From 1e5412adce71cbe22712a3a00e4b391ad654e416 Mon Sep 17 00:00:00 2001
From: scruffian <ben@scruffian.com>
Date: Wed, 1 Mar 2023 10:56:14 +0000
Subject: [PATCH 01/37] Navigation: Always create a fallback navigation menu on
 every page load

---
 .../src/navigation/edit/index.js              | 66 -------------------
 .../block-library/src/navigation/index.php    | 34 +++++++---
 2 files changed, 26 insertions(+), 74 deletions(-)

diff --git a/packages/block-library/src/navigation/edit/index.js b/packages/block-library/src/navigation/edit/index.js
index 027b3b87a0a8a7..10055770dcf856 100644
--- a/packages/block-library/src/navigation/edit/index.js
+++ b/packages/block-library/src/navigation/edit/index.js
@@ -41,7 +41,6 @@ import {
 } from '@wordpress/components';
 import { __, sprintf } from '@wordpress/i18n';
 import { speak } from '@wordpress/a11y';
-import { createBlock, getBlockType } from '@wordpress/blocks';
 import { close, Icon } from '@wordpress/icons';
 
 /**
@@ -308,71 +307,6 @@ function Navigation( {
 	// that automatically saves the menu as an entity when changes are made to the inner blocks.
 	const hasUnsavedBlocks = hasUncontrolledInnerBlocks && ! isEntityAvailable;
 
-	useEffect( () => {
-		if (
-			ref ||
-			! hasResolvedNavigationMenus ||
-			isConvertingClassicMenu ||
-			fallbackNavigationMenus?.length > 0 ||
-			hasUnsavedBlocks
-		) {
-			return;
-		}
-
-		// If there's non fallback navigation menus and
-		// a classic menu with a `primary` location or slug,
-		// then create a new navigation menu based on it.
-		// Otherwise, use the most recently created classic menu.
-		if ( classicMenus?.length ) {
-			const primaryMenus = classicMenus.filter(
-				( classicMenu ) =>
-					classicMenu.locations.includes( 'primary' ) ||
-					classicMenu.slug === 'primary'
-			);
-
-			if ( primaryMenus.length ) {
-				convertClassicMenu(
-					primaryMenus[ 0 ].id,
-					primaryMenus[ 0 ].name,
-					'publish'
-				);
-			} else {
-				classicMenus.sort( ( a, b ) => {
-					return b.id - a.id;
-				} );
-				convertClassicMenu(
-					classicMenus[ 0 ].id,
-					classicMenus[ 0 ].name,
-					'publish'
-				);
-			}
-		} else {
-			// If there are no fallback navigation menus and no classic menus,
-			// then create a new navigation menu.
-
-			// Check that we have a page-list block type.
-			let defaultBlocks = [];
-			if ( getBlockType( 'core/page-list' ) ) {
-				defaultBlocks = [ createBlock( 'core/page-list' ) ];
-			}
-
-			createNavigationMenu(
-				'Navigation', // TODO - use the template slug in future
-				defaultBlocks,
-				'publish'
-			);
-		}
-	}, [
-		hasResolvedNavigationMenus,
-		hasUnsavedBlocks,
-		classicMenus,
-		convertClassicMenu,
-		createNavigationMenu,
-		fallbackNavigationMenus?.length,
-		isConvertingClassicMenu,
-		ref,
-	] );
-
 	const navRef = useRef();
 
 	// The standard HTML5 tag for the block wrapper.
diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index 5ec43046d6618f..9c7a1603086fdd 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -463,15 +463,14 @@ function block_core_navigation_get_default_pages_fallback() {
 }
 
 /**
- * Retrieves the appropriate fallback to be used on the front of the
- * site when there is no menu assigned to the Nav block.
- *
- * This aims to mirror how the fallback mechanic for wp_nav_menu works.
- * See https://developer.wordpress.org/reference/functions/wp_nav_menu/#more-information.
- *
- * @return array the array of blocks to be used as a fallback.
+ * Creates the appropriate fallback to be used on the front of the site.
  */
-function block_core_navigation_get_fallback_blocks() {
+function block_core_navigation_create_fallback() {
+	$should_skip = apply_filters( 'block_core_navigation_skip_fallback', false );
+	if ( $should_skip ) {
+		return;
+	}
+
 	// Get the most recently published Navigation post.
 	$navigation_post = block_core_navigation_get_most_recently_published_navigation();
 
@@ -485,6 +484,21 @@ function block_core_navigation_get_fallback_blocks() {
 	if ( ! $navigation_post ) {
 		$navigation_post = block_core_navigation_get_default_pages_fallback();
 	}
+}
+
+
+/**
+ * Retrieves the appropriate fallback to be used on the front of the
+ * site when there is no menu assigned to the Nav block.
+ *
+ * This aims to mirror how the fallback mechanic for wp_nav_menu works.
+ * See https://developer.wordpress.org/reference/functions/wp_nav_menu/#more-information.
+ *
+ * @return array the array of blocks to be used as a fallback.
+ */
+function block_core_navigation_get_fallback_blocks() {
+	// Get the most recently published Navigation post.
+	$navigation_post = block_core_navigation_get_most_recently_published_navigation();
 
 	// Use the first non-empty Navigation as fallback, there should always be one.
 	if ( $navigation_post ) {
@@ -899,3 +913,7 @@ function block_core_navigation_typographic_presets_backcompatibility( $parsed_bl
 }
 
 add_filter( 'render_block_data', 'block_core_navigation_typographic_presets_backcompatibility' );
+
+// We have to aply this action on both init and admin init, as the code loads after init when in wp-admin.
+add_action( 'init', 'block_core_navigation_create_fallback' );
+add_action( 'admin_init', 'block_core_navigation_create_fallback' );

From 78ae0b1f9ac6a704d39898239255896aa9d847b0 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 14:47:05 +0000
Subject: [PATCH 02/37] Add basic unit tests

---
 .../block-library/src/navigation/index.php    |  2 +
 phpunit/navigation-block-fallback-test.php    | 42 +++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 phpunit/navigation-block-fallback-test.php

diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index 9c7a1603086fdd..506b05d522dc6e 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -484,6 +484,8 @@ function block_core_navigation_create_fallback() {
 	if ( ! $navigation_post ) {
 		$navigation_post = block_core_navigation_get_default_pages_fallback();
 	}
+
+	return $navigation_post;
 }
 
 
diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
new file mode 100644
index 00000000000000..c4f26a1e377b84
--- /dev/null
+++ b/phpunit/navigation-block-fallback-test.php
@@ -0,0 +1,42 @@
+<?php
+/**
+ * Tests Fallback Behavior for Navigation block
+ *
+ * @package WordPress
+ */
+
+class Tests_Block_Navigation_Fallbacks extends WP_UnitTestCase {
+	public function set_up() {
+		parent::set_up();
+		switch_theme( 'emptytheme' );
+	}
+
+	public static function wpSetUpBeforeClass() {
+
+	}
+
+	public static function wpTearDownAfterClass() {
+
+	}
+
+	public function test_creates_fallback_with_page_list_by_default() {
+		$fallback = gutenberg_block_core_navigation_create_fallback();
+
+		$this->assertEquals( $fallback->post_type, 'wp_navigation' );
+		$this->assertEquals( $fallback->post_title, 'Navigation' );
+		$this->assertEquals( $fallback->post_content, '<!-- wp:page-list /-->' );
+		$this->assertEquals( $fallback->post_status, 'publish' );
+	}
+
+	public function test_skip_if_filter_returns_truthy() {
+		add_filter( 'block_core_navigation_skip_fallback', '__return_true' );
+
+		$actual = gutenberg_block_core_navigation_create_fallback();
+
+		$this->assertEquals( $actual, null );
+
+		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );
+	}
+}
+
+

From 83d1ac3200774fbf5450d873ce481e0bcb5ba63e Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 15:13:14 +0000
Subject: [PATCH 03/37] Fix Classic Meny fallback to use Menu title not slug

---
 packages/block-library/src/navigation/index.php | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index 506b05d522dc6e..82fc92d1758e48 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -344,6 +344,7 @@ function block_core_navigation_maybe_use_classic_menu_fallback() {
 		return;
 	}
 
+
 	// Create a new navigation menu from the classic menu.
 	$wp_insert_post_result = wp_insert_post(
 		array(
@@ -356,6 +357,9 @@ function block_core_navigation_maybe_use_classic_menu_fallback() {
 		true // So that we can check whether the result is an error.
 	);
 
+
+
+
 	if ( is_wp_error( $wp_insert_post_result ) ) {
 		return;
 	}

From d68c93a6679b9abad7895fb13f1ebd0afa8f9899 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 15:13:22 +0000
Subject: [PATCH 04/37] Add tests for Classic Menu

---
 phpunit/navigation-block-fallback-test.php | 69 +++++++++++++++++++++-
 1 file changed, 66 insertions(+), 3 deletions(-)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index c4f26a1e377b84..ae821ef92dd78c 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -6,6 +6,15 @@
  */
 
 class Tests_Block_Navigation_Fallbacks extends WP_UnitTestCase {
+
+	/**
+	 * @var WP_Post
+	 */
+	protected static $navigation_post;
+
+
+
+
 	public function set_up() {
 		parent::set_up();
 		switch_theme( 'emptytheme' );
@@ -16,10 +25,12 @@ public static function wpSetUpBeforeClass() {
 	}
 
 	public static function wpTearDownAfterClass() {
-
+		if ( ! empty( self::$post_with_comments_disabled->ID ) ) {
+			wp_delete_post( self::$navigation_post->ID, true );
+		}
 	}
 
