisterOrLogin;
+use App\Livewire\BillingPortal\Cart\Cart;
+use App\Livewire\BillingPortal\Purchase;
+use App\Livewire\BillingPortal\RFF;
+use App\Livewire\BillingPortal\Setup;
+use App\Livewire\BillingPortal\Submit;
+use Tests\TestCase;
+
+class DependencyTest extends TestCase
+{
+    protected function setUp(): void
+    {
+        parent::setUp();
+    }
+
+    public function testDependencyOrder()
+    {
+        $results = $this->checkDependencies([
+            RFF::class,
+            RegisterOrLogin::class,
+            Cart::class,
+        ]);
+
+        $this->assertCount(1, $results);
+
+        $results = $this->checkDependencies([
+            RegisterOrLogin::class,
+            Cart::class,
+            RFF::class,
+        ]);
+
+        $this->assertCount(0, $results);
+
+        $results = $this->checkDependencies([
+            RegisterOrLogin::class,
+            RFF::class,
+            Cart::class,
+        ]);
+
+        $this->assertCount(0, $results);
+    }
+
+    public function testSorting()
+    {
+        $results = $this->sort([
+            RFF::class,
+            RegisterOrLogin::class,
+            Cart::class,
+        ]);
+
+        $this->assertEquals(Purchase::$steps, $results);
+
+        $results = $this->sort([
+            RegisterOrLogin::class,
+            Cart::class,
+            RFF::class,
+        ]);
+
+        $this->assertEquals([
+            Setup::class,
+            RegisterOrLogin::class,
+            Cart::class,
+            RFF::class,
+            Submit::class,
+        ], $results);
+
+        $results = $this->sort([
+            RegisterOrLogin::class,
+            RFF::class,
+            Cart::class,
+        ]);
+
+        $this->assertEquals([
+            Setup::class,
+            RegisterOrLogin::class,
+            RFF::class,
+            Cart::class,
+            Submit::class,
+        ], $results);
+    }
+
+    private function checkDependencies(array $steps): array
+    {
+        $dependencies = Purchase::$dependencies;
+        $stepOrder = array_flip($steps);
+        $errors = [];
+
+        foreach ($steps as $step) {
+            $dependentClasses = $dependencies[$step] ?? [];
+
+            foreach ($dependentClasses as $dependency) {
+                if (in_array($dependency, $steps) && $stepOrder[$dependency] > $stepOrder[$step]) {
+                    $errors[] = "Dependency error: $step depends on $dependency";
+                }
+            }
+        }
+
+        return $errors;
+    }
+
+    private function sort(array $dependencies): array
+    {
+        $errors = $this->checkDependencies($dependencies);
+
+        if (count($errors)) {
+            return Purchase::$steps;
+        }
+
+        return [Setup::class, ...$dependencies, Submit::class];
+    }
+}