Fix #25900 - image size customisation controls not shown

- Added the `ThemeSupport class`, with methods to add and get
  theme support options.
  - It also has a new `add_default_options` method that adds the
    options under a `_defaults` key.
- The `WC_Twenty_*` classes now use `ThemeSupport` instead of
  the `add_theme_support` function to define image and thumbnail sizes.
  - The values are defined as default options.
- The `WC_Shop_Customizer` class now uses `ThemeSupport` instead of
  `wc_get_theme_support` to check if image and thumbnail sizes UI
  should be rendered.
  - The check is made excluding default values.

With these changes the UI to change the image and thumbnail sizes
is hidden only if the options are added as non-defaults elsewhere.

Additional changes:

- The code of the `wc_get_theme_support` function is replaced with
  a simple call to `get_option` in `ThemeSupport`.
- Added the utility class `ArrayUtil`.

includes/customizer/class-wc-shop-customizer.php

@@ -6,6 +6,8 @@
  * @package WooCommerce
  */
 
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
+
 defined( 'ABSPATH' ) || exit;
 
 /**
@@ -13,10 +15,19 @@ defined( 'ABSPATH' ) || exit;
  */
 class WC_Shop_Customizer {
 
+	/**
+	 * Holds the instance of ThemeSupport to use.
+	 *
+	 * @var ThemeSupport $theme_support The instance of ThemeSupport to use.
+	 */
+	private $theme_support;
+
 	/**
 	 * Constructor.
 	 */
 	public function __construct() {
+		$this->theme_support = wc_get_container()->get( ThemeSupport::class );
+
 		add_action( 'customize_register', array( $this, 'add_sections' ) );
 		add_action( 'customize_controls_print_styles', array( $this, 'add_styles' ) );
 		add_action( 'customize_controls_print_scripts', array( $this, 'add_scripts' ), 30 );
@@ -545,11 +556,11 @@ class WC_Shop_Customizer {
 			)
 		);
 
-		if ( ! wc_get_theme_support( 'single_image_width' ) ) {
+		if ( ! $this->theme_support->has_option( 'single_image_width', false ) ) {
 			$wp_customize->add_setting(
 				'woocommerce_single_image_width',
 				array(
-					'default'              => 600,
+					'default'              => $this->theme_support->get_option( 'single_image_width', 600 ),
 					'type'                 => 'option',
 					'capability'           => 'manage_woocommerce',
 					'sanitize_callback'    => 'absint',
@@ -573,11 +584,11 @@ class WC_Shop_Customizer {
 			);
 		}
 
-		if ( ! wc_get_theme_support( 'thumbnail_image_width' ) ) {
+		if ( ! $this->theme_support->has_option( 'thumbnail_image_width', false ) ) {
 			$wp_customize->add_setting(
 				'woocommerce_thumbnail_image_width',
 				array(
-					'default'              => 300,
+					'default'              => $this->theme_support->get_option( 'thumbnail_image_width', 300 ),
 					'type'                 => 'option',
 					'capability'           => 'manage_woocommerce',
 					'sanitize_callback'    => 'absint',

includes/theme-support/class-wc-twenty-eleven.php

@@ -6,6 +6,8 @@
  * @package WooCommerce\Classes
  */
 
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
+
 defined( 'ABSPATH' ) || exit;
 
 /**
@@ -29,8 +31,7 @@ class WC_Twenty_Eleven {
 		add_theme_support( 'wc-product-gallery-zoom' );
 		add_theme_support( 'wc-product-gallery-lightbox' );
 		add_theme_support( 'wc-product-gallery-slider' );
-		add_theme_support(
+		wc_get_container()->get( ThemeSupport::class )->add_default_options(
-			'woocommerce',
 			array(
 				'thumbnail_image_width' => 150,
 				'single_image_width'    => 300,

includes/theme-support/class-wc-twenty-fifteen.php

@@ -7,6 +7,8 @@
  * @package WooCommerce\Classes
  */
 
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
+
 defined( 'ABSPATH' ) || exit;
 
 /**
@@ -30,8 +32,7 @@ class WC_Twenty_Fifteen {
 		add_theme_support( 'wc-product-gallery-zoom' );
 		add_theme_support( 'wc-product-gallery-lightbox' );
 		add_theme_support( 'wc-product-gallery-slider' );
-		add_theme_support(
+		wc_get_container()->get( ThemeSupport::class )->add_default_options(
-			'woocommerce',
 			array(
 				'thumbnail_image_width' => 200,
 				'single_image_width'    => 350,

includes/theme-support/class-wc-twenty-fourteen.php

@@ -7,6 +7,8 @@
  * @package WooCommerce\Classes
  */
 
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
+
 defined( 'ABSPATH' ) || exit;
 