-	public function test_creates_fallback_with_page_list_by_default() {
+	public function test_creates_fallback_navigation_with_page_list_by_default() {
 		$fallback = gutenberg_block_core_navigation_create_fallback();
 
 		$this->assertEquals( $fallback->post_type, 'wp_navigation' );
@@ -28,11 +39,63 @@ public function test_creates_fallback_with_page_list_by_default() {
 		$this->assertEquals( $fallback->post_status, 'publish' );
 	}
 
-	public function test_skip_if_filter_returns_truthy() {
+	public function test_gets_fallback_navigation_with_existing_navigation_menu_if_found() {
+
+		self::$navigation_post = self::factory()->post->create_and_get(
+			array(
+				'post_type'    => 'wp_navigation',
+				'post_title'   => 'Existing Navigation Menu',
+				'post_content' => '<!-- wp:page-list /-->',
+			)
+		);
+
+		$fallback = gutenberg_block_core_navigation_create_fallback();
+
+		$this->assertEquals( $fallback->post_title, self::$navigation_post->post_title );
+		$this->assertEquals( $fallback->post_type, self::$navigation_post->post_type );
+		$this->assertEquals( $fallback->post_content, self::$navigation_post->post_content );
+		$this->assertEquals( $fallback->post_status, self::$navigation_post->post_status );
+	}
+
+	public function test_gets_fallback_navigation_with_existing_classic_menu_if_found() {
+
+		$menu_id = wp_create_nav_menu( 'Existing Classic Menu' );
+
+		wp_update_nav_menu_item(
+			$menu_id,
+			0,
+			array(
+				'menu-item-title'  => 'Classic Menu Item 1',
+				'menu-item-url'    => '/classic-menu-item-1',
+				'menu-item-status' => 'publish',
+			)
+		);
+
+		$fallback = gutenberg_block_core_navigation_create_fallback();
+
+		$this->assertEquals( 'Existing Classic Menu', $fallback->post_title, );
+		$this->assertEquals( 'wp_navigation', $fallback->post_type, );
+		$this->assertEquals( 'publish', $fallback->post_status );
+
+		// Assert that the fallback contains a navigation-link block.
+		$this->assertStringContainsString( '<!-- wp:navigation-link', $fallback->post_content );
+
+		// Assert that fallback post_content contains the expected menu item title.
+		$this->assertStringContainsString( '"label":"Classic Menu Item 1"', $fallback->post_content );
+
+		// Assert that fallback post_content contains the expected menu item url.
+		$this->assertStringContainsString( '"url":"/classic-menu-item-1"', $fallback->post_content );
+
+		// Cleanup.
+		wp_delete_nav_menu( $menu_id );
+	}
+
+	public function test_should_skip_if_filter_returns_truthy() {
 		add_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 
 		$actual = gutenberg_block_core_navigation_create_fallback();
 
+		// Asserr no fallback is created.
 		$this->assertEquals( $actual, null );
 
 		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );

From a139d85d0d0f568b779764336e8a05785b96157b Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 15:14:27 +0000
Subject: [PATCH 05/37] Refactor assertions to expected actual format

---
 phpunit/navigation-block-fallback-test.php | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index ae821ef92dd78c..83294caad36b20 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -30,14 +30,7 @@ public static function wpTearDownAfterClass() {
 		}
 	}
 
-	public function test_creates_fallback_navigation_with_page_list_by_default() {
-		$fallback = gutenberg_block_core_navigation_create_fallback();
 
-		$this->assertEquals( $fallback->post_type, 'wp_navigation' );
-		$this->assertEquals( $fallback->post_title, 'Navigation' );
-		$this->assertEquals( $fallback->post_content, '<!-- wp:page-list /-->' );
-		$this->assertEquals( $fallback->post_status, 'publish' );
-	}
 
 	public function test_gets_fallback_navigation_with_existing_navigation_menu_if_found() {
 
@@ -90,6 +83,15 @@ public function test_gets_fallback_navigation_with_existing_classic_menu_if_foun
 		wp_delete_nav_menu( $menu_id );
 	}
 
+	public function test_creates_fallback_navigation_with_page_list_by_default() {
+		$fallback = gutenberg_block_core_navigation_create_fallback();
+
+		$this->assertEquals( 'wp_navigation', $fallback->post_type );
+		$this->assertEquals( 'Navigation', $fallback->post_title, );
+		$this->assertEquals( '<!-- wp:page-list /-->', $fallback->post_content );
+		$this->assertEquals( 'publish', $fallback->post_status );
+	}
+
 	public function test_should_skip_if_filter_returns_truthy() {
 		add_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 

From 5e254c134ab74d4e4e7fdc1c0fcfed0a568328c4 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 15:16:50 +0000
Subject: [PATCH 06/37] Cleanup test file

---
 phpunit/navigation-block-fallback-test.php | 32 ++++------------------
 1 file changed, 6 insertions(+), 26 deletions(-)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index 83294caad36b20..39a46b60fb3ada 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -7,34 +7,14 @@
 
 class Tests_Block_Navigation_Fallbacks extends WP_UnitTestCase {
 
-	/**
-	 * @var WP_Post
-	 */
-	protected static $navigation_post;
-
-
-
-
 	public function set_up() {
 		parent::set_up();
 		switch_theme( 'emptytheme' );
 	}
 
-	public static function wpSetUpBeforeClass() {
-
-	}
-
-	public static function wpTearDownAfterClass() {
-		if ( ! empty( self::$post_with_comments_disabled->ID ) ) {
-			wp_delete_post( self::$navigation_post->ID, true );
-		}
-	}
-
-
-
 	public function test_gets_fallback_navigation_with_existing_navigation_menu_if_found() {
 
-		self::$navigation_post = self::factory()->post->create_and_get(
+		$navigation_post = self::factory()->post->create_and_get(
 			array(
 				'post_type'    => 'wp_navigation',
 				'post_title'   => 'Existing Navigation Menu',
@@ -44,10 +24,10 @@ public function test_gets_fallback_navigation_with_existing_navigation_menu_if_f
 
 		$fallback = gutenberg_block_core_navigation_create_fallback();
 
-		$this->assertEquals( $fallback->post_title, self::$navigation_post->post_title );
-		$this->assertEquals( $fallback->post_type, self::$navigation_post->post_type );
-		$this->assertEquals( $fallback->post_content, self::$navigation_post->post_content );
-		$this->assertEquals( $fallback->post_status, self::$navigation_post->post_status );
+		$this->assertEquals( $fallback->post_title, $navigation_post->post_title );
+		$this->assertEquals( $fallback->post_type, $navigation_post->post_type );
+		$this->assertEquals( $fallback->post_content, $navigation_post->post_content );
+		$this->assertEquals( $fallback->post_status, $navigation_post->post_status );
 	}
 
 	public function test_gets_fallback_navigation_with_existing_classic_menu_if_found() {
@@ -97,7 +77,7 @@ public function test_should_skip_if_filter_returns_truthy() {
 
 		$actual = gutenberg_block_core_navigation_create_fallback();
 
-		// Asserr no fallback is created.
+		// Assert no fallback is created.
 		$this->assertEquals( $actual, null );
 
 		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );

From 238d956026ac053957d93ef43923b1536841c4f0 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 15:22:45 +0000
Subject: [PATCH 07/37] Add checks for total Navigation Posts created

---
 phpunit/navigation-block-fallback-test.php | 48 +++++++++++++++++++---
 1 file changed, 42 insertions(+), 6 deletions(-)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index 39a46b60fb3ada..729a8162c8b479 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -12,22 +12,49 @@ public function set_up() {
 		switch_theme( 'emptytheme' );
 	}
 
+	public function get_navigations_in_database() {
+		$navs_in_db = new WP_Query(
+			array(
+				'post_type'      => 'wp_navigation',
+				'post_status'    => 'publish',
+				'posts_per_page' => -1,
+				'orderby'        => 'date',
+				'order'          => 'DESC',
+			)
+		);
+
+		return $navs_in_db->posts ?? array();
+	}
+
 	public function test_gets_fallback_navigation_with_existing_navigation_menu_if_found() {
 
-		$navigation_post = self::factory()->post->create_and_get(
+		$navigation_post_1 = self::factory()->post->create_and_get(
 			array(
 				'post_type'    => 'wp_navigation',
-				'post_title'   => 'Existing Navigation Menu',
+				'post_title'   => 'Existing Navigation Menu 1',
 				'post_content' => '<!-- wp:page-list /-->',
 			)
 		);
 
+		$navigation_post_2 = self::factory()->post->create_and_get(
+			array(
+				'post_type'    => 'wp_navigation',
+				'post_title'   => 'Existing Navigation Menu 2',
+				'post_content' => '<!-- wp:page-list /-->',
+			)
+		);
+
+		$most_recently_published_nav = $navigation_post_2;
+
 		$fallback = gutenberg_block_core_navigation_create_fallback();
 
