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/TestCase.php

@@ -0,0 +1,75 @@
+<?php
+/**
+ * Base Test Case
+ *
+ * @package Magdev\WcComposableProduct\Tests
+ */
+
+namespace Magdev\WcComposableProduct\Tests;
+
+use PHPUnit\Framework\TestCase as PHPUnitTestCase;
+use Mockery\Adapter\Phpunit\MockeryPHPUnitIntegration;
+use Brain\Monkey;
+
+/**
+ * Base test case with Brain Monkey and Mockery integration.
+ *
+ * All test classes should extend this instead of PHPUnit\Framework\TestCase.
+ */
+abstract class TestCase extends PHPUnitTestCase
+{
+    use MockeryPHPUnitIntegration;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        Monkey\setUp();
+
+        // Stub common WordPress translation functions (__(), _e(), esc_html__(), etc.)
+        Monkey\Functions\stubTranslationFunctions();
+
+        // Stub common WordPress escaping functions (esc_html(), esc_attr(), etc.)
+        Monkey\Functions\stubEscapeFunctions();
+    }
+
+    protected function tearDown(): void
+    {
+        Monkey\tearDown();
+        parent::tearDown();
+    }
+
+    /**
+     * Create a Mockery mock of WC_Product with sensible defaults.
+     *
+     * @param array $overrides Method return value overrides
+     * @return \Mockery\MockInterface
+     */
+    protected function createProductMock(array $overrides = []): \Mockery\MockInterface
+    {
+        $defaults = [
+            'get_id' => 100,
+            'get_name' => 'Test Product',
+            'get_type' => 'simple',
+            'get_price' => '10.00',
+            'get_regular_price' => '10.00',
+            'get_price_html' => '<span>$10.00</span>',
+            'get_permalink' => 'https://example.com/product/test',
+            'get_image_id' => 1,
+            'get_stock_quantity' => null,
+            'get_stock_status' => 'instock',
+            'is_purchasable' => true,
+            'is_in_stock' => true,
+            'managing_stock' => false,
+            'backorders_allowed' => false,
+        ];
+
+        $config = array_merge($defaults, $overrides);
+        $mock = \Mockery::mock('WC_Product');
+
+        foreach ($config as $method => $return) {
+            $mock->shouldReceive($method)->andReturn($return)->byDefault();
+        }
+
+        return $mock;
+    }
+}

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

@@ -0,0 +1,84 @@
+<?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();
+    }
+}