 /**
@@ -30,8 +32,7 @@ class WC_Twenty_Fourteen {
 		add_theme_support( 'wc-product-gallery-zoom' );
 		add_theme_support( 'wc-product-gallery-lightbox' );
 		add_theme_support( 'wc-product-gallery-slider' );
-		add_theme_support(
+		wc_get_container()->get( ThemeSupport::class )->add_default_options(
-			'woocommerce',
 			array(
 				'thumbnail_image_width' => 150,
 				'single_image_width'    => 300,

includes/theme-support/class-wc-twenty-nineteen.php

@@ -7,6 +7,7 @@
  */
 
 use Automattic\Jetpack\Constants;
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
 
 defined( 'ABSPATH' ) || exit;
 
@@ -37,8 +38,7 @@ class WC_Twenty_Nineteen {
 		add_theme_support( 'wc-product-gallery-zoom' );
 		add_theme_support( 'wc-product-gallery-lightbox' );
 		add_theme_support( 'wc-product-gallery-slider' );
-		add_theme_support(
+		wc_get_container()->get( ThemeSupport::class )->add_default_options(
-			'woocommerce',
 			array(
 				'thumbnail_image_width' => 300,
 				'single_image_width'    => 450,

includes/theme-support/class-wc-twenty-seventeen.php

@@ -7,6 +7,7 @@
  */
 
 use Automattic\Jetpack\Constants;
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
 
 defined( 'ABSPATH' ) || exit;
 
@@ -30,8 +31,7 @@ class WC_Twenty_Seventeen {
 		add_theme_support( 'wc-product-gallery-zoom' );
 		add_theme_support( 'wc-product-gallery-lightbox' );
 		add_theme_support( 'wc-product-gallery-slider' );
-		add_theme_support(
+		wc_get_container()->get( ThemeSupport::class )->add_default_options(
-			'woocommerce',
 			array(
 				'thumbnail_image_width' => 250,
 				'single_image_width'    => 350,

includes/theme-support/class-wc-twenty-sixteen.php

@@ -6,6 +6,8 @@
  * @package WooCommerce\Classes
  */
 
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
+
 defined( 'ABSPATH' ) || exit;
 
 /**
@@ -29,8 +31,7 @@ class WC_Twenty_Sixteen {
 		add_theme_support( 'wc-product-gallery-zoom' );
 		add_theme_support( 'wc-product-gallery-lightbox' );
 		add_theme_support( 'wc-product-gallery-slider' );
-		add_theme_support(
+		wc_get_container()->get( ThemeSupport::class )->add_default_options(
-			'woocommerce',
 			array(
 				'thumbnail_image_width' => 250,
 				'single_image_width'    => 400,

includes/theme-support/class-wc-twenty-ten.php

@@ -6,6 +6,8 @@
  * @package WooCommerce\Classes
  */
 
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
+
 defined( 'ABSPATH' ) || exit;
 
 /**
@@ -29,8 +31,7 @@ class WC_Twenty_Ten {
 		add_theme_support( 'wc-product-gallery-zoom' );
 		add_theme_support( 'wc-product-gallery-lightbox' );
 		add_theme_support( 'wc-product-gallery-slider' );
-		add_theme_support(
+		wc_get_container()->get( ThemeSupport::class )->add_default_options(
-			'woocommerce',
 			array(
 				'thumbnail_image_width' => 200,
 				'single_image_width'    => 300,

includes/theme-support/class-wc-twenty-thirteen.php

@@ -7,6 +7,8 @@
  * @package WooCommerce\Classes
  */
 
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
+
 defined( 'ABSPATH' ) || exit;
 
 /**
@@ -30,8 +32,7 @@ class WC_Twenty_Thirteen {
 		add_theme_support( 'wc-product-gallery-zoom' );
 		add_theme_support( 'wc-product-gallery-lightbox' );
 		add_theme_support( 'wc-product-gallery-slider' );
-		add_theme_support(
+		wc_get_container()->get( ThemeSupport::class )->add_default_options(
-			'woocommerce',
 			array(
 				'thumbnail_image_width' => 200,
 				'single_image_width'    => 300,

includes/theme-support/class-wc-twenty-twelve.php

@@ -7,6 +7,8 @@
  * @package WooCommerce\Classes
  */
 
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
+
 defined( 'ABSPATH' ) || exit;
 
