diff --git a/src/Hooks/CheckoutScriptHooks.php b/src/Hooks/CheckoutScriptHooks.php
index 0fb775cf5..8ff9d2187 100644
--- a/src/Hooks/CheckoutScriptHooks.php
+++ b/src/Hooks/CheckoutScriptHooks.php
@@ -195,11 +195,19 @@ private function shouldShowDeliveryOptions(): bool
 
         $showDeliveryOptions = false;
 
+        $deliveryOptionsEnabledWhenOnBackorder = Settings::get(
+            CheckoutSettings::ENABLE_DELIVERY_OPTIONS_WHEN_NOT_IN_STOCK,
+            CheckoutSettings::ID
+        );
+
         foreach (WC()->cart->get_cart() as $cartItem) {
             /**  @var WC_Product $product */
             $product = $cartItem['data'];
 
-            if (! $product->is_virtual() && ! $product->is_on_backorder($cartItem['quantity'])) {
+            $productIsVirtual   = $product->is_virtual();
+            $productOnBackorder = $product->is_on_backorder($cartItem['quantity']);
+
+            if (! $productIsVirtual && (! $productOnBackorder || $deliveryOptionsEnabledWhenOnBackorder)) {
                 $showDeliveryOptions = true;
                 break;
             }
diff --git a/tests/Mock/MockWcCart.php b/tests/Mock/MockWcCart.php
index b7e2d0a82..cefa53902 100644
--- a/tests/Mock/MockWcCart.php
+++ b/tests/Mock/MockWcCart.php
@@ -34,11 +34,24 @@ public function add_to_cart(
         array $variation = [],
         array $cartItemData = []
     ): void {
-        for ($i = 0; $i < $quantity; $i++) {
-            $this->items[] = new WC_Product($productId);
+        $cartId      = $this->generate_cart_id($productId, $variationId, $variation, $cartItemData);
+        $cartItemKey = $this->find_product_in_cart($cartId);
+
+        if ($cartItemKey) {
+            $this->items[$cartItemKey]['quantity'] += $quantity;
+        } else {
+            $this->items[] = [
+                'data'     => new WC_Product($productId),
+                'quantity' => $quantity,
+            ];
         }
     }
 
+    public function get_cart()
+    {
+        return $this->items;
+    }
+
     /**
      * @return void
      */
@@ -53,13 +66,12 @@ public function empty_cart(): void
     public function get_shipping_packages(): array
     {
         // calculate weight of all products in cart
-        $weight = array_reduce(
-            $this->items,
-            static function (float $carry, WC_Product $item) {
-                return $carry + (float) $item->get_weight();
-            },
-            0
-        );
+        $weight = 0;
+        foreach ($this->items as $item) {
+            /** @var \WC_Product $wcProduct */
+            $wcProduct = $item['data'];
+            $weight    += $wcProduct->get_weight() * $item['quantity'];
+        }
 