tests/Unit/CartHandlerTest.php

@@ -0,0 +1,184 @@
+<?php
+/**
+ * CartHandler Tests
+ *
+ * @package Magdev\WcComposableProduct\Tests
+ */
+
+namespace Magdev\WcComposableProduct\Tests\Unit;
+
+use Magdev\WcComposableProduct\Tests\TestCase;
+use Magdev\WcComposableProduct\CartHandler;
+use Brain\Monkey\Functions;
+use Brain\Monkey\Actions;
+use Brain\Monkey\Filters;
+
+class CartHandlerTest extends TestCase
+{
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        // Clean up POST superglobal between tests
+        $_POST = [];
+    }
+
+    protected function tearDown(): void
+    {
+        $_POST = [];
+        parent::tearDown();
+    }
+
+    public function testConstructor_RegistersExpectedHooks(): void
+    {
+        $handler = new CartHandler();
+
+        self::assertNotFalse(has_filter('woocommerce_add_to_cart_validation', 'Magdev\WcComposableProduct\CartHandler->validate_add_to_cart()'));
+        self::assertNotFalse(has_filter('woocommerce_add_cart_item_data', 'Magdev\WcComposableProduct\CartHandler->add_cart_item_data()'));
+        self::assertNotFalse(has_filter('woocommerce_get_cart_item_from_session', 'Magdev\WcComposableProduct\CartHandler->get_cart_item_from_session()'));
+        self::assertNotFalse(has_filter('woocommerce_get_item_data', 'Magdev\WcComposableProduct\CartHandler->display_cart_item_data()'));
+        self::assertNotFalse(has_action('woocommerce_before_calculate_totals', 'Magdev\WcComposableProduct\CartHandler->calculate_cart_item_price()'));
+        self::assertNotFalse(has_action('woocommerce_single_product_summary', 'Magdev\WcComposableProduct\CartHandler->render_product_selector()'));
+        self::assertNotFalse(has_filter('woocommerce_is_purchasable', 'Magdev\WcComposableProduct\CartHandler->hide_default_add_to_cart()'));
+    }
+
+    public function testHideDefaultAddToCart_ReturnsFalseForComposable(): void
+    {
+        $handler = new CartHandler();
+        $product = $this->createProductMock(['get_type' => 'composable']);
+
+        $result = $handler->hide_default_add_to_cart(true, $product);
+        $this->assertFalse($result);
+    }
+
+    public function testHideDefaultAddToCart_PassesThroughForSimple(): void
+    {
+        $handler = new CartHandler();
+        $product = $this->createProductMock(['get_type' => 'simple']);
+
+        $result = $handler->hide_default_add_to_cart(true, $product);
+        $this->assertTrue($result);
+    }
+
+    public function testValidateAddToCart_PassesThroughForNonComposable(): void
+    {
+        $product = $this->createProductMock(['get_type' => 'simple']);
+        Functions\expect('wc_get_product')->with(1)->andReturn($product);
+
+        $handler = new CartHandler();
+        $result = $handler->validate_add_to_cart(true, 1, 1);
+
+        $this->assertTrue($result);
+    }
+
+    public function testValidateAddToCart_ReturnsFalseWhenNoProductsSelected(): void
+    {
+        $product = $this->createProductMock(['get_type' => 'composable']);
+        Functions\expect('wc_get_product')->with(1)->andReturn($product);
+        Functions\expect('wc_add_notice')->once();
+
+        $_POST['composable_products'] = [];
+
+        $handler = new CartHandler();
+        $result = $handler->validate_add_to_cart(true, 1, 1);
+
+        $this->assertFalse($result);
+    }
+
+    public function testValidateAddToCart_ReturnsFalseWhenNoPostData(): void
+    {
+        $product = $this->createProductMock(['get_type' => 'composable']);
+        Functions\expect('wc_get_product')->with(1)->andReturn($product);
+        Functions\expect('wc_add_notice')->once();
+
+        // No $_POST['composable_products'] at all
+        $handler = new CartHandler();
+        $result = $handler->validate_add_to_cart(true, 1, 1);
+
+        $this->assertFalse($result);
+    }
+
+    public function testAddCartItemData_AddsSelectionsForComposable(): void
+    {
+        $product = $this->createProductMock(['get_type' => 'composable']);
+        Functions\expect('wc_get_product')->with(1)->andReturn($product);
+        Functions\expect('absint')->andReturnUsing(function ($val) {
+            return abs((int) $val);
+        });
+
+        $_POST['composable_products'] = ['101', '102'];
+
+        $handler = new CartHandler();
+        $result = $handler->add_cart_item_data([], 1);
+
+        $this->assertArrayHasKey('composable_products', $result);
+        $this->assertSame([101, 102], $result['composable_products']);
+        $this->assertArrayHasKey('unique_key', $result);
+    }
+
+    public function testAddCartItemData_PassesThroughForNonComposable(): void
+    {
+        $product = $this->createProductMock(['get_type' => 'simple']);
+        Functions\expect('wc_get_product')->with(1)->andReturn($product);
+
+        $handler = new CartHandler();
+        $result = $handler->add_cart_item_data(['existing' => 'data'], 1);
+
+        $this->assertSame(['existing' => 'data'], $result);
+    }
+
+    public function testGetCartItemFromSession_RestoresComposableProducts(): void
+    {
+        $handler = new CartHandler();
+        $result = $handler->get_cart_item_from_session(
+            ['data' => 'test'],
+            ['composable_products' => [101, 102]]
+        );
+
+        $this->assertSame([101, 102], $result['composable_products']);
+    }
+
+    public function testGetCartItemFromSession_PassesThroughWithoutComposableData(): void
+    {
+        $handler = new CartHandler();
+        $result = $handler->get_cart_item_from_session(
+            ['data' => 'test'],
+            []
+        );
+
+        $this->assertArrayNotHasKey('composable_products', $result);
+    }
+
+    public function testDisplayCartItemData_FormatsProductNames(): void
+    {
+        $mock1 = $this->createProductMock(['get_name' => 'Product A']);
+        $mock2 = $this->createProductMock(['get_name' => 'Product B']);
+
+        Functions\expect('wc_get_product')
+            ->andReturnUsing(function ($id) use ($mock1, $mock2) {
+                return match ($id) {
+                    101 => $mock1,
+                    102 => $mock2,
+                    default => false,
+                };
+            });
+
+        $handler = new CartHandler();
+        $result = $handler->display_cart_item_data(
+            [],
+            ['composable_products' => [101, 102]]
+        );
+
+        $this->assertCount(1, $result);
+        $this->assertStringContainsString('Product A', $result[0]['value']);
+        $this->assertStringContainsString('Product B', $result[0]['value']);
+    }
+
+    public function testDisplayCartItemData_ReturnsEmptyForNonComposable(): void
+    {
+        $handler = new CartHandler();
+        $result = $handler->display_cart_item_data([], []);
+
+        $this->assertSame([], $result);
+    }
+}