 /**
@@ -30,8 +32,7 @@ class WC_Twenty_Twelve {
 		add_theme_support( 'wc-product-gallery-zoom' );
 		add_theme_support( 'wc-product-gallery-lightbox' );
 		add_theme_support( 'wc-product-gallery-slider' );
-		add_theme_support(
+		wc_get_container()->get( ThemeSupport::class )->add_default_options(
-			'woocommerce',
 			array(
 				'thumbnail_image_width' => 200,
 				'single_image_width'    => 300,

includes/theme-support/class-wc-twenty-twenty.php

@@ -7,6 +7,7 @@
  */
 
 use Automattic\Jetpack\Constants;
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
 
 defined( 'ABSPATH' ) || exit;
 
@@ -37,8 +38,7 @@ class WC_Twenty_Twenty {
 		add_theme_support( 'wc-product-gallery-zoom' );
 		add_theme_support( 'wc-product-gallery-lightbox' );
 		add_theme_support( 'wc-product-gallery-slider' );
-		add_theme_support(
+		wc_get_container()->get( ThemeSupport::class )->add_default_options(
-			'woocommerce',
 			array(
 				'thumbnail_image_width' => 450,
 				'single_image_width'    => 600,

includes/wc-core-functions.php

@@ -9,6 +9,7 @@
  */
 
 use Automattic\Jetpack\Constants;
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
 use Automattic\WooCommerce\Utilities\NumberUtil;
 
 if ( ! defined( 'ABSPATH' ) ) {
@@ -879,38 +880,7 @@ function wc_mail( $to, $subject, $message, $headers = "Content-Type: text/html\r
  * @return mixed  Value of prop(s).
  */
 function wc_get_theme_support( $prop = '', $default = null ) {
-	$theme_support = get_theme_support( 'woocommerce' );
+	return wc_get_container()->get( ThemeSupport::class )->get_option( $prop, $default );
-	$theme_support = is_array( $theme_support ) ? $theme_support[0] : false;
-
-	if ( ! $theme_support ) {
-		return $default;
-	}
-
-	if ( $prop ) {
-		$prop_stack = explode( '::', $prop );
-		$prop_key   = array_shift( $prop_stack );
-
-		if ( isset( $theme_support[ $prop_key ] ) ) {
-			$value = $theme_support[ $prop_key ];
-
-			if ( count( $prop_stack ) ) {
-				foreach ( $prop_stack as $prop_key ) {
-					if ( is_array( $value ) && isset( $value[ $prop_key ] ) ) {
-						$value = $value[ $prop_key ];
-					} else {
-						$value = $default;
-						break;
-					}
-				}
-			}
-		} else {
-			$value = $default;
-		}
-
-		return $value;
-	}
-
-	return $theme_support;
 }
 
 /**

src/Container.php

@@ -6,12 +6,13 @@
 namespace Automattic\WooCommerce;
 
 use Automattic\WooCommerce\Internal\DependencyManagement\ServiceProviders\ProxiesServiceProvider;
+use Automattic\WooCommerce\Internal\DependencyManagement\ServiceProviders\ThemeManagementServiceProvider;
 use Automattic\WooCommerce\Internal\DependencyManagement\ExtendedContainer;
 
 /**
  * PSR11 compliant dependency injection container for WooCommerce.
  *
- * Classes in the `src` directory should specify dependencies from that directory via constructor arguments
+ * Classes in the `src` directory should specify dependencies from that directory via an 'init' method having arguments
  * with type hints. If an instance of the container itself is needed, the type hint to use is \Psr\Container\ContainerInterface.
  *
  * Classes in the `src` directory should interact with anything outside (especially code in the `includes` directory
@@ -33,6 +34,7 @@ final class Container implements \Psr\Container\ContainerInterface {
 	 */
 	private $service_providers = array(
 		ProxiesServiceProvider::class,
+		ThemeManagementServiceProvider::class,
 	);
 
 	/**

src/Internal/DependencyManagement/ServiceProviders/ThemeManagementServiceProvider.php