-		$this->assertEquals( $fallback->post_title, $navigation_post->post_title );
-		$this->assertEquals( $fallback->post_type, $navigation_post->post_type );
-		$this->assertEquals( $fallback->post_content, $navigation_post->post_content );
-		$this->assertEquals( $fallback->post_status, $navigation_post->post_status );
+		$this->assertEquals( $fallback->post_title, $most_recently_published_nav->post_title );
+		$this->assertEquals( $fallback->post_type, $most_recently_published_nav->post_type );
+		$this->assertEquals( $fallback->post_content, $most_recently_published_nav->post_content );
+		$this->assertEquals( $fallback->post_status, $most_recently_published_nav->post_status );
+
+		$navs_in_db = $this->get_navigations_in_database();
+		$this->assertCount( 2, $navs_in_db );
 	}
 
 	public function test_gets_fallback_navigation_with_existing_classic_menu_if_found() {
@@ -59,6 +86,9 @@ public function test_gets_fallback_navigation_with_existing_classic_menu_if_foun
 		// Assert that fallback post_content contains the expected menu item url.
 		$this->assertStringContainsString( '"url":"/classic-menu-item-1"', $fallback->post_content );
 
+		$navs_in_db = $this->get_navigations_in_database();
+		$this->assertCount( 1, $navs_in_db );
+
 		// Cleanup.
 		wp_delete_nav_menu( $menu_id );
 	}
@@ -70,6 +100,9 @@ public function test_creates_fallback_navigation_with_page_list_by_default() {
 		$this->assertEquals( 'Navigation', $fallback->post_title, );
 		$this->assertEquals( '<!-- wp:page-list /-->', $fallback->post_content );
 		$this->assertEquals( 'publish', $fallback->post_status );
+
+		$navs_in_db = $this->get_navigations_in_database();
+		$this->assertCount( 1, $navs_in_db );
 	}
 
 	public function test_should_skip_if_filter_returns_truthy() {
@@ -80,6 +113,9 @@ public function test_should_skip_if_filter_returns_truthy() {
 		// Assert no fallback is created.
 		$this->assertEquals( $actual, null );
 
+		$navs_in_db = $this->get_navigations_in_database();
+		$this->assertCount( 0, $navs_in_db );
+
 		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 	}
 }

From ef16a4ce7e245927b500b2502daabeb85cda4bcb Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 15:26:48 +0000
Subject: [PATCH 08/37] Add test to cover prefering existing Nav Menu over
 Classic Menu

---
 phpunit/navigation-block-fallback-test.php | 28 ++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index 729a8162c8b479..fbbabb372c35d7 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -105,6 +105,34 @@ public function test_creates_fallback_navigation_with_page_list_by_default() {
 		$this->assertCount( 1, $navs_in_db );
 	}
 
+	public function test_creates_fallback_from_existing_navigation_menu_even_if_classic_menu_exists() {
+
+		// Create a Navigation Post
+		$navigation_post = self::factory()->post->create_and_get(
+			array(
+				'post_type'    => 'wp_navigation',
+				'post_title'   => 'Existing Navigation Menu',
+				'post_content' => '<!-- wp:page-list /-->',
+			)
+		);
+
+		// Also create a Classic Menu - this should be ignored.
+		$menu_id = wp_create_nav_menu( 'Existing Classic Menu' );
+
+		$fallback = gutenberg_block_core_navigation_create_fallback();
+
+		$this->assertEquals( $fallback->post_title, $navigation_post->post_title );
+		$this->assertEquals( $fallback->post_type, $navigation_post->post_type );
+		$this->assertEquals( $fallback->post_content, $navigation_post->post_content );
+		$this->assertEquals( $fallback->post_status, $navigation_post->post_status );
+
+		$navs_in_db = $this->get_navigations_in_database();
+		$this->assertCount( 1, $navs_in_db );
+
+		// Cleanup.
+		wp_delete_nav_menu( $menu_id );
+	}
+
 	public function test_should_skip_if_filter_returns_truthy() {
 		add_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 

From 4c8f78d5a7c716283cdbc751109eef343afcfd5e Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 15:31:38 +0000
Subject: [PATCH 09/37] Rename and improve function comment

---
 packages/block-library/src/navigation/index.php | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index 82fc92d1758e48..a453fc9f9668bb 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -436,11 +436,12 @@ function block_core_navigation_block_contains_core_navigation( $inner_blocks ) {
 }
 
 /**
- * Create and returns a navigation menu containing a page-list as a fallback.
+ * Create and returns a navigation menu containing default fallback content.
+ * (ideally a page-list).
  *
  * @return array the newly created navigation menu.
  */
-function block_core_navigation_get_default_pages_fallback() {
+function block_core_navigation_get_default_fallback() {
 	$registry = WP_Block_Type_Registry::get_instance();
 
 	// If `core/page-list` is not registered then use empty blocks.
@@ -486,7 +487,7 @@ function block_core_navigation_create_fallback() {
 
 	// If there are no navigation posts then default to a list of Pages.
 	if ( ! $navigation_post ) {
-		$navigation_post = block_core_navigation_get_default_pages_fallback();
+		$navigation_post = block_core_navigation_get_default_fallback();
 	}
 
 	return $navigation_post;

From fc8991d90182d9fce730a28d3d2ed6e6222f7d73 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 15:57:19 +0000
Subject: [PATCH 10/37] Add tests for retrieving fallback blocks

---
 phpunit/navigation-block-fallback-test.php | 80 ++++++++++++++++++++++
 1 file changed, 80 insertions(+)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index fbbabb372c35d7..a7bc0ecd0967d6 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -146,6 +146,86 @@ public function test_should_skip_if_filter_returns_truthy() {
 
 		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 	}
+
+	public function test_should_return_empty_fallback_blocks_when_no_navigations_exist() {
+		$fallback_blocks = gutenberg_block_core_navigation_get_fallback_blocks();
+
+		$this->assertIsArray( $fallback_blocks );
+		$this->assertEmpty( $fallback_blocks );
+	}
+
+	public function test_should_return_blocks_from_most_recently_created_navigation() {
+
+		$navigation_post_1 = self::factory()->post->create_and_get(
+			array(
+				'post_type'    => 'wp_navigation',
+				'post_title'   => 'Existing Navigation Menu 1',
+				'post_content' => '<!-- wp:page-list /-->',
+			)
+		);
+
+		$navigation_post_2 = self::factory()->post->create_and_get(
+			array(
+				'post_type'    => 'wp_navigation',
+				'post_title'   => 'Existing Navigation Menu 2',
+				'post_content' => '<!-- wp:navigation-link {"label":"Hello world","type":"post","id":1,"url":"/hello-world","kind":"post-type"} /-->',
+			)
+		);
+
+		$most_recently_published_nav = $navigation_post_2;
+
+		$fallback_blocks = gutenberg_block_core_navigation_get_fallback_blocks();
+
+		$block = $fallback_blocks[0];
+
+		// Check blocks match most recently Navigation Post data.
+		$this->assertEquals( $block['blockName'], 'core/navigation-link' );
+		$this->assertEquals( $block['attrs']['label'], 'Hello world' );
+		$this->assertEquals( $block['attrs']['url'], '/hello-world' );
+
+	}
+
+	public function test_should_return_empty_array_if_most_recently_created_navigation_is_empty() {
+
+		$navigation_post_2 = self::factory()->post->create_and_get(
+			array(
+				'post_type'    => 'wp_navigation',
+				'post_title'   => 'Existing Navigation Menu',
+				'post_content' => '', // empty.
+			)
+		);
+
+		$fallback_blocks = gutenberg_block_core_navigation_get_fallback_blocks();
+
+		$this->assertIsArray( $fallback_blocks );
+		$this->assertEmpty( $fallback_blocks );
+	}
+
+	public function test_should_return_filtered_blocks_fallback_is_filtered() {
+
+		function use_site_logo() {
+			return parse_blocks( '<!-- wp:site-logo /-->' );
+		}
+
+		add_filter( 'block_core_navigation_render_fallback', 'use_site_logo' );
+
+		$navigation_post_2 = self::factory()->post->create_and_get(
+			array(
+				'post_type'    => 'wp_navigation',
+				'post_title'   => 'Existing Navigation Menu',
+				'post_content' => '<!-- wp:navigation-link {"label":"Hello world","type":"post","id":1,"url":"/hello-world","kind":"post-type"} /-->',
+			)
+		);
+
+		$fallback_blocks = gutenberg_block_core_navigation_get_fallback_blocks();
+
+		$block = $fallback_blocks[0];
+
+		// Check blocks match most recently Navigation Post data.
+		$this->assertEquals( $block['blockName'], 'core/site-logo' );
+
+		remove_filter( 'block_core_navigation_render_fallback', 'use_site_logo' );
+	}
 }
 
 

From ff1258223644a5f7b623f4262ea12f5716ac3564 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 15:59:28 +0000
Subject: [PATCH 11/37] Ensure different post_content for different menus

---
 phpunit/navigation-block-fallback-test.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index a7bc0ecd0967d6..e3ab3538cc5db3 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -40,7 +40,7 @@ public function test_gets_fallback_navigation_with_existing_navigation_menu_if_f
 			array(
 				'post_type'    => 'wp_navigation',
 				'post_title'   => 'Existing Navigation Menu 2',
-				'post_content' => '<!-- wp:page-list /-->',
+				'post_content' => '<!-- wp:navigation-link {"label":"Hello world","type":"post","id":1,"url":"/hello-world","kind":"post-type"} /-->',
 			)
 		);
 

From c20ec7bba446a22de4631701c5dbcd3fc000c8e1 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 16:14:26 +0000
Subject: [PATCH 12/37] Test filtering empty blocks

---
 phpunit/navigation-block-fallback-test.php | 30 ++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index e3ab3538cc5db3..b5cbff0cea9d16 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -201,6 +201,36 @@ public function test_should_return_empty_array_if_most_recently_created_navigati
 		$this->assertEmpty( $fallback_blocks );
 	}
 