tests/Unit/PluginTest.php

@@ -0,0 +1,72 @@
+<?php
+/**
+ * Plugin Tests
+ *
+ * @package Magdev\WcComposableProduct\Tests
+ */
+
+namespace Magdev\WcComposableProduct\Tests\Unit;
+
+use Magdev\WcComposableProduct\Tests\TestCase;
+use Magdev\WcComposableProduct\Plugin;
+use Brain\Monkey\Functions;
+
+class PluginTest extends TestCase
+{
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        // Reset the singleton instance between tests
+        $reflection = new \ReflectionClass(Plugin::class);
+        $property = $reflection->getProperty('instance');
+        $property->setAccessible(true);
+        $property->setValue(null, null);
+    }
+
+    public function testInstance_ReturnsSingleton(): void
+    {
+        $instance1 = Plugin::instance();
+        $instance2 = Plugin::instance();
+
+        $this->assertSame($instance1, $instance2);
+    }
+
+    public function testInstance_ReturnsPluginClass(): void
+    {
+        $instance = Plugin::instance();
+
+        $this->assertInstanceOf(Plugin::class, $instance);
+    }
+
+    public function testAddProductType_AddsComposableToTypes(): void
+    {
+        $plugin = Plugin::instance();
+        $types = $plugin->add_product_type([]);
+
+        $this->assertArrayHasKey('composable', $types);
+    }
+
+    public function testProductClass_ReturnsCustomClassForComposable(): void
+    {
+        $plugin = Plugin::instance();
+        $class = $plugin->product_class('WC_Product', 'composable');
+
+        $this->assertSame('Magdev\WcComposableProduct\ProductType', $class);
+    }
+
+    public function testProductClass_PassesThroughForOtherTypes(): void
+    {
+        $plugin = Plugin::instance();
+        $class = $plugin->product_class('WC_Product', 'simple');
+
+        $this->assertSame('WC_Product', $class);
+    }
+
+    public function testGetTwig_ReturnsTwigEnvironment(): void
+    {
+        $plugin = Plugin::instance();
+
+        $this->assertInstanceOf(\Twig\Environment::class, $plugin->get_twig());
+    }
+}