@@ -0,0 +1,31 @@
+<?php
+/**
+ * ThemeManagementServiceProvider class file.
+ */
+
+namespace Automattic\WooCommerce\Internal\DependencyManagement\ServiceProviders;
+
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
+use Automattic\WooCommerce\Internal\DependencyManagement\AbstractServiceProvider;
+
+/**
+ * Service provider for the classes in the Automattic\WooCommerce\ThemeManagement namespace.
+ */
+class ThemeManagementServiceProvider extends AbstractServiceProvider {
+
+	/**
+	 * The classes/interfaces that are serviced by this service provider.
+	 *
+	 * @var array
+	 */
+	protected $provides = array(
+		ThemeSupport::class,
+	);
+
+	/**
+	 * Register the classes.
+	 */
+	public function register() {
+		$this->share_with_auto_arguments( ThemeSupport::class );
+	}
+}

src/ThemeManagement/ThemeSupport.php

@@ -0,0 +1,118 @@
+<?php
+/**
+ * ThemeSupport class file.
+ *
+ * @package Automattic\WooCommerce\ThemeManagement
+ */
+
+namespace Automattic\WooCommerce\ThemeManagement;
+
+use Automattic\WooCommerce\Proxies\LegacyProxy;
+use Automattic\WooCommerce\Utilities\ArrayUtil;
+
+/**
+ * Provides methods for theme support.
+ */
+class ThemeSupport {
+
+	const DEFAULTS_KEY = '_defaults';
+
+	/**
+	 * The instance of LegacyProxy to use.
+	 *
+	 * @var LegacyProxy
+	 */
+	private $legacy_proxy;
+
+	/**
+	 * ThemeSupport constructor.
+	 *
+	 * @internal
+	 * @param LegacyProxy $legacy_proxy The instance of LegacyProxy to use.
+	 */
+	final public function init( LegacyProxy $legacy_proxy ) {
+		$this->legacy_proxy = $legacy_proxy;
+	}
+
+	/**
+	 * Adds theme support options for the current theme.
+	 *
+	 * @param array $options The options to be added.
+	 */
+	public function add_options( $options ) {
+		$this->legacy_proxy->call_function( 'add_theme_support', 'woocommerce', $options );
+	}
+
+	/**
+	 * Adds default theme support options for the current theme.
+	 *
+	 * @param array $options The options to be added.
+	 */
+	public function add_default_options( $options ) {
+		$default_options = $this->get_option( self::DEFAULTS_KEY, array() );
+		$default_options = array_merge( $default_options, $options );
+		$this->add_options( array( self::DEFAULTS_KEY => $default_options ) );
+	}
+
+	/**
+	 * Gets "theme support" options from the current theme, if set.
+	 *
+	 * @param string $option_name Option name, possibly nested (key::subkey), to get specific value. Blank to get all the existing options as an array.
+	 * @param mixed  $default_value Value to return if the specified option doesn't exist.
+	 * @return mixed The retrieved option or the default value.
+	 */
+	public function get_option( $option_name = '', $default_value = null ) {
+		$theme_support_options = $this->get_all_options();
+
+		if ( ! $theme_support_options ) {
+			return $default_value;
+		}
+
+		if ( $option_name ) {
+			$value = ArrayUtil::get_nested_value( $theme_support_options, $option_name );
+			if ( is_null( $value ) ) {
+				$value = ArrayUtil::get_nested_value( $theme_support_options, self::DEFAULTS_KEY . '::' . $option_name, $default_value );
+			}
+			return $value;
+		}
+
+		return $theme_support_options;
+	}
+
+	/**
+	 * Checks whether a given theme support option has been defined.
+	 *
+	 * @param string $option_name The (possibly nested) name of the option to check.
+	 * @param bool   $include_defaults True to include the default values in the check, false otherwise.
+	 *
+	 * @return bool True if the specified theme support option has been defined, false otherwise.
+	 */
+	public function has_option( $option_name, $include_defaults = true ) {
+		$theme_support_options = $this->get_all_options();
+
+		if ( ! $theme_support_options ) {
+			return false;
+		}
+
+		$value = ArrayUtil::get_nested_value( $theme_support_options, $option_name );
+		if ( ! is_null( $value ) ) {
+			return true;
+		}
+
+		if ( ! $include_defaults ) {
+			return false;
+		}
+		$value = ArrayUtil::get_nested_value( $theme_support_options, self::DEFAULTS_KEY . '::' . $option_name );
+		return ! is_null( $value );
+	}
+
+	/**
+	 * Get all the defined theme support options for the 'woocommerce' feature.
+	 *
+	 * @return array An array with all the theme support options defined for the 'woocommerce' feature, or false if nothing has been defined for that feature.
+	 */
+	private function get_all_options() {
+		$theme_support = $this->legacy_proxy->call_function( 'get_theme_support', 'woocommerce' );
+		return is_array( $theme_support ) ? $theme_support[0] : false;
+	}
+}

