Add PHPUnit test suite, PSR-4 refactor, lint+test CI jobs (v1.3.1)

- 57 unit tests covering ProductType, StockManager, CartHandler, Plugin,
  Admin/ProductData, Admin/Settings using Brain Monkey + Mockery
- WooCommerce class stubs for testing without WP installation
- PHP lint and test jobs in release workflow (test gate blocks release)
- PSR-4 namespace change: WC_Composable_Product -> Magdev\WcComposableProduct
- PascalCase filenames for all classes under includes/

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/Unit/Admin/ProductDataTest.php

@@ -0,0 +1,108 @@
+<?php
+/**
+ * Admin ProductData Tests
+ *
+ * @package Magdev\WcComposableProduct\Tests
+ */
+
+namespace Magdev\WcComposableProduct\Tests\Unit\Admin;
+
+use Magdev\WcComposableProduct\Tests\TestCase;
+use Magdev\WcComposableProduct\Admin\ProductData;
+use Brain\Monkey\Functions;
+
+class ProductDataTest extends TestCase
+{
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $_POST = [];
+    }
+
+    protected function tearDown(): void
+    {
+        $_POST = [];
+        parent::tearDown();
+    }
+
+    public function testConstructor_RegistersExpectedHooks(): void
+    {
+        $productData = new ProductData();
+
+        self::assertNotFalse(has_filter('woocommerce_product_data_tabs', 'Magdev\WcComposableProduct\Admin\ProductData->add_product_data_tab()'));
+        self::assertNotFalse(has_action('woocommerce_product_data_panels', 'Magdev\WcComposableProduct\Admin\ProductData->add_product_data_panel()'));
+        self::assertNotFalse(has_action('woocommerce_process_product_meta_composable', 'Magdev\WcComposableProduct\Admin\ProductData->save_product_data()'));
+        self::assertNotFalse(has_action('woocommerce_product_options_general_product_data', 'Magdev\WcComposableProduct\Admin\ProductData->add_general_fields()'));
+    }
+
+    public function testAddProductDataTab_AddsComposableTab(): void
+    {
+        $productData = new ProductData();
+        $tabs = $productData->add_product_data_tab([]);
+
+        $this->assertArrayHasKey('composable', $tabs);
+        $this->assertSame('composable_product_data', $tabs['composable']['target']);
+        $this->assertContains('show_if_composable', $tabs['composable']['class']);
+        $this->assertSame(21, $tabs['composable']['priority']);
+    }
+
+    public function testSaveProductData_SavesAllFields(): void
+    {
+        $_POST = [
+            '_composable_selection_limit' => '5',
+            '_composable_pricing_mode' => 'fixed',
+            '_composable_include_unpublished' => 'yes',
+            '_composable_criteria_type' => 'tag',
+            '_composable_categories' => ['1', '2'],
+            '_composable_tags' => ['3', '4'],
+            '_composable_skus' => 'SKU-1, SKU-2',
+        ];
+
+        Functions\expect('absint')->andReturnUsing(function ($val) {
+            return abs((int) $val);
+        });
+        Functions\expect('sanitize_text_field')->andReturnUsing(function ($val) {
+            return $val;
+        });
+        Functions\expect('sanitize_textarea_field')->andReturnUsing(function ($val) {
+            return $val;
+        });
+
+        Functions\expect('update_post_meta')->times(7);
+
+        $productData = new ProductData();
+        $productData->save_product_data(42);
+    }
+
+    public function testSaveProductData_DefaultsWhenPostEmpty(): void
+    {
+        // No POST data at all
+        Functions\expect('absint')->andReturnUsing(function ($val) {
+            return abs((int) $val);
+        });
+        Functions\expect('sanitize_text_field')->andReturnUsing(function ($val) {
+            return $val;
+        });
+        Functions\expect('sanitize_textarea_field')->andReturnUsing(function ($val) {
+            return $val;
+        });
+
+        Functions\expect('update_post_meta')
+            ->with(42, '_composable_selection_limit', \Mockery::any())->once();
+        Functions\expect('update_post_meta')
+            ->with(42, '_composable_pricing_mode', '')->once();
+        Functions\expect('update_post_meta')
+            ->with(42, '_composable_include_unpublished', '')->once();
+        Functions\expect('update_post_meta')
+            ->with(42, '_composable_criteria_type', 'category')->once();
+        Functions\expect('update_post_meta')
+            ->with(42, '_composable_categories', [])->once();
+        Functions\expect('update_post_meta')
+            ->with(42, '_composable_tags', [])->once();
+        Functions\expect('update_post_meta')
+            ->with(42, '_composable_skus', '')->once();
+
+        $productData = new ProductData();
+        $productData->save_product_data(42);
+    }
+}

tests/Unit/Admin/SettingsTest.php

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+<?php
+/**
+ * Admin Settings Tests
+ *
+ * @package Magdev\WcComposableProduct\Tests
+ */
+
+namespace Magdev\WcComposableProduct\Tests\Unit\Admin;
+
+use Magdev\WcComposableProduct\Tests\TestCase;
+use Magdev\WcComposableProduct\Admin\Settings;
+use Brain\Monkey\Functions;
+
+class SettingsTest extends TestCase
+{
+    public function testConstructor_SetsIdAndLabel(): void
+    {
+        $settings = new Settings();
+
+        $this->assertSame('composable_products', $settings->get_id());
+    }
+
+    public function testGetSettings_ReturnsExpectedFieldIds(): void
+    {
+        Functions\expect('apply_filters')
+            ->once()
+            ->with('wc_composable_settings', \Mockery::type('array'))
+            ->andReturnUsing(function ($hook, $settings) {
+                return $settings;
+            });
+
+        $settings = new Settings();
+        $fields = $settings->get_settings();
+
+        // Extract all field IDs
+        $ids = array_column($fields, 'id');
+
+        $this->assertContains('wc_composable_settings', $ids);
+        $this->assertContains('wc_composable_default_limit', $ids);
+        $this->assertContains('wc_composable_default_pricing', $ids);
+        $this->assertContains('wc_composable_include_unpublished', $ids);
+        $this->assertContains('wc_composable_show_images', $ids);
+        $this->assertContains('wc_composable_show_prices', $ids);
+        $this->assertContains('wc_composable_show_total', $ids);
+    }
+
+    public function testGetSettings_HasCorrectFieldTypes(): void
+    {
+        Functions\expect('apply_filters')
+            ->once()
+            ->andReturnUsing(function ($hook, $settings) {
+                return $settings;
+            });
+
+        $settings = new Settings();
+        $fields = $settings->get_settings();
+
+        // Index fields by ID for easy lookup
+        $indexed = [];
+        foreach ($fields as $field) {
+            if (isset($field['id'])) {
+                $indexed[$field['id']] = $field;
+            }
+        }
+
+        $this->assertSame('number', $indexed['wc_composable_default_limit']['type']);
+        $this->assertSame('select', $indexed['wc_composable_default_pricing']['type']);
+        $this->assertSame('checkbox', $indexed['wc_composable_include_unpublished']['type']);
+        $this->assertSame('checkbox', $indexed['wc_composable_show_images']['type']);
+    }
+
+    public function testGetSettings_AppliesFilter(): void
+    {
+        Functions\expect('apply_filters')
+            ->once()
+            ->with('wc_composable_settings', \Mockery::type('array'))
+            ->andReturnUsing(function ($hook, $settings) {
+                return $settings;
+            });
+
+        $settings = new Settings();
+        $settings->get_settings();
+    }
+}