Added test for sales order

tests/DataTransferObject/SalesOrder/SalesOrderTest.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Setono\PeakWMS\DataTransferObject\SalesOrder;
+
+use PHPUnit\Framework\TestCase;
+use Setono\PeakWMS\DataTransferObject\Address;
+
+final class SalesOrderTest extends TestCase
+{
+    /**
+     * @test
+     */
+    public function it_initializes(): void
+    {
+        $now = new \DateTimeImmutable();
+
+        $salesOrder = new SalesOrder(
+            orderId: 123,
+            forwarderProductId: 'gls',
+            orderNumber: '123',
+            billingAddress: new Address(
+                customerName: 'customerName',
+                address1: 'address1',
+                postalCode: '9000',
+                city: 'city',
+                country: 'DK',
+            ),
+            orderDateTime: $now->format(\DATE_ATOM),
+            state: 3,
+        );
+
+        self::assertSame('123', $salesOrder->orderId);
+        self::assertSame('gls', $salesOrder->forwarderProductId);
+        self::assertSame('123', $salesOrder->orderNumber);
+        self::assertInstanceOf(Address::class, $salesOrder->billingAddress);
+        self::assertSame($now->format(\DATE_ATOM), $salesOrder->orderDateTime?->format(\DATE_ATOM));
+        self::assertSame(State::Packed, $salesOrder->state);
+    }
+}