src/Utilities/ArrayUtil.php

@@ -0,0 +1,48 @@
+<?php
+/**
+ * A class of utilities for dealing with arrays.
+ */
+
+namespace Automattic\WooCommerce\Utilities;
+
+/**
+ * A class of utilities for dealing with arrays.
+ */
+class ArrayUtil {
+	/**
+	 * Get a value from an nested array by specifying the entire key hierarchy with '::' as separator.
+	 *
+	 * E.g. for [ 'foo' => [ 'bar' => [ 'fizz' => 'buzz' ] ] ] the value for key 'foo::bar::fizz' would be 'buzz'.
+	 *
+	 * @param array  $array The array to get the value from.
+	 * @param string $key The complete key hierarchy, using '::' as separator.
+	 * @param mixed  $default The value to return if the key doesn't exist in the array.
+	 *
+	 * @return mixed The retrieved value, or the supplied default value.
+	 * @throws \Exception $array is not an array.
+	 */
+	public static function get_nested_value( array $array, string $key, $default = null ) {
+		$key_stack = explode( '::', $key );
+		$subkey    = array_shift( $key_stack );
+
+		if ( isset( $array[ $subkey ] ) ) {
+			$value = $array[ $subkey ];
+
+			if ( count( $key_stack ) ) {
+				foreach ( $key_stack as $subkey ) {
+					if ( is_array( $value ) && isset( $value[ $subkey ] ) ) {
+						$value = $value[ $subkey ];
+					} else {
+						$value = $default;
+						break;
+					}
+				}
+			}
+		} else {
+			$value = $default;
+		}
+
+		return $value;
+	}
+}
+

tests/legacy/bootstrap.php

@@ -103,7 +103,14 @@ class WC_Unit_Tests_Bootstrap {
 	 * @throws Exception Error when initializing one of the hacks.
 	 */
 	private function initialize_code_hacker() {
-		CodeHacker::initialize( array( __DIR__ . '/../../includes/' ) );
+		$wp_dir = getenv( 'WP_TESTS_WP_DIR' ) ? getenv( 'WP_TESTS_WP_DIR' ) : sys_get_temp_dir() . '/wordpress';
+		CodeHacker::initialize(
+			array(
+				$this->plugin_dir . '/includes/',
+				$wp_dir . '/wp-includes/class-wp-customize-manager.php',
+			)
+		);
+
 		$replaceable_functions = include_once __DIR__ . '/mockable-functions.php';
 		if ( ! empty( $replaceable_functions ) ) {
 			FunctionsMockerHack::initialize( $replaceable_functions );

