Add unit tests

tests/Unit/Product/Attributes/GtinMappingTest.php

@@ -0,0 +1,123 @@
+<?php
+declare( strict_types=1 );
+
+namespace Automattic\WooCommerce\GoogleListingsAndAds\Tests\Unit\Product\Attributes;
+
+use Automattic\WooCommerce\GoogleListingsAndAds\Product\WCProductAdapter;
+use PHPUnit\Framework\TestCase;
+use WC_Helper_Product;
+
+/**
+ * Class GtinMappingTest
+ *
+ * Unit tests to confirm that the GTIN value is mapped correctly.
+ * The value should be prioritised in the following order:
+ * 
+ * 1. WooCommerce Core:       Global Unique ID
+ * 2. Google for WooCommerce: GTIN attribute
+ * 3. Google for WooCommerce: Attribute mapping rules
+ */
+class GtinMappingTest extends TestCase {
+
+    /** @var string $core_gtin Mock value to be used as the core gtin field. */
+    private $core_gtin = '219837492834';
+
+    /** @var string $gla_gtin Mock value to be used as the Google for WooCommerce gtin field. */
+    private $gla_gtin = 'gla-gtin-field';
+
+    /** @var string $gla_attribute_mapping_gtin Mock value to be used as the Google for WooCommerce attribute mapping gtin value. */
+    private $gla_attribute_mapping_gtin = 'gla-attribute-mapping-gtin';
+
+	/**
+	 * Test GTIN mapping from WooCommerce Core Global Unique ID.
+     *
+     * @return void
+	 */
+	public function test_gtin_populated_from_wc_core_global_unique_id() {
+        $mock_product = WC_Helper_Product::create_simple_product( false );
+        $mock_product->set_global_unique_id( $this->core_gtin );
+
+		$adapter = new WCProductAdapter();
+		$adapter->mapTypes( [
+			'wc_product'     => $mock_product,
+			'targetCountry'  => 'US',
+            'gla_attributes' => [
+                'gtin' => $this->gla_gtin
+            ],
+		] );
+
+		$this->assertEquals( $this->core_gtin, $adapter->getGtin() );
+	}
+
+	/**
+	 * Test GTIN mapping from Google for WooCommerce GTIN attribute.
+     *
+     * @return void
+	 */
+	public function test_gtin_populated_from_gla_gtin_attribute() {
+        $mock_product = WC_Helper_Product::create_simple_product( false );
+        $mock_product->set_sku( $this->gla_attribute_mapping_gtin );
+
+		$adapter = new WCProductAdapter();
+		$adapter->mapTypes( [
+			'wc_product'     => $mock_product,
+			'targetCountry'  => 'US',
+            'mapping_rules'  => [
+                [
+                    'attribute'               => 'gtin',
+                    'source'                  => 'product:sku',
+                    'category_condition_type' => 'all',
+                    'categories'              => ''
+                ]
+            ],
+            'gla_attributes' => [
+                'gtin' => $this->gla_gtin
+            ],
+		] );
+
+		$this->assertEquals( $this->gla_gtin, $adapter->getGtin() );
+	}
+
+	/**
+	 * Test GTIN mapping from Google for WooCommerce attribute mapping rules.
+     *
+     * @return void
+	 */
+	public function test_gtin_populated_from_attribute_mapping_rules() {
+        $mock_product = WC_Helper_Product::create_simple_product( false );
+        $mock_product->set_sku( $this->gla_attribute_mapping_gtin );
+
+		$adapter = new WCProductAdapter();
+		$adapter->mapTypes( [
+            'wc_product'    => $mock_product,
+            'targetCountry' => 'US',
+            'mapping_rules' => [
+                [
+                    'attribute'               => 'gtin',
+                    'source'                  => 'product:sku',
+                    'category_condition_type' => 'all',
+                    'categories'              => ''
+                ]
+            ],
+        ] );
+
+		$this->assertEquals( $this->gla_attribute_mapping_gtin, $adapter->getGtin() );
+	}
+
+	/**
+	 * Test GTIN remains empty when no data is available.
+     *
+     * @return void
+	 */
+	public function test_gtin_remains_empty_when_no_data_available() {
+		$mock_product = WC_Helper_Product::create_simple_product( false );
+
+		$adapter = new WCProductAdapter();
+		$adapter->mapTypes( [
+            'wc_product'    => $mock_product,
+            'targetCountry' => 'US',
+        ] );
+
+		$this->assertEquals( '', $adapter->getGtin() );
+	}
+}