+	public function test_should_filter_out_empty_blocks_from_fallbacks() {
+
+		$navigation_post = self::factory()->post->create_and_get(
+			array(
+				'post_type'    => 'wp_navigation',
+				'post_title'   => 'Existing Navigation Menu',
+				'post_content' => '    <!-- wp:page-list /-->         ',
+			)
+		);
+
+		$fallback_blocks = gutenberg_block_core_navigation_get_fallback_blocks();
+
+		$first_block = $fallback_blocks[0];
+
+		// There should only be a single page list block and no "null" blocks.
+		$this->assertCount( 1, $fallback_blocks );
+		$this->assertEquals( $first_block['blockName'], 'core/page-list' );
+
+		// Check that no "empty" blocks exist with a blockName of 'null'.
+		// If the block parser encounters whitespace it will return a block with a blockName of null.
+		// This is an intentional feature, but is undesirable for our fallbacks.
+		$null_blocks = array_filter(
+			$fallback_blocks,
+			function( $block ) {
+				return $block['blockName'] === null;
+			}
+		);
+		$this->assertEmpty( $null_blocks );
+	}
+
 	public function test_should_return_filtered_blocks_fallback_is_filtered() {
 
 		function use_site_logo() {

From 1138e30aebff79d0b7a64f9542258d98a6009757 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 16:44:49 +0000
Subject: [PATCH 13/37] Fix parse error in unit tests

---
 phpunit/navigation-block-fallback-test.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index b5cbff0cea9d16..58c7cc35bef14c 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -74,7 +74,7 @@ public function test_gets_fallback_navigation_with_existing_classic_menu_if_foun
 		$fallback = gutenberg_block_core_navigation_create_fallback();
 
 		$this->assertEquals( 'Existing Classic Menu', $fallback->post_title, );
-		$this->assertEquals( 'wp_navigation', $fallback->post_type, );
+		$this->assertEquals( 'wp_navigation', $fallback->post_type );
 		$this->assertEquals( 'publish', $fallback->post_status );
 
 		// Assert that the fallback contains a navigation-link block.

From 1a82aafd41a2fdac034bb4aaa6cf61da754cd537 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 16:47:00 +0000
Subject: [PATCH 14/37] Fix PHP CS warnings

---
 phpunit/navigation-block-fallback-test.php | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index 58c7cc35bef14c..7ca8ab69d40c04 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -28,7 +28,7 @@ public function get_navigations_in_database() {
 
 	public function test_gets_fallback_navigation_with_existing_navigation_menu_if_found() {
 
-		$navigation_post_1 = self::factory()->post->create_and_get(
+		self::factory()->post->create_and_get(
 			array(
 				'post_type'    => 'wp_navigation',
 				'post_title'   => 'Existing Navigation Menu 1',
@@ -36,7 +36,7 @@ public function test_gets_fallback_navigation_with_existing_navigation_menu_if_f
 			)
 		);
 
-		$navigation_post_2 = self::factory()->post->create_and_get(
+		$most_recently_published_nav = self::factory()->post->create_and_get(
 			array(
 				'post_type'    => 'wp_navigation',
 				'post_title'   => 'Existing Navigation Menu 2',
@@ -44,8 +44,6 @@ public function test_gets_fallback_navigation_with_existing_navigation_menu_if_f
 			)
 		);
 
-		$most_recently_published_nav = $navigation_post_2;
-
 		$fallback = gutenberg_block_core_navigation_create_fallback();
 
 		$this->assertEquals( $fallback->post_title, $most_recently_published_nav->post_title );
@@ -107,7 +105,7 @@ public function test_creates_fallback_navigation_with_page_list_by_default() {
 
 	public function test_creates_fallback_from_existing_navigation_menu_even_if_classic_menu_exists() {
 
-		// Create a Navigation Post
+		// Create a Navigation Post.
 		$navigation_post = self::factory()->post->create_and_get(
 			array(
 				'post_type'    => 'wp_navigation',
@@ -156,7 +154,7 @@ public function test_should_return_empty_fallback_blocks_when_no_navigations_exi
 
 	public function test_should_return_blocks_from_most_recently_created_navigation() {
 
-		$navigation_post_1 = self::factory()->post->create_and_get(
+		self::factory()->post->create_and_get(
 			array(
 				'post_type'    => 'wp_navigation',
 				'post_title'   => 'Existing Navigation Menu 1',
@@ -164,7 +162,7 @@ public function test_should_return_blocks_from_most_recently_created_navigation(
 			)
 		);
 
-		$navigation_post_2 = self::factory()->post->create_and_get(
+		$most_recently_published_nav = self::factory()->post->create_and_get(
 			array(
 				'post_type'    => 'wp_navigation',
 				'post_title'   => 'Existing Navigation Menu 2',
@@ -172,8 +170,6 @@ public function test_should_return_blocks_from_most_recently_created_navigation(
 			)
 		);
 
-		$most_recently_published_nav = $navigation_post_2;
-
 		$fallback_blocks = gutenberg_block_core_navigation_get_fallback_blocks();
 
 		$block = $fallback_blocks[0];
@@ -187,7 +183,7 @@ public function test_should_return_blocks_from_most_recently_created_navigation(
 
 	public function test_should_return_empty_array_if_most_recently_created_navigation_is_empty() {
 
-		$navigation_post_2 = self::factory()->post->create_and_get(
+		self::factory()->post->create_and_get(
 			array(
 				'post_type'    => 'wp_navigation',
 				'post_title'   => 'Existing Navigation Menu',
@@ -239,7 +235,7 @@ function use_site_logo() {
 
 		add_filter( 'block_core_navigation_render_fallback', 'use_site_logo' );
 
-		$navigation_post_2 = self::factory()->post->create_and_get(
+		self::factory()->post->create_and_get(
 			array(
 				'post_type'    => 'wp_navigation',
 				'post_title'   => 'Existing Navigation Menu',

From a31eec487e961fcfeda1cee463853c55e796b1c3 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Wed, 1 Mar 2023 18:20:32 +0000
Subject: [PATCH 15/37] Fix more PHPCS warnings

---
 phpunit/navigation-block-fallback-test.php | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index 7ca8ab69d40c04..2a5c47544b92f9 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -23,7 +23,7 @@ public function get_navigations_in_database() {
 			)
 		);
 
-		return $navs_in_db->posts ?? array();
+		return $navs_in_db->posts ? $navs_in_db->posts : array();
 	}
 
 	public function test_gets_fallback_navigation_with_existing_navigation_menu_if_found() {
@@ -71,7 +71,7 @@ public function test_gets_fallback_navigation_with_existing_classic_menu_if_foun
 
 		$fallback = gutenberg_block_core_navigation_create_fallback();
 
-		$this->assertEquals( 'Existing Classic Menu', $fallback->post_title, );
+		$this->assertEquals( 'Existing Classic Menu', $fallback->post_title );
 		$this->assertEquals( 'wp_navigation', $fallback->post_type );
 		$this->assertEquals( 'publish', $fallback->post_status );
 

From ec6d2ad4d3def62954d9e58b23d437fb19eba609 Mon Sep 17 00:00:00 2001
From: scruffian <ben@scruffian.com>
Date: Thu, 2 Mar 2023 09:24:24 +0000
Subject: [PATCH 16/37] fix linting issues'

---
 packages/block-library/src/navigation/index.php |  4 ----
 phpunit/navigation-block-fallback-test.php      | 11 +++++++----
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index a453fc9f9668bb..e59a11b11c8b88 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -344,7 +344,6 @@ function block_core_navigation_maybe_use_classic_menu_fallback() {
 		return;
 	}
 
-
 	// Create a new navigation menu from the classic menu.
 	$wp_insert_post_result = wp_insert_post(
 		array(
@@ -357,9 +356,6 @@ function block_core_navigation_maybe_use_classic_menu_fallback() {
 		true // So that we can check whether the result is an error.
 	);
 
-
-
-
 	if ( is_wp_error( $wp_insert_post_result ) ) {
 		return;
 	}
diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index 2a5c47544b92f9..d845cede188a78 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -95,7 +95,7 @@ public function test_creates_fallback_navigation_with_page_list_by_default() {
 		$fallback = gutenberg_block_core_navigation_create_fallback();
 
 		$this->assertEquals( 'wp_navigation', $fallback->post_type );
-		$this->assertEquals( 'Navigation', $fallback->post_title, );
+		$this->assertEquals( 'Navigation', $fallback->post_title );
 		$this->assertEquals( '<!-- wp:page-list /-->', $fallback->post_content );
 		$this->assertEquals( 'publish', $fallback->post_status );
 
@@ -154,6 +154,7 @@ public function test_should_return_empty_fallback_blocks_when_no_navigations_exi
 
 	public function test_should_return_blocks_from_most_recently_created_navigation() {
 
+		// Create a fallback navigation.
 		self::factory()->post->create_and_get(
 			array(
 				'post_type'    => 'wp_navigation',
@@ -162,7 +163,8 @@ public function test_should_return_blocks_from_most_recently_created_navigation(
 			)
 		);
 