tests/php/includes/customizer/class-wc-shop-customizer-test.php

@@ -0,0 +1,59 @@
+<?php
+/**
+ * Tests for WC_Shop_Customizer
+ */
+
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
+
+require_once ABSPATH . WPINC . '/class-wp-customize-manager.php';
+require_once ABSPATH . WPINC . '/class-wp-customize-control.php';
+
+/**
+ * Tests for WC_Shop_Customizer
+ */
+class WC_Shop_Customizer_Test extends WC_Unit_Test_Case {
+
+	/**
+	 * Runs before each test of the class.
+	 */
+	public function setUp() {
+		remove_theme_support( 'woocommerce' );
+	}
+
+	/**
+	 * @testdox add_sections should add controls for image size settings only if these sizes haven't been explicitly declared as theme support (not counting default declarations).
+	 *
+	 * @testWith ["single_image_width", true, false]
+	 *           ["single_image_width", false, true]
+	 *           ["thumbnail_image_width", true, false]
+	 *           ["thumbnail_image_width", false, true]
+	 *
+	 * @param string $option_name The option name to test, either 'single_image_width' or 'thumbnail_image_width'.
+	 * @param bool   $add_explicit_theme_support True to test when theme support is added explicitly (not as a default value).
+	 * @param bool   $expected_to_have_added_customization True to expect the customization to have been added, false to expect it no to have been added.
+	 */
+	public function test_add_sections_should_add_image_controls_only_if_no_theme_support_for_image_sizes_is_defined( $option_name, $add_explicit_theme_support, $expected_to_have_added_customization ) {
+		$customize_manager = $this->createMock( WP_Customize_Manager::class );
+		$added_settings    = array();
+		$added_controls    = array();
+
+		$add_setting_callback = function( $id, $args = array() ) use ( &$added_settings ) {
+			array_push( $added_settings, $id );
+		};
+		$add_control_callback = function( $id, $args = array() ) use ( &$added_controls ) {
+			array_push( $added_controls, $id );
+		};
+		$customize_manager->method( 'add_setting' )->will( $this->returnCallback( $add_setting_callback ) );
+		$customize_manager->method( 'add_control' )->will( $this->returnCallback( $add_control_callback ) );
+
+		$theme_support      = $this->get_instance_of( ThemeSupport::class );
+		$add_support_method = $add_explicit_theme_support ? 'add_options' : 'add_default_options';
+		$theme_support->$add_support_method( array( $option_name => 1234 ) );
+
+		$sut = $this->get_legacy_instance_of( WC_Shop_Customizer::class );
+		$sut->add_sections( $customize_manager );
+
+		$this->assertEquals( $expected_to_have_added_customization, in_array( 'woocommerce_' . $option_name, $added_settings, true ) );
+		$this->assertEquals( $expected_to_have_added_customization, in_array( 'woocommerce_' . $option_name, $added_controls, true ) );
+	}
+}