         if ($weight > 10) {
             return [];
@@ -69,4 +81,72 @@ static function (float $carry, WC_Product $item) {
             'flat_rate:0' => [],
         ];
     }
+
+    /**
+     * Generate a unique ID for the cart item being added.
+     *
+     * @param  int   $productId    - id of the product the key is being generated for.
+     * @param  int   $variationId  of the product the key is being generated for.
+     * @param  array $variation    data for the cart item.
+     * @param  array $cartItemData other cart item data passed which affects this items uniqueness in the cart.
+     *
+     * @return string cart item key
+     */
+    public function generate_cart_id(
+        int   $productId,
+        int   $variationId = 0,
+        array $variation = [],
+        array $cartItemData = []
+    ): string {
+        $idParts = [$productId];
+
+        if ($variationId && 0 !== $variationId) {
+            $idParts[] = $variationId;
+        }
+
+        if (is_array($variation) && ! empty($variation)) {
+            $variationKey = '';
+            foreach ($variation as $key => $value) {
+                $variationKey .= trim($key) . trim($value);
+            }
+            $idParts[] = $variationKey;
+        }
+
+        if (is_array($cartItemData) && ! empty($cartItemData)) {
+            $cartItemDataKey = '';
+            foreach ($cartItemData as $key => $value) {
+                if (is_array($value) || is_object($value)) {
+                    $value = http_build_query($value);
+                }
+                $cartItemDataKey .= trim($key) . trim($value);
+            }
+            $idParts[] = $cartItemDataKey;
+        }
+
+        return apply_filters(
+            'woocommerce_cart_id',
+            md5(implode('_', $idParts))
+        );
+    }
+
+    /**
+     * Check if product is in the cart and return cart item key.
+     * Cart item key will be unique based on the item and its properties, such as variations.
+     * ONLY RETURNS A KEY! DOES NOT RETURN THE ITEM!
+     *
+     * @param  mixed $cartId id of product to find in the cart.
+     *
+     * @return string cart item key
+     */
+    public function find_product_in_cart($cartId = false): string
+    {
+        $thisItemsIsArray  = is_array($this->items);
+        $itemAlreadyExists = isset($this->items[$cartId]);
+
+        if ($cartId !== false && $thisItemsIsArray && $itemAlreadyExists) {
+            return $cartId;
+        }
+
+        return '';
+    }
 }
diff --git a/tests/Mock/MockWpEnqueue.php b/tests/Mock/MockWpEnqueue.php
new file mode 100644
index 000000000..e459fdb3f
--- /dev/null
+++ b/tests/Mock/MockWpEnqueue.php
@@ -0,0 +1,93 @@
+<?php
+
+declare(strict_types=1);
+
+namespace MyParcelNL\WooCommerce\Tests\Mock;
+
+use MyParcelNL\Pdk\Base\Support\Arr;
+use MyParcelNL\Pdk\Base\Support\Collection;
+
+final class MockWpEnqueue implements StaticMockInterface
+{
+    /**
+     * @var \MyParcelNL\Pdk\Base\Support\Collection
+     */
+    private static $queuedItems;
+
+    /**
+     * @param $handle
+     * @param $src
+     * @param $deps
+     * @param $ver
+     * @param $in_footer
+     *
+     * @return void
+     */
+    public static function add($handle, $src, $deps, $ver, $in_footer): void
+    {
+        $existing = array_filter(Arr::wrap(self::get($handle)));
+
+        self::$queuedItems->put(
+            $handle,
+            array_merge($existing, [
+                [
+                    'src' => $src,
+                    'deps' => $deps,
+                    'ver' => $ver,
+                    'in_footer' => $in_footer,
+                ],
+            ])
+        );
+    }
+
+    /**
+     * @return \MyParcelNL\Pdk\Base\Support\Collection
+     */
+    public static function all(): Collection
+    {
+        return self::getQueuedItems();
+    }
+
+    /**
+     * @param  string $tag
+     *
+     * @return array
+     */
+    public static function get(string $tag): array
+    {
+        return self::getQueuedItems()
+            ->get($tag, []);
+    }
+
+    public static function reset(): void
+    {
+        self::$queuedItems = new Collection();
+    }
+
+    public static function toArray(): array
+    {
+        return self::getQueuedItems()
+            ->map(static function (array $actions) {
+                return (new Collection(Arr::pluck($actions, 'function')))->map(static function ($function) {
+                    if (! is_array($function)) {
+                        return $function;
+                    }
+
+                    return implode('::', [get_class($function[0]), $function[1]]);
+                });
+            })
+            ->toArray();
+    }
+
+    /**
+     * @return \MyParcelNL\Pdk\Base\Support\Collection
+     */
+    private static function getQueuedItems(): Collection
+    {
+        if (null === self::$queuedItems) {
+            self::reset();
+        }
+
+        return self::$queuedItems;
+    }
+}
diff --git a/tests/Unit/Hooks/CheckoutScriptHooksTest.php b/tests/Unit/Hooks/CheckoutScriptHooksTest.php
new file mode 100644
index 000000000..4d1703b3f