-		$most_recently_published_nav = self::factory()->post->create_and_get(
+		// Create another fallback navigation.
+		self::factory()->post->create_and_get(
 			array(
 				'post_type'    => 'wp_navigation',
 				'post_title'   => 'Existing Navigation Menu 2',
@@ -199,7 +201,8 @@ public function test_should_return_empty_array_if_most_recently_created_navigati
 
 	public function test_should_filter_out_empty_blocks_from_fallbacks() {
 
-		$navigation_post = self::factory()->post->create_and_get(
+		// Create a fallback navigation.
+		self::factory()->post->create_and_get(
 			array(
 				'post_type'    => 'wp_navigation',
 				'post_title'   => 'Existing Navigation Menu',
@@ -221,7 +224,7 @@ public function test_should_filter_out_empty_blocks_from_fallbacks() {
 		$null_blocks = array_filter(
 			$fallback_blocks,
 			function( $block ) {
-				return $block['blockName'] === null;
+				return null === $block['blockName'];
 			}
 		);
 		$this->assertEmpty( $null_blocks );

From 5665b743c671b2a97b5df383d0c2d4858098842b Mon Sep 17 00:00:00 2001
From: scruffian <ben@scruffian.com>
Date: Thu, 2 Mar 2023 16:53:55 +0000
Subject: [PATCH 17/37] change the hooks we create the fallback on

---
 packages/block-library/src/navigation/index.php | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index e59a11b11c8b88..e21aba816b36bb 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -572,6 +572,9 @@ function block_core_navigation_from_block_get_post_ids( $block ) {
  * @return string Returns the post content with the legacy widget added.
  */
 function render_block_core_navigation( $attributes, $content, $block ) {
+	// First things first, let's create the fallback.
+	block_core_navigation_create_fallback();
+
 	static $seen_menu_names = array();
 
 	// Flag used to indicate whether the rendered output is considered to be
@@ -917,6 +920,5 @@ function block_core_navigation_typographic_presets_backcompatibility( $parsed_bl
 
 add_filter( 'render_block_data', 'block_core_navigation_typographic_presets_backcompatibility' );
 
-// We have to aply this action on both init and admin init, as the code loads after init when in wp-admin.
-add_action( 'init', 'block_core_navigation_create_fallback' );
-add_action( 'admin_init', 'block_core_navigation_create_fallback' );
+// We apply this action on render_block_data, so that we generate a navigation in the dashboard.
+add_action( 'render_block_data', 'block_core_navigation_create_fallback' );

From e13b4f379f8627362795eda83f4b244bac6d6306 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Fri, 3 Mar 2023 10:25:07 +0000
Subject: [PATCH 18/37] Move hooks to run on one time operations and ensure
 only run for block themes

---
 packages/block-library/src/navigation/index.php | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index e21aba816b36bb..ed601b84f6da8f 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -472,6 +472,11 @@ function block_core_navigation_create_fallback() {
 		return;
 	}
 
+	// Don't create a fallback if the theme is not a block theme.
+	if ( ! wp_is_block_theme() ) {
+		return;
+	}
+
 	// Get the most recently published Navigation post.
 	$navigation_post = block_core_navigation_get_most_recently_published_navigation();
 
@@ -488,6 +493,9 @@ function block_core_navigation_create_fallback() {
 
 	return $navigation_post;
 }
+// Run on switching Theme and when installing WP for the first time.
+add_action( 'switch_theme', 'block_core_navigation_create_fallback' );
+add_action( 'wp_install', 'block_core_navigation_create_fallback' );
 
 
 /**
@@ -572,8 +580,6 @@ function block_core_navigation_from_block_get_post_ids( $block ) {
  * @return string Returns the post content with the legacy widget added.
  */
 function render_block_core_navigation( $attributes, $content, $block ) {
-	// First things first, let's create the fallback.
-	block_core_navigation_create_fallback();
 
 	static $seen_menu_names = array();
 
@@ -920,5 +926,5 @@ function block_core_navigation_typographic_presets_backcompatibility( $parsed_bl
 
 add_filter( 'render_block_data', 'block_core_navigation_typographic_presets_backcompatibility' );
 
-// We apply this action on render_block_data, so that we generate a navigation in the dashboard.
-add_action( 'render_block_data', 'block_core_navigation_create_fallback' );
+
+

From da7f46d2f28441543881c52537ce6373773f239b Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Fri, 3 Mar 2023 10:36:06 +0000
Subject: [PATCH 19/37] Fix tests

---
 phpunit/navigation-block-fallback-test.php | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index d845cede188a78..47935c086bf7a5 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -9,7 +9,13 @@ class Tests_Block_Navigation_Fallbacks extends WP_UnitTestCase {
 
 	public function set_up() {
 		parent::set_up();
+		// Navigation menu will be created on Theme switch. Therefore in order to test
+		// the behaviour of `gutenberg_block_core_navigation_create_fallback`
+		// the auto-creation of a fallback must be disabled for this initial
+		// theme switch.
+		add_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 		switch_theme( 'emptytheme' );
+		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 	}
 
 	public function get_navigations_in_database() {

From a5a36514b8406254e3b38bffb19e64e6db87221e Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Fri, 3 Mar 2023 10:40:44 +0000
Subject: [PATCH 20/37] Add tests for theme switch hook auto-creation

---
 phpunit/navigation-block-fallback-test.php | 40 +++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index 47935c086bf7a5..29c23e08019865 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -18,7 +18,7 @@ public function set_up() {
 		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 	}
 
-	public function get_navigations_in_database() {
+	private function get_navigations_in_database() {
 		$navs_in_db = new WP_Query(
 			array(
 				'post_type'      => 'wp_navigation',
@@ -32,6 +32,42 @@ public function get_navigations_in_database() {
 		return $navs_in_db->posts ? $navs_in_db->posts : array();
 	}
 
+	public function test_should_auto_create_navigation_menu_on_theme_switch() {
+		// Remove any existing disabling filters.
+		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );
+
+		// Should trigger creation of Navigation Menu if one does not already exist.
+		switch_theme( 'emptytheme' );
+
+		$navs_in_db = $this->get_navigations_in_database();
+		$this->assertCount( 1, $navs_in_db );
+	}
+
+	public function test_should_not_auto_create_navigation_menu_on_theme_switch_if_one_already_exists() {
+
+		self::factory()->post->create_and_get(
+			array(
+				'post_type'    => 'wp_navigation',
+				'post_title'   => 'Existing Navigation Menu',
+				'post_content' => '<!-- wp:navigation-link {"label":"Hello world","type":"post","id":1,"url":"/hello-world","kind":"post-type"} /-->',
+			)
+		);
+
+		// Remove any existing disabling filters.
+		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );
+
+		// Should trigger creation of Navigation Menu if one does not already exist.
+		switch_theme( 'emptytheme' );
+
+		$navs_in_db = $this->get_navigations_in_database();
+
+		// There should still only be one Navigation Menu.
+		$this->assertCount( 1, $navs_in_db );
+
+		// The existing Navigation Menu should be unchanged.
+		$this->assertEquals( 'Existing Navigation Menu', $navs_in_db[0]->post_title );
+	}
+
 	public function test_gets_fallback_navigation_with_existing_navigation_menu_if_found() {
 
 		self::factory()->post->create_and_get(
@@ -261,6 +297,8 @@ function use_site_logo() {
 
 		remove_filter( 'block_core_navigation_render_fallback', 'use_site_logo' );
 	}
+
+
 }
 
 

From 84bd74628a3ff0caea1056eb26ff744a0c8ffe91 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Fri, 3 Mar 2023 10:56:26 +0000
Subject: [PATCH 21/37] Check that there are no menus before Theme switch test

---
 phpunit/navigation-block-fallback-test.php | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index 29c23e08019865..49e0ac74f2e680 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -36,6 +36,9 @@ public function test_should_auto_create_navigation_menu_on_theme_switch() {
 		// Remove any existing disabling filters.
 		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 
+		$navs_in_db = $this->get_navigations_in_database();
+		$this->assertCount( 0, $navs_in_db );
+
 		// Should trigger creation of Navigation Menu if one does not already exist.
 		switch_theme( 'emptytheme' );
 
@@ -45,6 +48,7 @@ public function test_should_auto_create_navigation_menu_on_theme_switch() {
 
 	public function test_should_not_auto_create_navigation_menu_on_theme_switch_if_one_already_exists() {
 
+		// Pre-add a Navigation Menu to simulate when a user already has a menu.
 		self::factory()->post->create_and_get(
 			array(
 				'post_type'    => 'wp_navigation',

From f6dab81c8b7de774ee50d302a23b816d8ad475f8 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 09:48:01 +0000
Subject: [PATCH 22/37] Add test for wp_install

---
 phpunit/navigation-block-fallback-test.php | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index 49e0ac74f2e680..d58a736a577d0a 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -32,6 +32,18 @@ private function get_navigations_in_database() {
 		return $navs_in_db->posts ? $navs_in_db->posts : array();
 	}
 
+	private function mock_wp_install() {
+		$user = get_current_user();
+		do_action( 'wp_install', $user );
+	}
+
+	public function test_should_auto_create_navigation_menu_on_wp_install() {
+		$this->mock_wp_install();
+
+		$navs_in_db = $this->get_navigations_in_database();
+		$this->assertCount( 1, $navs_in_db );
+	}
+
 	public function test_should_auto_create_navigation_menu_on_theme_switch() {
 		// Remove any existing disabling filters.
 		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );

From 641a0ed23884a637998ec21fe0075abeab333115 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 09:51:13 +0000
Subject: [PATCH 23/37] Update comment to indicate page list is not an ideal
 scenario

---
 packages/block-library/src/navigation/index.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index ed601b84f6da8f..af1ad0b42848ad 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -433,7 +433,7 @@ function block_core_navigation_block_contains_core_navigation( $inner_blocks ) {
 
 /**
  * Create and returns a navigation menu containing default fallback content.
- * (ideally a page-list).
+ * (a page-list if registered).
  *
  * @return array the newly created navigation menu.
  */

From 02c135399f26d395fe7b1c201e7668e78f81ed7f Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 11:50:18 +0000
Subject: [PATCH 24/37] Add test to validate menus not created when switching
 to a block Theme

---
 phpunit/navigation-block-fallback-test.php | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index d58a736a577d0a..377247ff8777a4 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -58,6 +58,18 @@ public function test_should_auto_create_navigation_menu_on_theme_switch() {
 		$this->assertCount( 1, $navs_in_db );
 	}
 
+	public function test_should_not_auto_create_navigation_menu_on_theme_switch_to_classic_theme() {
+
+		$navs_in_db = $this->get_navigations_in_database();
+		$this->assertCount( 0, $navs_in_db );
+
+		// Should trigger creation of Navigation Menu if one does not already exist.
+		switch_theme( 'twentytwenty' );
+
+		$navs_in_db = $this->get_navigations_in_database();
+		$this->assertCount( 0, $navs_in_db );
+	}
+
 	public function test_should_not_auto_create_navigation_menu_on_theme_switch_if_one_already_exists() {
 
 		// Pre-add a Navigation Menu to simulate when a user already has a menu.