tests/php/src/ThemeSupport/ThemeSupportTest.php

@@ -0,0 +1,254 @@
+<?php
+/**
+ * Tests for ThemeSupport
+ *
+ * @package Automattic\WooCommerce\Tests\ThemeSupport
+ */
+
+namespace Automattic\WooCommerce\Tests\ThemeManagement;
+
+use Automattic\WooCommerce\ThemeManagement\ThemeSupport;
+
+/**
+ * Tests for ThemeSupport
+ */
+class ThemeSupportTest extends \WC_Unit_Test_Case {
+
+	/**
+	 * The system under test.
+	 *
+	 * @var ThemeSupport
+	 */
+	private $sut;
+
+	/**
+	 * Runs before each test.
+	 */
+	public function setUp() {
+		$this->sut = $this->get_instance_of( ThemeSupport::class );
+		remove_theme_support( 'woocommerce' );
+	}
+
+	/**
+	 * @testdox add_options should add the supplied options under the 'woocommerce' feature.
+	 */
+	public function test_add_options() {
+		$actual_added_feature = null;
+		$actual_added_options = null;
+
+		$this->register_legacy_proxy_function_mocks(
+			array(
+				'add_theme_support' => function( $feature, ...$args ) use ( &$actual_added_feature, &$actual_added_options ) {
+					$actual_added_feature = $feature;
+					$actual_added_options = $args;
+				},
+			)
+		);
+
+		$options = array( 'foo' => 'bar' );
+		$this->sut->add_options( $options );
+
+		$this->assertEquals( 'woocommerce', $actual_added_feature );
+		$this->assertEquals( $options, $actual_added_options[0] );
+
+		$this->reset_legacy_proxy_mocks();
+
+		$this->sut->add_options( $options );
+
+		$actual_retrieved_options = get_theme_support( 'woocommerce' )[0];
+		$this->assertEquals( $options, $actual_retrieved_options );
+	}
+
+	/**
+	 * @testdox add_default_options should add the supplied options under the 'woocommerce' feature on a '_defaults' key.
+	 */
+	public function test_2_add_default_options() {
+		$actual_added_options = array();
+
+		$this->register_legacy_proxy_function_mocks(
+			array(
+				'add_theme_support' => function( $feature, ...$args ) use ( &$actual_added_options ) {
+					array_push( $actual_added_options, $args );
+				},
+			)
+		);
+
+		$this->sut->add_default_options( array( 'foo' => 'bar' ) );
+		$this->sut->add_default_options( array( 'fizz' => 'buzz' ) );
+
+		$expected_added_options = array(
+			array(
+				array(
+					ThemeSupport::DEFAULTS_KEY =>
+						array(
+							'foo' => 'bar',
+						),
+				),
+			),
+			array(
+				array(
+					ThemeSupport::DEFAULTS_KEY =>
+						array(
+							'fizz' => 'buzz',
+						),
+				),
+			),
+		);
+
+		$this->assertEquals( $expected_added_options, $actual_added_options );
+
+		$this->reset_legacy_proxy_mocks();
+
+		$this->sut->add_default_options( array( 'foo' => 'bar' ) );
+		$this->sut->add_default_options( array( 'fizz' => 'buzz' ) );
+
+		$actual_retrieved_options   = get_theme_support( 'woocommerce' )[0];
+		$expected_retrieved_options = array(
+			ThemeSupport::DEFAULTS_KEY => array(
+				'foo'  => 'bar',
+				'fizz' => 'buzz',
+			),
+		);
+		$this->assertEquals( $expected_retrieved_options, $actual_retrieved_options );
+	}
+
+	/**
+	 * @testdox add_default_options should add the supplied options under the 'woocommerce' feature on a '_defaults' key.
+	 */
+	public function test_add_default_options() {
+		$this->sut->add_default_options( array( 'foo' => 'bar' ) );
+		$this->sut->add_default_options( array( 'fizz' => 'buzz' ) );
+
+		$actual   = get_theme_support( 'woocommerce' )[0];
+		$expected = array(
+			ThemeSupport::DEFAULTS_KEY => array(
+				'foo'  => 'bar',
+				'fizz' => 'buzz',
+			),
+		);
+		$this->assertEquals( $expected, $actual );
+	}
+
+	/**
+	 * @testdox get_option should return all the options under the 'woocommerce' feature when invoked with blank option name.
+	 */
+	public function test_get_option_with_no_option_name() {
+		$options = array( 'foo' => 'bar' );
+		$this->sut->add_options( $options );
+
+		$actual = $this->sut->get_option();
+		$this->assertEquals( $options, $actual );
+	}
+
+	/**
+	 * @testdox get_option should return null if no 'woocommerce' feature exists and no default value is supplied.
+	 */
+	public function test_get_option_with_no_option_name_when_no_options_exist_and_no_default_value_supplied() {
+		$actual = $this->sut->get_option();
+		$this->assertNull( $actual );
+	}
+
+	/**
+	 * @testdox get_option should return the supplied default value if no 'woocommerce' feature exists.
+	 */
+	public function test_get_option_with_no_option_name_when_no_options_exist_and_default_value_supplied() {
+		$actual = $this->sut->get_option( '', 'DEFAULT' );
+		$this->assertEquals( 'DEFAULT', $actual );
+	}
+
+	/**
+	 * @testdox get_theme_support should return the value of the requested option if it exists.
+	 */
+	public function test_get_theme_support_with_option_name() {
+		$options = array( 'foo' => array( 'bar' => 'fizz' ) );
+		$this->sut->add_options( $options );
+
+		$actual = $this->sut->get_option( 'foo::bar' );
+		$this->assertEquals( 'fizz', $actual );
+	}
+
+	/**
+	 * @testdox get_option should return null if the requested option doesn't exist and no default value is supplied.
+	 */
+	public function test_get_option_with_option_name_when_option_does_not_exist_and_no_default_value_supplied() {
+		$options = array( 'foo' => array( 'bar' => 'fizz' ) );
+		$this->sut->add_options( $options );
+
+		$actual = $this->sut->get_option( 'buzz' );
+		$this->assertNull( $actual );
+	}
+
+	/**
+	 * @testdox get_option should return the supplied default value if the requested option doesn't exist.
+	 */
+	public function test_get_option_with_option_name_when_option_does_not_exist_and_default_value_supplied() {
+		$options = array( 'foo' => array( 'bar' => 'fizz' ) );
+		$this->sut->add_options( $options );
+
+		$actual = $this->sut->get_option( 'buzz', 'DEFAULT' );
+		$this->assertEquals( 'DEFAULT', $actual );
+	}
+
+	/**
+	 * @testdox get_option should return the value of the requested option if it has been defined as a default.
+	 */
+	public function test_get_option_with_option_name_and_option_defined_as_default() {
+		$options = array( 'foo' => array( 'bar' => 'fizz' ) );
+		$this->sut->add_default_options( $options );
+
+		$actual = $this->sut->get_option( 'foo::bar' );
+		$this->assertEquals( 'fizz', $actual );
+	}
+
+	/**
+	 * @testdox has_option should return false if no 'woocommerce' feature exists.
+	 *
+	 * @testWith [true]
+	 *           [false]
+	 *
+	 * @param bool $include_defaults Whether to include defaults in the search or not.
+	 */
+	public function test_has_option_when_no_woocommerce_feature_is_defined( $include_defaults ) {
+		$this->assertFalse( $this->sut->has_option( 'foo::bar', $include_defaults ) );
+	}
+
+	/**
+	 * @testdox has_option should return false if the specified option has not been defined.
+	 *
+	 * @testWith [true]
+	 *           [false]
+	 *
+	 * @param bool $include_defaults Whether to include defaults in the search or not.
+	 */
+	public function test_has_option_when_option_is_not_defined( $include_defaults ) {
+		$this->sut->add_options( array( 'foo' => 'bar' ) );
+		$this->assertFalse( $this->sut->has_option( 'fizz::buzz', $include_defaults ) );
+	}
+
+	/**
+	 * @testdox has_option should return true if the specified option has been defined.
+	 *
+	 * @testWith [true]
+	 *           [false]
+	 *
+	 * @param bool $include_defaults Whether to include defaults in the search or not.
+	 */
+	public function test_has_option_when_option_is_defined( $include_defaults ) {
+		$this->sut->add_options( array( 'foo' => 'bar' ) );
+		$this->assertTrue( $this->sut->has_option( 'foo', $include_defaults ) );
+	}
+
+	/**
+	 * @testdox If an option has been defined as a default, has_theme_support should return true if $include_defaults is passed as true, should return false otherwise.
+	 *
+	 * @testWith [true, true]
+	 *           [false, false]
+	 *
+	 * @param bool $include_defaults Whether to include defaults in the search or not.
+	 * @param bool $expected_result The expected return value from the tested method.
+	 */
+	public function test_has_option_when_option_is_defined_as_default( $include_defaults, $expected_result ) {
+		$this->sut->add_default_options( array( 'foo' => 'bar' ) );
+		$this->assertEquals( $expected_result, $this->sut->has_option( 'foo', $include_defaults ) );
+	}
+}