tests/Unit/ProductTypeTest.php

@@ -0,0 +1,218 @@
+<?php
+/**
+ * ProductType Tests
+ *
+ * @package Magdev\WcComposableProduct\Tests
+ */
+
+namespace Magdev\WcComposableProduct\Tests\Unit;
+
+use Magdev\WcComposableProduct\Tests\TestCase;
+use Magdev\WcComposableProduct\ProductType;
+use Brain\Monkey\Functions;
+
+class ProductTypeTest extends TestCase
+{
+    private function createProductType(array $meta = []): ProductType
+    {
+        $product = new ProductType();
+        foreach ($meta as $key => $value) {
+            $product->update_meta_data($key, $value);
+        }
+        return $product;
+    }
+
+    public function testGetType_ReturnsComposable(): void
+    {
+        $product = $this->createProductType();
+        $this->assertSame('composable', $product->get_type());
+    }
+
+    public function testIsPurchasable_ReturnsTrue(): void
+    {
+        $product = $this->createProductType();
+        $this->assertTrue($product->is_purchasable());
+    }
+
+    public function testIsSoldIndividually_ReturnsTrue(): void
+    {
+        $product = $this->createProductType();
+        $this->assertTrue($product->is_sold_individually());
+    }
+
+    public function testGetSelectionLimit_UsesProductMeta(): void
+    {
+        Functions\expect('absint')->once()->andReturnUsing(function ($val) {
+            return abs((int) $val);
+        });
+
+        $product = $this->createProductType(['_composable_selection_limit' => '3']);
+        $this->assertSame(3, $product->get_selection_limit());
+    }
+
+    public function testGetSelectionLimit_FallsBackToGlobalDefault(): void
+    {
+        Functions\expect('get_option')
+            ->once()
+            ->with('wc_composable_default_limit', 5)
+            ->andReturn(7);
+
+        Functions\expect('absint')->once()->andReturnUsing(function ($val) {
+            return abs((int) $val);
+        });
+
+        $product = $this->createProductType();
+        $this->assertSame(7, $product->get_selection_limit());
+    }
+
+    public function testGetSelectionLimit_FallsBackToHardDefault(): void
+    {
+        Functions\expect('get_option')
+            ->once()
+            ->with('wc_composable_default_limit', 5)
+            ->andReturn(5);
+
+        Functions\expect('absint')->once()->andReturnUsing(function ($val) {
+            return abs((int) $val);
+        });
+
+        $product = $this->createProductType();
+        $this->assertSame(5, $product->get_selection_limit());
+    }
+
+    public function testGetPricingMode_UsesProductMeta(): void
+    {
+        $product = $this->createProductType(['_composable_pricing_mode' => 'fixed']);
+        $this->assertSame('fixed', $product->get_pricing_mode());
+    }
+
+    public function testGetPricingMode_FallsBackToGlobalDefault(): void
+    {
+        Functions\expect('get_option')
+            ->once()
+            ->with('wc_composable_default_pricing', 'sum')
+            ->andReturn('sum');
+
+        $product = $this->createProductType();
+        $this->assertSame('sum', $product->get_pricing_mode());
+    }
+
+    public function testShouldIncludeUnpublished_PerProductYes(): void
+    {
+        $product = $this->createProductType(['_composable_include_unpublished' => 'yes']);
+        $this->assertTrue($product->should_include_unpublished());
+    }
+
+    public function testShouldIncludeUnpublished_PerProductNo(): void
+    {
+        $product = $this->createProductType(['_composable_include_unpublished' => 'no']);
+        $this->assertFalse($product->should_include_unpublished());
+    }
+
+    public function testShouldIncludeUnpublished_FallsBackToGlobalYes(): void
+    {
+        Functions\expect('get_option')
+            ->once()
+            ->with('wc_composable_include_unpublished', 'no')
+            ->andReturn('yes');
+
+        $product = $this->createProductType();
+        $this->assertTrue($product->should_include_unpublished());
+    }
+
+    public function testShouldIncludeUnpublished_FallsBackToGlobalNo(): void
+    {
+        Functions\expect('get_option')
+            ->once()
+            ->with('wc_composable_include_unpublished', 'no')
+            ->andReturn('no');
+
+        $product = $this->createProductType();
+        $this->assertFalse($product->should_include_unpublished());
+    }
+
+    public function testGetSelectionCriteria_DefaultsToCategory(): void
+    {
+        $product = $this->createProductType();
+        $criteria = $product->get_selection_criteria();
+
+        $this->assertSame('category', $criteria['type']);
+        $this->assertSame([], $criteria['categories']);
+        $this->assertSame([], $criteria['tags']);
+        $this->assertSame('', $criteria['skus']);
+    }
+
+    public function testGetSelectionCriteria_UsesProductMeta(): void
+    {
+        $product = $this->createProductType([
+            '_composable_criteria_type' => 'tag',
+            '_composable_tags' => [5, 10],
+        ]);
+        $criteria = $product->get_selection_criteria();
+
+        $this->assertSame('tag', $criteria['type']);
+        $this->assertSame([5, 10], $criteria['tags']);
+    }
+
+    public function testCalculateComposedPrice_FixedMode(): void
+    {
+        $product = $this->createProductType(['_composable_pricing_mode' => 'fixed']);
+
+        // Set regular price via the stub's data property
+        $reflection = new \ReflectionClass($product);
+        $dataProp = $reflection->getProperty('data');
+        $dataProp->setAccessible(true);
+        $data = $dataProp->getValue($product);
+        $data['regular_price'] = '25.00';
+        $dataProp->setValue($product, $data);
+
+        $price = $product->calculate_composed_price([101, 102]);
+        $this->assertSame(25.0, $price);
+    }
+
+    public function testCalculateComposedPrice_SumMode(): void
+    {
+        Functions\expect('get_option')
+            ->with('wc_composable_default_pricing', 'sum')
+            ->andReturn('sum');
+
+        $mock1 = $this->createProductMock(['get_price' => '5.00']);
+        $mock2 = $this->createProductMock(['get_price' => '7.50']);
+
+        Functions\expect('wc_get_product')
+            ->andReturnUsing(function ($id) use ($mock1, $mock2) {
+                return match ($id) {
+                    101 => $mock1,
+                    102 => $mock2,
+                    default => false,
+                };
+            });
+
+        $product = $this->createProductType();
+        $price = $product->calculate_composed_price([101, 102]);
+
+        $this->assertSame(12.5, $price);
+    }
+
+    public function testCalculateComposedPrice_SumMode_SkipsInvalidProducts(): void
+    {
+        Functions\expect('get_option')
+            ->with('wc_composable_default_pricing', 'sum')
+            ->andReturn('sum');
+
+        $mock1 = $this->createProductMock(['get_price' => '5.00']);
+
+        Functions\expect('wc_get_product')
+            ->andReturnUsing(function ($id) use ($mock1) {
+                return match ($id) {
+                    101 => $mock1,
+                    default => false,
+                };
+            });
+
+        $product = $this->createProductType();
+        $price = $product->calculate_composed_price([101, 999]);
+
+        $this->assertSame(5.0, $price);
+    }
+}