From 11ab9db0c23c2922323ea948fc9caf13508fb7ee Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 11:59:12 +0000
Subject: [PATCH 25/37] Revert whitespace changes

Co-authored-by: Dave Smith <444434+getdave@users.noreply.github.com>
---
 packages/block-library/src/navigation/index.php | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index af1ad0b42848ad..050d0735743e6d 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -580,7 +580,6 @@ function block_core_navigation_from_block_get_post_ids( $block ) {
  * @return string Returns the post content with the legacy widget added.
  */
 function render_block_core_navigation( $attributes, $content, $block ) {
-
 	static $seen_menu_names = array();
 
 	// Flag used to indicate whether the rendered output is considered to be
@@ -925,6 +924,3 @@ function block_core_navigation_typographic_presets_backcompatibility( $parsed_bl
 }
 
 add_filter( 'render_block_data', 'block_core_navigation_typographic_presets_backcompatibility' );
-
-
-

From 3a64b4d5256a346a4a5ea34141ca53e24cba11b5 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 14:34:18 +0000
Subject: [PATCH 26/37] Apply PHPUnit annotations from review

Co-authored-by: Anton Vlasenko <43744263+anton-vlasenko@users.noreply.github.com>
---
 phpunit/navigation-block-fallback-test.php | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index 377247ff8777a4..cb943e9dcc54a5 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -37,6 +37,9 @@ private function mock_wp_install() {
 		do_action( 'wp_install', $user );
 	}
 
+	/**
+	 * @covers ::block_core_navigation_get_default_fallback
+	 */
 	public function test_should_auto_create_navigation_menu_on_wp_install() {
 		$this->mock_wp_install();
 
@@ -49,13 +52,13 @@ public function test_should_auto_create_navigation_menu_on_theme_switch() {
 		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 
 		$navs_in_db = $this->get_navigations_in_database();
-		$this->assertCount( 0, $navs_in_db );
+		$this->assertCount( 0, $navs_in_db, 'Navigation Menu should not exist before running the tests.' );
 
 		// Should trigger creation of Navigation Menu if one does not already exist.
 		switch_theme( 'emptytheme' );
 
 		$navs_in_db = $this->get_navigations_in_database();
-		$this->assertCount( 1, $navs_in_db );
+		$this->assertCount( 1, $navs_in_db, 'No Navigation Menu was found.' );
 	}
 
 	public function test_should_not_auto_create_navigation_menu_on_theme_switch_to_classic_theme() {

From d59cde34936547d2c4e9738234c8a3ec09feeea6 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 14:40:00 +0000
Subject: [PATCH 27/37] Remove unnecessary return and annotation function

---
 packages/block-library/src/navigation/index.php | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index 050d0735743e6d..a1567bcb6818fb 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -464,7 +464,17 @@ function block_core_navigation_get_default_fallback() {
 }
 
 /**
- * Creates the appropriate fallback to be used on the front of the site.
+ * Creates an appropriate fallback Navigation Menu (`wp_navigation` Post)
+ * to be used by the Navigation block.
+ *
+ * Behaviour:
+ * 1. If there is a Navigation menu already then use it.
+ * 2. If there is a Classic menu then convert it to a Navigation menu.
+ * 3. If there is no Navigation menu and no Classic menu then create a default menu.
+ *
+ * The fallback menu is only created if the theme is a block theme.
+ *
+ * @return void
  */
 function block_core_navigation_create_fallback() {
 	$should_skip = apply_filters( 'block_core_navigation_skip_fallback', false );
@@ -490,8 +500,6 @@ function block_core_navigation_create_fallback() {
 	if ( ! $navigation_post ) {
 		$navigation_post = block_core_navigation_get_default_fallback();
 	}
-
-	return $navigation_post;
 }
 // Run on switching Theme and when installing WP for the first time.
 add_action( 'switch_theme', 'block_core_navigation_create_fallback' );

From a9c724869f790cb0f9e4ff8f382bdf868e765eb5 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 14:58:13 +0000
Subject: [PATCH 28/37] Try adding messages to all assertions

---
 phpunit/navigation-block-fallback-test.php | 81 ++++++++++------------
 1 file changed, 38 insertions(+), 43 deletions(-)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index cb943e9dcc54a5..10c9e424883ff3 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -44,7 +44,7 @@ public function test_should_auto_create_navigation_menu_on_wp_install() {
 		$this->mock_wp_install();
 
 		$navs_in_db = $this->get_navigations_in_database();
-		$this->assertCount( 1, $navs_in_db );
+		$this->assertCount( 1, $navs_in_db, 'No Navigation Menu was found.' );
 	}
 
 	public function test_should_auto_create_navigation_menu_on_theme_switch() {
@@ -52,7 +52,7 @@ public function test_should_auto_create_navigation_menu_on_theme_switch() {
 		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 
 		$navs_in_db = $this->get_navigations_in_database();
-		$this->assertCount( 0, $navs_in_db, 'Navigation Menu should not exist before running the tests.' );
+		$this->assertCount( 0, $navs_in_db, 'Navigation Menu should not exist before switching Theme.' );
 
 		// Should trigger creation of Navigation Menu if one does not already exist.
 		switch_theme( 'emptytheme' );
@@ -64,13 +64,13 @@ public function test_should_auto_create_navigation_menu_on_theme_switch() {
 	public function test_should_not_auto_create_navigation_menu_on_theme_switch_to_classic_theme() {
 
 		$navs_in_db = $this->get_navigations_in_database();
-		$this->assertCount( 0, $navs_in_db );
+		$this->assertCount( 0, $navs_in_db, 'Navigation Menu should not exist before switching Theme.' );
 
 		// Should trigger creation of Navigation Menu if one does not already exist.
 		switch_theme( 'twentytwenty' );
 
 		$navs_in_db = $this->get_navigations_in_database();
-		$this->assertCount( 0, $navs_in_db );
+		$this->assertCount( 0, $navs_in_db, 'A Navigation Menu should not exist.' );
 	}
 
 	public function test_should_not_auto_create_navigation_menu_on_theme_switch_if_one_already_exists() {
@@ -93,10 +93,10 @@ public function test_should_not_auto_create_navigation_menu_on_theme_switch_if_o
 		$navs_in_db = $this->get_navigations_in_database();
 
 		// There should still only be one Navigation Menu.
-		$this->assertCount( 1, $navs_in_db );
+		$this->assertCount( 1, $navs_in_db, 'A single Navigation Menu should exist.' );
 
 		// The existing Navigation Menu should be unchanged.
-		$this->assertEquals( 'Existing Navigation Menu', $navs_in_db[0]->post_title );
+		$this->assertEquals( 'Existing Navigation Menu', $navs_in_db[0]->post_title, 'The title of the Navigation Menu should match the existing Navigation Menu' );
 	}
 
 	public function test_gets_fallback_navigation_with_existing_navigation_menu_if_found() {
@@ -119,13 +119,13 @@ public function test_gets_fallback_navigation_with_existing_navigation_menu_if_f
 
 		$fallback = gutenberg_block_core_navigation_create_fallback();
 
-		$this->assertEquals( $fallback->post_title, $most_recently_published_nav->post_title );
-		$this->assertEquals( $fallback->post_type, $most_recently_published_nav->post_type );
-		$this->assertEquals( $fallback->post_content, $most_recently_published_nav->post_content );
-		$this->assertEquals( $fallback->post_status, $most_recently_published_nav->post_status );
+		$this->assertEquals( $fallback->post_title, $most_recently_published_nav->post_title, 'The title of the fallback Navigation Menu should match the title of the most recently published Navigation Menu.' );
+		$this->assertEquals( $fallback->post_type, $most_recently_published_nav->post_type, 'The post type of the fallback Navigation Menu should match the post type of the most recently published Navigation Menu.' );
+		$this->assertEquals( $fallback->post_content, $most_recently_published_nav->post_content, 'The contents of the fallback Navigation Menu should match the contents of the most recently published Navigation Menu.' );
+		$this->assertEquals( $fallback->post_status, $most_recently_published_nav->post_status, 'The status of the fallback Navigation Menu should match the status of the most recently published Navigation Menu.' );
 