tests/php/src/Utilities/ArrayUtilTest.php

@@ -0,0 +1,66 @@
+<?php
+
+namespace Automattic\WooCommerce\Tests\Utilities;
+
+use Automattic\WooCommerce\Utilities\ArrayUtil;
+
+/**
+ * A collection of tests for the array utility class.
+ */
+class ArrayUtilTest extends \WC_Unit_Test_Case {
+	/**
+	 * @testdox `get_nested_value` should return null if the requested key doesn't exist and no default value is supplied.
+	 *
+	 * @testWith ["foo"]
+	 *           ["foo::bar"]
+	 *
+	 * @param string $key The key to test.
+	 */
+	public function test_get_nested_value_returns_null_if_non_existing_key_and_default_not_supplied( $key ) {
+		$array  = array( 'fizz' => 'buzz' );
+		$actual = ArrayUtil::get_nested_value( $array, $key );
+
+		$this->assertNull( $actual );
+	}
+
+	/**
+	 * @testdox `get_nested_value` should return the supplied default value if the requested key doesn't exist.
+	 *
+	 * @testWith ["foo"]
+	 *           ["foo::bar"]
+	 *
+	 * @param string $key The key to test.
+	 */
+	public function test_get_nested_value_returns_supplied_default_if_non_existing_key( $key ) {
+		$array  = array( 'fizz' => 'buzz' );
+		$actual = ArrayUtil::get_nested_value( $array, $key, 'DEFAULT' );
+
+		$this->assertEquals( 'DEFAULT', $actual );
+	}
+
+	/**
+	 * @testdox `get_nested_value` should return the proper value when a simple key is passed.
+	 */
+	public function test_get_nested_value_works_for_simple_keys() {
+		$array  = array( 'foo' => 'bar' );
+		$actual = ArrayUtil::get_nested_value( $array, 'foo' );
+
+		$this->assertEquals( 'bar', $actual );
+	}
+
+	/**
+	 * @testdox `get_nested_value` should return the proper value when a nested key is passed.
+	 */
+	public function test_get_nested_value_works_for_nested_keys() {
+		$array  = array(
+			'foo' => array(
+				'bar' => array(
+					'fizz' => 'buzz',
+				),
+			),
+		);
+		$actual = ArrayUtil::get_nested_value( $array, 'foo::bar::fizz' );
+
+		$this->assertEquals( 'buzz', $actual );
+	}
+}