tests/Unit/StockManagerTest.php

@@ -0,0 +1,226 @@
+<?php
+/**
+ * StockManager Tests
+ *
+ * @package Magdev\WcComposableProduct\Tests
+ */
+
+namespace Magdev\WcComposableProduct\Tests\Unit;
+
+use Magdev\WcComposableProduct\Tests\TestCase;
+use Magdev\WcComposableProduct\StockManager;
+use Brain\Monkey\Functions;
+
+class StockManagerTest extends TestCase
+{
+    private StockManager $manager;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $this->manager = new StockManager();
+    }
+
+    // --- validate_stock_availability ---
+
+    public function testValidateStock_ReturnsTrueWhenAllInStock(): void
+    {
+        $mock = $this->createProductMock([
+            'managing_stock' => false,
+            'is_in_stock' => true,
+        ]);
+
+        Functions\expect('wc_get_product')->with(1)->andReturn($mock);
+        Functions\expect('wc_get_product')->with(2)->andReturn($mock);
+
+        $result = $this->manager->validate_stock_availability([1, 2]);
+        $this->assertTrue($result);
+    }
+
+    public function testValidateStock_ReturnsTrueWhenNotManagingStock(): void
+    {
+        $mock = $this->createProductMock(['managing_stock' => false]);
+
+        Functions\expect('wc_get_product')->with(1)->andReturn($mock);
+
+        $result = $this->manager->validate_stock_availability([1]);
+        $this->assertTrue($result);
+    }
+
+    public function testValidateStock_ReturnsErrorForOutOfStock(): void
+    {
+        $mock = $this->createProductMock([
+            'managing_stock' => true,
+            'is_in_stock' => false,
+            'get_name' => 'Widget',
+        ]);
+
+        Functions\expect('wc_get_product')->with(1)->andReturn($mock);
+
+        $result = $this->manager->validate_stock_availability([1]);
+        $this->assertIsString($result);
+        $this->assertStringContainsString('Widget', $result);
+    }
+
+    public function testValidateStock_ReturnsErrorForInsufficientQuantity(): void
+    {
+        $mock = $this->createProductMock([
+            'managing_stock' => true,
+            'is_in_stock' => true,
+            'get_stock_quantity' => 1,
+            'get_name' => 'Widget',
+            'backorders_allowed' => false,
+        ]);
+
+        Functions\expect('wc_get_product')->with(1)->andReturn($mock);
+
+        $result = $this->manager->validate_stock_availability([1], 5);
+        $this->assertIsString($result);
+        $this->assertStringContainsString('Widget', $result);
+    }
+
+    public function testValidateStock_PassesWhenBackordersAllowed(): void
+    {
+        // When stock_quantity is null the insufficient-stock check is skipped,
+        // and the backorders_allowed() branch is reached.
+        $mock = $this->createProductMock([
+            'managing_stock' => true,
+            'is_in_stock' => true,
+            'get_stock_quantity' => null,
+            'backorders_allowed' => true,
+        ]);
+
+        Functions\expect('wc_get_product')->with(1)->andReturn($mock);
+
+        $result = $this->manager->validate_stock_availability([1], 5);
+        $this->assertTrue($result);
+    }
+
+    public function testValidateStock_SkipsNullProducts(): void
+    {
+        Functions\expect('wc_get_product')->with(999)->andReturn(false);
+
+        $result = $this->manager->validate_stock_availability([999]);
+        $this->assertTrue($result);
+    }
+
+    // --- get_product_stock_info ---
+
+    public function testGetProductStockInfo_ReturnsCorrectStructure(): void
+    {
+        $mock = $this->createProductMock([
+            'is_in_stock' => true,
+            'get_stock_quantity' => 10,
+            'backorders_allowed' => false,
+            'get_stock_status' => 'instock',
+            'managing_stock' => true,
+        ]);
+
+        Functions\expect('wc_get_product')->with(1)->andReturn($mock);
