Add form request validation tests for various client and admin requests

tests/Feature/Requests/Client/PaymentRequestTest.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace Tests\Feature\Requests\Client;
+
+use App\Http\Requests\Client\PaymentRequest;
+use App\Models\Invoice;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Tests\Concerns\ValidatesFormRequests;
+use Tests\TestCase;
+
+class PaymentRequestTest extends TestCase
+{
+    use RefreshDatabase, ValidatesFormRequests;
+
+    public function test_passes_with_existing_invoice_id(): void
+    {
+        $invoice = Invoice::factory()->create();
+
+        $this->assertPasses(PaymentRequest::class, ['invoice_id' => $invoice->id]);
+    }
+
+    public function test_fails_without_invoice_id(): void
+    {
+        $this->assertFailsOn('invoice_id', PaymentRequest::class, []);
+    }
+
+    public function test_fails_with_non_integer_invoice_id(): void
+    {
+        $this->assertFailsOn('invoice_id', PaymentRequest::class, ['invoice_id' => 'abc']);
+    }
+
+    public function test_fails_with_unknown_invoice_id(): void
+    {
+        $this->assertFailsOn('invoice_id', PaymentRequest::class, ['invoice_id' => 999]);
+    }
+}