[WIP] Create tests for custom checkout permalink

tests/Unit/CheckoutTest.php

@@ -0,0 +1,90 @@
+<?php
+declare( strict_types=1 );
+
+use WooCommerce\Facebook\Checkout;
+
+/**
+ * Checkout unit test class.
+ */
+class CheckoutTest extends WP_UnitTestCase {
+
+    /**
+     * Instance of the Checkout class.
+     *
+     * @var Checkout
+     */
+    protected $checkout;
+
+    /**
+     * Set up the test environment.
+     *
+     * @return void
+     */
+    public function setUp(): void {
+        parent::setUp();
+        $this->checkout = new Checkout();
+        $this->checkout->add_checkout_permalink_rewrite_rule();
+
+        flush_rewrite_rules();
+    }
+
+    /**
+     * Test if hooks are added correctly.
+     *
+     * @return void
+     */
+    public function test_hooks_are_added() {
+        $this->assertGreaterThan(0, has_action('init', [$this->checkout, 'add_checkout_permalink_rewrite_rule']));
+        $this->assertGreaterThan(0, has_filter('query_vars', [$this->checkout, 'add_checkout_permalink_query_var']));
+        $this->assertGreaterThan(0, has_filter('template_include', [$this->checkout, 'load_checkout_permalink_template']));
+    }
+
+    /**
+     * Test if query vars are added correctly.
+     *
+     * @return void
+     */
+    public function test_add_checkout_permalink_query_var() {
+        $vars = apply_filters('query_vars', []);
+
+        $this->assertContains('fb_checkout', $vars);
+        $this->assertContains('products', $vars);
+        $this->assertContains('coupon', $vars);
+    }
+
+    /**
+     * Test if rewrite rules are added correctly.
+     *
+     * @return void
+     */
+    public function test_add_checkout_permalink_rewrite_rule() {
+        global $wp_rewrite;
+
+        $wp_rewrite->flush_rules();
+        $rules = $wp_rewrite->wp_rewrite_rules();
+
+        $this->assertIsArray($rules, 'Rewrite rules should be an array');
+        $this->assertArrayHasKey('^fb-checkout/?$', $rules);
+        $this->assertEquals('index.php?fb_checkout=1', $rules['^fb-checkout/?$']);
+    }
+
+    /**
+     * Test if rewrite rules are flushed on activation.
+     *
+     * @return void
+     */
+    public function test_flush_rewrite_rules_on_activation() {
+        $this->checkout->flush_rewrite_rules_on_activation();
+        $this->assertTrue(did_action('flush_rewrite_rules'));
+    }
+
+    /**
+     * Test if rewrite rules are flushed on deactivation.
+     *
+     * @return void
+     */
+    public function test_flush_rewrite_rules_on_deactivation() {
+        $this->checkout->flush_rewrite_rules_on_deactivation();
+        $this->assertTrue(did_action('flush_rewrite_rules'));
+    }
+}