+
+        $info = $this->manager->get_product_stock_info(1);
+
+        $this->assertTrue($info['in_stock']);
+        $this->assertSame(10, $info['stock_quantity']);
+        $this->assertFalse($info['backorders_allowed']);
+        $this->assertSame('instock', $info['stock_status']);
+        $this->assertTrue($info['managing_stock']);
+        $this->assertTrue($info['has_enough_stock']);
+    }
+
+    public function testGetProductStockInfo_ReturnsFallbackForInvalidProduct(): void
+    {
+        Functions\expect('wc_get_product')->with(999)->andReturn(false);
+
+        $info = $this->manager->get_product_stock_info(999);
+
+        $this->assertFalse($info['in_stock']);
+        $this->assertSame(0, $info['stock_quantity']);
+        $this->assertFalse($info['backorders_allowed']);
+        $this->assertSame('outofstock', $info['stock_status']);
+    }
+
+    public function testGetProductStockInfo_HasEnoughStockTrueWhenNotManaging(): void
+    {
+        $mock = $this->createProductMock([
+            'managing_stock' => false,
+            'get_stock_quantity' => null,
+        ]);
+
+        Functions\expect('wc_get_product')->with(1)->andReturn($mock);
+
+        $info = $this->manager->get_product_stock_info(1, 100);
+        $this->assertTrue($info['has_enough_stock']);
+    }
+
+    public function testGetProductStockInfo_HasEnoughStockFalseWhenInsufficient(): void
+    {
+        $mock = $this->createProductMock([
+            'managing_stock' => true,
+            'get_stock_quantity' => 2,
+        ]);
+
+        Functions\expect('wc_get_product')->with(1)->andReturn($mock);
+
+        $info = $this->manager->get_product_stock_info(1, 5);
+        $this->assertFalse($info['has_enough_stock']);
+    }
+
+    // --- prevent_composable_stock_reduction ---
+
+    public function testPreventStockReduction_ReturnsFalseForComposableItem(): void
+    {
+        $productMock = $this->createProductMock(['get_type' => 'composable']);
+
+        $itemMock = \Mockery::mock('WC_Order_Item_Product');
+        $itemMock->shouldReceive('get_product')->andReturn($productMock);
+
+        $orderMock = \Mockery::mock('WC_Order');
+        $orderMock->shouldReceive('get_items')->andReturn([$itemMock]);
+
+        $result = $this->manager->prevent_composable_stock_reduction(true, $orderMock);
+        $this->assertFalse($result);
+    }
+
+    public function testPreventStockReduction_PassesThroughForNonComposable(): void
+    {
+        $productMock = $this->createProductMock(['get_type' => 'simple']);
+
+        $itemMock = \Mockery::mock('WC_Order_Item_Product');
+        $itemMock->shouldReceive('get_product')->andReturn($productMock);
+
+        $orderMock = \Mockery::mock('WC_Order');
+        $orderMock->shouldReceive('get_items')->andReturn([$itemMock]);
+
+        $result = $this->manager->prevent_composable_stock_reduction(true, $orderMock);
+        $this->assertTrue($result);
+    }
+
+    // --- store_selected_products_in_order ---
+
+    public function testStoreSelectedProducts_AddsMetaWhenPresent(): void
+    {
+        $itemMock = \Mockery::mock('WC_Order_Item_Product');
+        $itemMock->shouldReceive('add_meta_data')
+            ->once()
+            ->with('_composable_products', [1, 2], true);
+
+        $this->manager->store_selected_products_in_order(
+            $itemMock,
+            'cart_key',
+            ['composable_products' => [1, 2]]
+        );
+    }
+
+    public function testStoreSelectedProducts_DoesNothingWithoutData(): void
+    {
+        $itemMock = \Mockery::mock('WC_Order_Item_Product');
+        $itemMock->shouldNotReceive('add_meta_data');
+
+        $this->manager->store_selected_products_in_order(
+            $itemMock,
+            'cart_key',
+            []
+        );
+    }
+}