 		$navs_in_db = $this->get_navigations_in_database();
-		$this->assertCount( 2, $navs_in_db );
+		$this->assertCount( 2, $navs_in_db, '2 Navigation Menus should exist.' );
 	}
 
 	public function test_gets_fallback_navigation_with_existing_classic_menu_if_found() {
@@ -144,21 +144,19 @@ public function test_gets_fallback_navigation_with_existing_classic_menu_if_foun
 
 		$fallback = gutenberg_block_core_navigation_create_fallback();
 
-		$this->assertEquals( 'Existing Classic Menu', $fallback->post_title );
-		$this->assertEquals( 'wp_navigation', $fallback->post_type );
-		$this->assertEquals( 'publish', $fallback->post_status );
+		$this->assertEquals( 'Existing Classic Menu', $fallback->post_title, 'The title of the fallback Navigation Menu should match the name of the Classic menu.' );
 
 		// Assert that the fallback contains a navigation-link block.
-		$this->assertStringContainsString( '<!-- wp:navigation-link', $fallback->post_content );
+		$this->assertStringContainsString( '<!-- wp:navigation-link', $fallback->post_content, 'The fallback Navigation Menu should contain a `core/navigation-link` block.' );
 
 		// Assert that fallback post_content contains the expected menu item title.
-		$this->assertStringContainsString( '"label":"Classic Menu Item 1"', $fallback->post_content );
+		$this->assertStringContainsString( '"label":"Classic Menu Item 1"', $fallback->post_content, 'The fallback Navigation Menu should contain menu item with a label matching the title of the menu item from the Classic Menu.' );
 
 		// Assert that fallback post_content contains the expected menu item url.
-		$this->assertStringContainsString( '"url":"/classic-menu-item-1"', $fallback->post_content );
+		$this->assertStringContainsString( '"url":"/classic-menu-item-1"', $fallback->post_content, 'The fallback Navigation Menu should contain menu item with a url matching the slug of the menu item from the Classic Menu.' );
 
 		$navs_in_db = $this->get_navigations_in_database();
-		$this->assertCount( 1, $navs_in_db );
+		$this->assertCount( 1, $navs_in_db, 'A single Navigation Menu should exist.' );
 
 		// Cleanup.
 		wp_delete_nav_menu( $menu_id );
@@ -167,13 +165,13 @@ public function test_gets_fallback_navigation_with_existing_classic_menu_if_foun
 	public function test_creates_fallback_navigation_with_page_list_by_default() {
 		$fallback = gutenberg_block_core_navigation_create_fallback();
 
-		$this->assertEquals( 'wp_navigation', $fallback->post_type );
-		$this->assertEquals( 'Navigation', $fallback->post_title );
-		$this->assertEquals( '<!-- wp:page-list /-->', $fallback->post_content );
-		$this->assertEquals( 'publish', $fallback->post_status );
+		$this->assertEquals( 'wp_navigation', $fallback->post_type, 'The fallback Navigation Menu should be of the expected Post type.' );
+		$this->assertEquals( 'Navigation', $fallback->post_title, 'The fallback Navigation Menu should be have the expected title.' );
+		$this->assertEquals( '<!-- wp:page-list /-->', $fallback->post_content, 'The fallback Navigation Menu should contain a Page List block.' );
+		$this->assertEquals( 'publish', $fallback->post_status, 'The fallback Navigation Menu should be published.' );
 
 		$navs_in_db = $this->get_navigations_in_database();
-		$this->assertCount( 1, $navs_in_db );
+		$this->assertCount( 1, $navs_in_db, 'A single Navigation Menu should exist.' );
 	}
 
 	public function test_creates_fallback_from_existing_navigation_menu_even_if_classic_menu_exists() {
@@ -192,13 +190,13 @@ public function test_creates_fallback_from_existing_navigation_menu_even_if_clas
 
 		$fallback = gutenberg_block_core_navigation_create_fallback();
 
-		$this->assertEquals( $fallback->post_title, $navigation_post->post_title );
-		$this->assertEquals( $fallback->post_type, $navigation_post->post_type );
-		$this->assertEquals( $fallback->post_content, $navigation_post->post_content );
-		$this->assertEquals( $fallback->post_status, $navigation_post->post_status );
+		$this->assertEquals( $fallback->post_title, $navigation_post->post_title, 'The title of the fallback Navigation Menu should match that of the existing Navigation Menu.' );
+		$this->assertEquals( $fallback->post_type, $navigation_post->post_type, 'The post type of the fallback Navigation Menu should match that of the existing Navigation Menu.' );
+		$this->assertEquals( $fallback->post_content, $navigation_post->post_content, 'The contents of the fallback Navigation Menu should match that of the existing Navigation Menu.' );
+		$this->assertEquals( $fallback->post_status, $navigation_post->post_status, 'The status of the fallback Navigation Menu should match that of the existing Navigation Menu.' );
 
 		$navs_in_db = $this->get_navigations_in_database();
-		$this->assertCount( 1, $navs_in_db );
+		$this->assertCount( 1, $navs_in_db, 'A single Navigation Menu should exist.' );
 
 		// Cleanup.
 		wp_delete_nav_menu( $menu_id );
@@ -209,11 +207,8 @@ public function test_should_skip_if_filter_returns_truthy() {
 
 		$actual = gutenberg_block_core_navigation_create_fallback();
 
-		// Assert no fallback is created.
-		$this->assertEquals( $actual, null );
-
 		$navs_in_db = $this->get_navigations_in_database();
-		$this->assertCount( 0, $navs_in_db );
+		$this->assertCount( 0, $navs_in_db, 'No Navigation Menus should have been created.' );
 
 		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 	}
@@ -221,8 +216,8 @@ public function test_should_skip_if_filter_returns_truthy() {
 	public function test_should_return_empty_fallback_blocks_when_no_navigations_exist() {
 		$fallback_blocks = gutenberg_block_core_navigation_get_fallback_blocks();
 
-		$this->assertIsArray( $fallback_blocks );
-		$this->assertEmpty( $fallback_blocks );
+		$this->assertIsArray( $fallback_blocks, 'Fallback blocks should be an array.' );
+		$this->assertEmpty( $fallback_blocks, 'Fallback blocks should be empty.' );
 	}
 
 	public function test_should_return_blocks_from_most_recently_created_navigation() {
@@ -250,9 +245,9 @@ public function test_should_return_blocks_from_most_recently_created_navigation(
 		$block = $fallback_blocks[0];
 
 		// Check blocks match most recently Navigation Post data.
-		$this->assertEquals( $block['blockName'], 'core/navigation-link' );
-		$this->assertEquals( $block['attrs']['label'], 'Hello world' );
-		$this->assertEquals( $block['attrs']['url'], '/hello-world' );
+		$this->assertEquals( $block['blockName'], 'core/navigation-link', '1st fallback block should match expected type.' );
+		$this->assertEquals( $block['attrs']['label'], 'Hello world', '1st fallback block\'s label should match.' );
+		$this->assertEquals( $block['attrs']['url'], '/hello-world', '1st fallback block\'s url should match.' );
 
 	}
 
@@ -268,8 +263,8 @@ public function test_should_return_empty_array_if_most_recently_created_navigati
 
 		$fallback_blocks = gutenberg_block_core_navigation_get_fallback_blocks();
 
-		$this->assertIsArray( $fallback_blocks );
-		$this->assertEmpty( $fallback_blocks );
+		$this->assertIsArray( $fallback_blocks, 'Fallback blocks should be an array.' );
+		$this->assertEmpty( $fallback_blocks, 'Fallback blocks should be empty.' );
 	}
 
 	public function test_should_filter_out_empty_blocks_from_fallbacks() {
@@ -288,8 +283,8 @@ public function test_should_filter_out_empty_blocks_from_fallbacks() {
 		$first_block = $fallback_blocks[0];
 
 		// There should only be a single page list block and no "null" blocks.
-		$this->assertCount( 1, $fallback_blocks );
-		$this->assertEquals( $first_block['blockName'], 'core/page-list' );
+		$this->assertCount( 1, $fallback_blocks, 'Fallback blocks should contain a single block.' );
+		$this->assertEquals( $first_block['blockName'], 'core/page-list', 'Fallback block should be a page list.' );
 
 		// Check that no "empty" blocks exist with a blockName of 'null'.
 		// If the block parser encounters whitespace it will return a block with a blockName of null.
@@ -300,7 +295,7 @@ function( $block ) {
 				return null === $block['blockName'];
 			}
 		);
-		$this->assertEmpty( $null_blocks );
+		$this->assertEmpty( $null_blocks, 'Fallback blocks should not contain any null blocks.' );
 	}
 
 	public function test_should_return_filtered_blocks_fallback_is_filtered() {
@@ -324,7 +319,7 @@ function use_site_logo() {
 		$block = $fallback_blocks[0];
 
 		// Check blocks match most recently Navigation Post data.
-		$this->assertEquals( $block['blockName'], 'core/site-logo' );
+		$this->assertEquals( $block['blockName'], 'core/site-logo', '1st fallback block should match expected type.' );
 
 		remove_filter( 'block_core_navigation_render_fallback', 'use_site_logo' );
 	}

From e0d8d7ccf7b35c3590c72e5d2111fa7ec84a6394 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 15:02:49 +0000
Subject: [PATCH 29/37] Add @covers annotation

