feat: add comprehensive tests for invoice function

tests/Feature/InvoiceTest.php

@@ -0,0 +1,80 @@
+<?php
+
+namespace Tests\Feature;
+
+use Tests\TestCase;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Support\Facades\Mail;
+use App\Models\Order;
+use App\Models\Invoice;
+use App\Mail\InvoiceMail;
+
+class InvoiceTest extends TestCase
+{
+    use RefreshDatabase;
+
+    public function testAutomaticInvoiceGeneration()
+    {
+        // Arrange: Simulate order completion
+        $order = Order::factory()->create();
+
+        // Act: Trigger invoice generation
+        $response = $this->postJson('/api/orders/'.$order->id.'/complete');
+
+        // Assert: Invoice is automatically generated with correct details
+        $this->assertDatabaseHas('invoices', [
+            'order_id' => $order->id,
+        ]);
+    }
+
+    public function testInvoiceManagementInterfaceAccessibility()
+    {
+        // Act: Access the invoice management interface
+        $response = $this->get('/invoices');
+
+        // Assert: Interface is accessible
+        $response->assertStatus(200);
+    }
+
+    public function testCorrectnessOfDetailedInvoiceView()
+    {
+        // Arrange: Create an invoice
+        $invoice = Invoice::factory()->create();
+
+        // Act: View the invoice
+        $response = $this->get('/invoices/'.$invoice->id);
+
+        // Assert: Response contains correct invoice details
+        $response->assertSee($invoice->total_amount);
+    }
+
+    public function testSuccessfulPDFGeneration()
+    {
+        // Arrange: Create an invoice
+        $invoice = Invoice::factory()->create();
+
+        // Act: Request PDF generation
+        $response = $this->get('/invoices/'.$invoice->id.'/pdf');
+
+        // Assert: PDF is successfully generated
+        $response->assertHeader('Content-Type', 'application/pdf');
+    }
+
+    public function testEmailSendingWithInvoiceAttached()
+    {
+        // Arrange: Mock the mailer
+        Mail::fake();
+        $invoice = Invoice::factory()->create();
+
+        // Act: Trigger email sending
+        $this->post('/invoices/'.$invoice->id.'/send');
+
+        // Assert: Email is sent with the correct attachment
+        Mail::assertSent(InvoiceMail::class, function ($mail) use ($invoice) {
+            return $mail->hasTo($invoice->customer->email) &&
+                   $mail->attachments->contains(function ($attachment) use ($invoice) {
+                       return $attachment->as == "invoice-{$invoice->id}.pdf";
+                   });
+        });
+    }
+}