tests/bootstrap.php

@@ -0,0 +1,33 @@
+<?php
+/**
+ * PHPUnit Bootstrap
+ *
+ * Sets up WooCommerce stubs, plugin constants, and the Composer autoloader
+ * for running unit tests without a full WordPress installation.
+ *
+ * @package Magdev\WcComposableProduct\Tests
+ */
+
+// Composer autoloader (loads Brain Monkey, Mockery, plugin classes)
+require_once dirname(__DIR__) . '/vendor/autoload.php';
+
+// Define WordPress constants that the plugin expects
+defined('ABSPATH') || define('ABSPATH', '/tmp/wordpress/');
+defined('WP_DEBUG') || define('WP_DEBUG', true);
+defined('DOING_AJAX') || define('DOING_AJAX', false);
+
+// Define plugin constants
+defined('WC_COMPOSABLE_PRODUCT_VERSION') || define('WC_COMPOSABLE_PRODUCT_VERSION', '1.3.1');
+defined('WC_COMPOSABLE_PRODUCT_FILE') || define('WC_COMPOSABLE_PRODUCT_FILE', dirname(__DIR__) . '/wc-composable-product.php');
+defined('WC_COMPOSABLE_PRODUCT_PATH') || define('WC_COMPOSABLE_PRODUCT_PATH', dirname(__DIR__) . '/');
+defined('WC_COMPOSABLE_PRODUCT_URL') || define('WC_COMPOSABLE_PRODUCT_URL', 'https://example.com/wp-content/plugins/wc-composable-product/');
+defined('WC_COMPOSABLE_PRODUCT_BASENAME') || define('WC_COMPOSABLE_PRODUCT_BASENAME', 'wc-composable-product/wc-composable-product.php');
+
+// Load WooCommerce class stubs (parent before child)
+require_once __DIR__ . '/stubs/class-wc-data.php';
+require_once __DIR__ . '/stubs/class-wc-product.php';
+require_once __DIR__ . '/stubs/class-wc-settings-page.php';
+require_once __DIR__ . '/stubs/class-wc-order.php';
+require_once __DIR__ . '/stubs/class-wc-order-item-product.php';
+require_once __DIR__ . '/stubs/class-wc-cart.php';
+require_once __DIR__ . '/stubs/class-wc-admin-settings.php';

tests/stubs/class-wc-admin-settings.php

@@ -0,0 +1,11 @@
+<?php
+/**
+ * Minimal WC_Admin_Settings stub for unit testing.
+ */
+class WC_Admin_Settings {
+    public static function output_fields($options) {
+    }
+
+    public static function save_fields($options) {
+    }
+}

tests/stubs/class-wc-cart.php

@@ -0,0 +1,15 @@
+<?php
+/**
+ * Minimal WC_Cart stub for unit testing.
+ */
+class WC_Cart {
+    protected $cart_contents = [];
+
+    public function get_cart() {
+        return $this->cart_contents;
+    }
+
+    public function set_cart_contents($contents) {
+        $this->cart_contents = $contents;
+    }
+}

