Add CheckoutMock class

plugins/woocommerce/tests/php/src/Blocks/Mocks/CheckoutMock.php

@@ -0,0 +1,21 @@
+<?php
+declare( strict_types = 1 );
+
+namespace Automattic\WooCommerce\Tests\Blocks\Mocks;
+
+use Automattic\WooCommerce\Blocks\BlockTypes\Checkout;
+
+/**
+ * A mock class.
+ */
+class CheckoutMock extends Checkout {
+
+	/**
+	 * Mock the enqueue_data method so we can call it from tests.
+	 *
+	 * @return void
+	 */
+	public function mock_enqueue_data() {
+		$this->enqueue_data();
+	}
+}