--- /dev/null
+++ b/tests/Unit/Hooks/CheckoutScriptHooksTest.php
@@ -0,0 +1,83 @@
+<?php
+/** @noinspection StaticClosureCanBeUsedInspection */
+
+declare(strict_types=1);
+
+namespace MyParcelNL\WooCommerce\Hooks;
+
+use MyParcelNL\Pdk\Facade\Pdk;
+use MyParcelNL\Pdk\Settings\Model\CheckoutSettings;
+use MyParcelNL\WooCommerce\Tests\Mock\MockWpEnqueue;
+use MyParcelNL\WooCommerce\Tests\Uses\UsesMockWcPdkInstance;
+use WC_Product;
+use function MyParcelNL\Pdk\Tests\factory;
+use function MyParcelNL\Pdk\Tests\usesShared;
+use function MyParcelNL\WooCommerce\Tests\wpFactory;
+
+usesShared(new UsesMockWcPdkInstance());
+
+it(
+    'enqueues frontend scripts',
+    function (
+        bool  $enableDeliveryOptions,
+        bool  $enableDeliveryOptionsWhenNotInStock,
+        array $productData,
+        array $expected
+    ) {
+        factory(CheckoutSettings::class)
+            ->withEnableDeliveryOptions($enableDeliveryOptions)
+            ->withEnableDeliveryOptionsWhenNotInStock($enableDeliveryOptionsWhenNotInStock)
+            ->store();
+
+        $product = wpFactory(WC_Product::class)
+            ->with($productData)
+            ->make();
+
+        WC()->cart->add_to_cart($product->get_id(), 2);
+
+        /** @var \MyParcelNL\WooCommerce\Hooks\CheckoutScriptHooks $class */
+        $class = Pdk::get(CheckoutScriptHooks::class);
+
+        $class->enqueueFrontendScripts();
+
+        $all =
+            MockWpEnqueue::all()
+                ->all();
+
+        expect($all)
+            ->toHaveKeys($expected['toContain'])
+            ->and($all)->not->toHaveKeys($expected['notToContain']);
+
+        MockWpEnqueue::reset();
+        WC()->cart->empty_cart();
+    }
+)
+    ->with([
+        'enable all, in stock'                  => [
+            'enableDeliveryOptions'               => true,
+            'enableDeliveryOptionsWhenNotInStock' => true,
+            'productData'                         => ['id' => 1, 'is_on_backorder' => false],
+            'expected'                            => [
+                'toContain'    => ['myparcelnl-delivery-options'],
+                'notToContain' => [],
+            ],
+        ],
+        'enable delivery options, on backorder' => [
+            'enableDeliveryOptions'               => true,
+            'enableDeliveryOptionsWhenNotInStock' => false,
+            'productData'                         => ['id' => 1, 'is_on_backorder' => true],
+            'expected'                            => [
+                'toContain'    => [],
+                'notToContain' => ['myparcelnl-delivery-options'],
+            ],
+        ],
+        'enable all, on backorder'              => [
+            'enableDeliveryOptions'               => true,
+            'enableDeliveryOptionsWhenNotInStock' => true,
+            'productData'                         => ['id' => 1, 'is_on_backorder' => true],
+            'expected'                            => [
+                'toContain'    => ['myparcelnl-delivery-options'],
+                'notToContain' => [],
+            ],
+        ],
+    ]);
diff --git a/tests/__snapshots__/ProductSettingsMigrationTest__it_migrates_pre_v5.0.0_product_settings_with_data_set_simple_product_with_all_settings__1.json b/tests/__snapshots__/ProductSettingsMigrationTest__it_migrates_pre_v5.0.0_product_settings_with_data_set_simple_product_with_all_settings__1.json
index 5bdb8013c..f551bf49a 100644
--- a/tests/__snapshots__/ProductSettingsMigrationTest__it_migrates_pre_v5.0.0_product_settings_with_data_set_simple_product_with_all_settings__1.json
+++ b/tests/__snapshots__/ProductSettingsMigrationTest__it_migrates_pre_v5.0.0_product_settings_with_data_set_simple_product_with_all_settings__1.json
@@ -51,8 +51,8 @@
       "value": ["5.0.0-alpha.1"]
     }
   ],
+  "parentProduct": null,
   "product": {
-    "id": "product",
     "countryOfOrigin": "BB",
     "customsCode": "1234",
     "disableDeliveryOptions": -1,
@@ -66,7 +66,7 @@
     "exportSignature": -1,
     "fitInDigitalStamp": 7,
     "fitInMailbox": 7,
+    "id": "product",
     "packageType": "digital_stamp"
-  },
-  "parentProduct": null
+  }
 }
diff --git a/tests/mock_wp_functions.php b/tests/mock_wp_functions.php
index 5eba63275..a76c5b3c1 100644
--- a/tests/mock_wp_functions.php
+++ b/tests/mock_wp_functions.php
@@ -6,6 +6,7 @@
 use MyParcelNL\Pdk\Facade\Pdk;
 use MyParcelNL\WooCommerce\Tests\Exception\DieException;
 use MyParcelNL\WooCommerce\Tests\Mock\MockWpActions;
+use MyParcelNL\WooCommerce\Tests\Mock\MockWpEnqueue;
 use MyParcelNL\WooCommerce\Tests\Mock\MockWpMeta;
 use MyParcelNL\WooCommerce\Tests\Mock\MockWpUser;
 use MyParcelNL\WooCommerce\Tests\Mock\WordPressOptions;
@@ -151,3 +152,13 @@ function wp_unslash($value)
 {
     return $value;
 }
+
+function wp_enqueue_script($handle, $src = '', $deps = [], $ver = false, $in_footer = false)
+{
+    MockWpEnqueue::add($handle, $src, $deps, $ver, $in_footer);
+}
+
+function wp_enqueue_style($handle, $src, $deps, $version, $media)
+{
+    MockWpEnqueue::add($handle, $src, $deps, $version, $media);
+}
\ No newline at end of file