tests/stubs/class-wc-data.php

@@ -0,0 +1,35 @@
+<?php
+/**
+ * Minimal WC_Data stub for unit testing.
+ */
+class WC_Data {
+    protected $id = 0;
+    protected $data = [];
+    protected $meta_data = [];
+
+    public function __construct($id = 0) {
+        if (is_numeric($id) && $id > 0) {
+            $this->id = (int) $id;
+        }
+    }
+
+    public function get_id() {
+        return $this->id;
+    }
+
+    public function set_id($id) {
+        $this->id = (int) $id;
+    }
+
+    public function get_meta($key, $single = true, $context = 'view') {
+        return $this->meta_data[$key] ?? ($single ? '' : []);
+    }
+
+    public function update_meta_data($key, $value, $meta_id = 0) {
+        $this->meta_data[$key] = $value;
+    }
+
+    public function save() {
+        return $this->get_id();
+    }
+}

tests/stubs/class-wc-order-item-product.php

@@ -0,0 +1,28 @@
+<?php
+/**
+ * Minimal WC_Order_Item_Product stub for unit testing.
+ */
+class WC_Order_Item_Product extends WC_Data {
+    protected $product = null;
+    protected $quantity = 1;
+
+    public function get_product() {
+        return $this->product;
+    }
+
+    public function set_product($product) {
+        $this->product = $product;
+    }
+
+    public function get_quantity() {
+        return $this->quantity;
+    }
+
+    public function set_quantity($quantity) {
+        $this->quantity = $quantity;
+    }
+
+    public function add_meta_data($key, $value, $unique = false) {
+        $this->meta_data[$key] = $value;
+    }
+}

tests/stubs/class-wc-order.php

@@ -0,0 +1,24 @@
+<?php
+/**
+ * Minimal WC_Order stub for unit testing.
+ */
+class WC_Order extends WC_Data {
+    protected $items = [];
+    protected $order_notes = [];
+
+    public function get_items($type = '') {
+        return $this->items;
+    }
+
+    public function set_items($items) {
+        $this->items = $items;
+    }
+
+    public function add_order_note($note) {
+        $this->order_notes[] = $note;
+    }
+
+    public function get_order_notes() {
+        return $this->order_notes;
+    }
+}

tests/stubs/class-wc-product.php

@@ -0,0 +1,88 @@
+<?php
+/**
+ * Minimal WC_Product stub for unit testing.
+ */
+class WC_Product extends WC_Data {
+    protected $supports = [];
+    protected $data = [
+        'name' => '',
+        'price' => '',
+        'regular_price' => '',
+        'status' => 'publish',
+    ];
+
+    public function get_type() {
+        return 'simple';
+    }
+
+    public function get_name($context = 'view') {
+        return $this->data['name'] ?? '';
+    }
+
+    public function get_price($context = 'view') {
+        return $this->data['price'] ?? '';
+    }
+
+    public function get_regular_price($context = 'view') {
+        return $this->data['regular_price'] ?? '';
+    }
+
+    public function get_price_html() {
+        return '';
+    }
+
+    public function get_permalink() {
+        return '';
+    }
+
+    public function get_image_id($context = 'view') {
+        return 0;
+    }
+
+    public function get_stock_quantity($context = 'view') {
+        return null;
+    }
+
+    public function get_stock_status($context = 'view') {
+        return 'instock';
+    }
+
+    public function get_children() {
+        return [];
+    }
+
+    public function is_type($type) {
+        return $this->get_type() === $type;
+    }
+
+    public function is_purchasable() {
+        return true;
+    }
+
+    public function is_in_stock() {
+        return true;
+    }
+
+    public function managing_stock() {
+        return false;
+    }
+
+    public function backorders_allowed() {
+        return false;
+    }
+
+    public function is_sold_individually() {
+        return false;
+    }
+
+    public function set_price($price) {
+        $this->data['price'] = $price;
+    }
+
+    public function set_stock_quantity($quantity) {
+    }
+
+    public function supports($feature) {
+        return in_array($feature, $this->supports, true);
+    }
+}

tests/stubs/class-wc-settings-page.php

@@ -0,0 +1,29 @@
+<?php
+/**
+ * Minimal WC_Settings_Page stub for unit testing.
+ */
+class WC_Settings_Page {
+    protected $id = '';
+    protected $label = '';
+
+    public function __construct() {
+    }
+
+    public function get_id() {
+        return $this->id;
+    }
+
+    public function get_label() {
+        return $this->label;
+    }
+
+    public function get_settings() {
+        return [];
+    }
+
+    public function output() {
+    }
+
+    public function save() {
+    }
+}