---
 phpunit/navigation-block-fallback-test.php | 56 ++++++++++++++++++----
 1 file changed, 47 insertions(+), 9 deletions(-)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index 10c9e424883ff3..a3ba654a8af975 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -38,7 +38,7 @@ private function mock_wp_install() {
 	}
 
 	/**
-	 * @covers ::block_core_navigation_get_default_fallback
+	 * @covers ::block_core_navigation_create_fallback
 	 */
 	public function test_should_auto_create_navigation_menu_on_wp_install() {
 		$this->mock_wp_install();
@@ -47,6 +47,9 @@ public function test_should_auto_create_navigation_menu_on_wp_install() {
 		$this->assertCount( 1, $navs_in_db, 'No Navigation Menu was found.' );
 	}
 
+	/**
+	 * @covers ::block_core_navigation_create_fallback
+	 */
 	public function test_should_auto_create_navigation_menu_on_theme_switch() {
 		// Remove any existing disabling filters.
 		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );
@@ -61,6 +64,9 @@ public function test_should_auto_create_navigation_menu_on_theme_switch() {
 		$this->assertCount( 1, $navs_in_db, 'No Navigation Menu was found.' );
 	}
 
+	/**
+	 * @covers ::block_core_navigation_create_fallback
+	 */
 	public function test_should_not_auto_create_navigation_menu_on_theme_switch_to_classic_theme() {
 
 		$navs_in_db = $this->get_navigations_in_database();
@@ -73,6 +79,9 @@ public function test_should_not_auto_create_navigation_menu_on_theme_switch_to_c
 		$this->assertCount( 0, $navs_in_db, 'A Navigation Menu should not exist.' );
 	}
 
+	/**
+	 * @covers ::block_core_navigation_create_fallback
+	 */
 	public function test_should_not_auto_create_navigation_menu_on_theme_switch_if_one_already_exists() {
 
 		// Pre-add a Navigation Menu to simulate when a user already has a menu.
@@ -99,7 +108,10 @@ public function test_should_not_auto_create_navigation_menu_on_theme_switch_if_o
 		$this->assertEquals( 'Existing Navigation Menu', $navs_in_db[0]->post_title, 'The title of the Navigation Menu should match the existing Navigation Menu' );
 	}
 
-	public function test_gets_fallback_navigation_with_existing_navigation_menu_if_found() {
+	/**
+	 * @covers ::block_core_navigation_create_fallback
+	 */
+	public function test_creates_fallback_navigation_with_existing_navigation_menu_if_found() {
 
 		self::factory()->post->create_and_get(
 			array(
@@ -128,7 +140,10 @@ public function test_gets_fallback_navigation_with_existing_navigation_menu_if_f
 		$this->assertCount( 2, $navs_in_db, '2 Navigation Menus should exist.' );
 	}
 
-	public function test_gets_fallback_navigation_with_existing_classic_menu_if_found() {
+	/**
+	 * @covers ::block_core_navigation_create_fallback
+	 */
+	public function test_creates_fallback_navigation_with_existing_classic_menu_if_found() {
 
 		$menu_id = wp_create_nav_menu( 'Existing Classic Menu' );
 
@@ -162,6 +177,9 @@ public function test_gets_fallback_navigation_with_existing_classic_menu_if_foun
 		wp_delete_nav_menu( $menu_id );
 	}
 
+	/**
+	 * @covers ::block_core_navigation_create_fallback
+	 */
 	public function test_creates_fallback_navigation_with_page_list_by_default() {
 		$fallback = gutenberg_block_core_navigation_create_fallback();
 
@@ -174,6 +192,9 @@ public function test_creates_fallback_navigation_with_page_list_by_default() {
 		$this->assertCount( 1, $navs_in_db, 'A single Navigation Menu should exist.' );
 	}
 
+	/**
+	 * @covers ::block_core_navigation_create_fallback
+	 */
 	public function test_creates_fallback_from_existing_navigation_menu_even_if_classic_menu_exists() {
 
 		// Create a Navigation Post.
@@ -202,6 +223,9 @@ public function test_creates_fallback_from_existing_navigation_menu_even_if_clas
 		wp_delete_nav_menu( $menu_id );
 	}
 
+	/**
+	 * @covers ::block_core_navigation_create_fallback
+	 */
 	public function test_should_skip_if_filter_returns_truthy() {
 		add_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 
@@ -213,14 +237,21 @@ public function test_should_skip_if_filter_returns_truthy() {
 		remove_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 	}
 
-	public function test_should_return_empty_fallback_blocks_when_no_navigations_exist() {
+
+	/**
+	 * @covers ::gutenberg_block_core_navigation_get_fallback_blocks
+	 */
+	public function test_should_get_fallback_blocks_when_no_navigations_exist() {
 		$fallback_blocks = gutenberg_block_core_navigation_get_fallback_blocks();
 
 		$this->assertIsArray( $fallback_blocks, 'Fallback blocks should be an array.' );
 		$this->assertEmpty( $fallback_blocks, 'Fallback blocks should be empty.' );
 	}
 
-	public function test_should_return_blocks_from_most_recently_created_navigation() {
+	/**
+	 * @covers ::gutenberg_block_core_navigation_get_fallback_blocks
+	 */
+	public function test_should_get_blocks_from_most_recently_created_navigation() {
 
 		// Create a fallback navigation.
 		self::factory()->post->create_and_get(
@@ -251,7 +282,10 @@ public function test_should_return_blocks_from_most_recently_created_navigation(
 
 	}
 
-	public function test_should_return_empty_array_if_most_recently_created_navigation_is_empty() {
+	/**
+	 * @covers ::gutenberg_block_core_navigation_get_fallback_blocks
+	 */
+	public function test_should_get_empty_array_if_most_recently_created_navigation_is_empty() {
 
 		self::factory()->post->create_and_get(
 			array(
@@ -267,6 +301,9 @@ public function test_should_return_empty_array_if_most_recently_created_navigati
 		$this->assertEmpty( $fallback_blocks, 'Fallback blocks should be empty.' );
 	}
 
+	/**
+	 * @covers ::gutenberg_block_core_navigation_get_fallback_blocks
+	 */
 	public function test_should_filter_out_empty_blocks_from_fallbacks() {
 
 		// Create a fallback navigation.
@@ -298,7 +335,10 @@ function( $block ) {
 		$this->assertEmpty( $null_blocks, 'Fallback blocks should not contain any null blocks.' );
 	}
 
-	public function test_should_return_filtered_blocks_fallback_is_filtered() {
+	/**
+	 * @covers ::gutenberg_block_core_navigation_get_fallback_blocks
+	 */
+	public function test_should_get_filtered_blocks_if_fallback_is_filtered() {
 
 		function use_site_logo() {
 			return parse_blocks( '<!-- wp:site-logo /-->' );
@@ -323,8 +363,6 @@ function use_site_logo() {
 
 		remove_filter( 'block_core_navigation_render_fallback', 'use_site_logo' );
 	}
-
-
 }
 
 

From dff16827dea0ff6f77e8dd2d3e31dea9229b6ce4 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 15:11:21 +0000
Subject: [PATCH 30/37] Apply correct annotations to test class

---
 phpunit/navigation-block-fallback-test.php | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/navigation-block-fallback-test.php
index a3ba654a8af975..402e2e48ea5867 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/navigation-block-fallback-test.php
@@ -2,7 +2,8 @@
 /**
  * Tests Fallback Behavior for Navigation block
  *
- * @package WordPress
+ * @package    Gutenberg
+ * @subpackage block-library
  */
 
 class Tests_Block_Navigation_Fallbacks extends WP_UnitTestCase {

From 8604f516ed063ef33c71b182ffe9ab147d0b806b Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 15:14:07 +0000
Subject: [PATCH 31/37] Rename test file and add group annotation

---
 ...t.php => class-block-library-navigation-fallbacks-test.php} | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
 rename phpunit/{navigation-block-fallback-test.php => class-block-library-navigation-fallbacks-test.php} (99%)

diff --git a/phpunit/navigation-block-fallback-test.php b/phpunit/class-block-library-navigation-fallbacks-test.php
similarity index 99%
rename from phpunit/navigation-block-fallback-test.php
rename to phpunit/class-block-library-navigation-fallbacks-test.php
index 402e2e48ea5867..733c85b49c55d4 100644
--- a/phpunit/navigation-block-fallback-test.php
+++ b/phpunit/class-block-library-navigation-fallbacks-test.php
@@ -4,9 +4,10 @@
  *
  * @package    Gutenberg
  * @subpackage block-library
+ * @group     Navigation block
  */
 
-class Tests_Block_Navigation_Fallbacks extends WP_UnitTestCase {
+class Block_Library_Navigation_Fallbacks_Test extends WP_UnitTestCase {
 
 	public function set_up() {
 		parent::set_up();

From 249fd749bcbe1a855ec5b559f93954d4ddf70df3 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 15:19:21 +0000
Subject: [PATCH 32/37] Fix PHPCS unused variable

---
 phpunit/class-block-library-navigation-fallbacks-test.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/phpunit/class-block-library-navigation-fallbacks-test.php b/phpunit/class-block-library-navigation-fallbacks-test.php
index 733c85b49c55d4..6870d7144997a1 100644
--- a/phpunit/class-block-library-navigation-fallbacks-test.php
+++ b/phpunit/class-block-library-navigation-fallbacks-test.php
@@ -231,7 +231,7 @@ public function test_creates_fallback_from_existing_navigation_menu_even_if_clas
 	public function test_should_skip_if_filter_returns_truthy() {
 		add_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 
-		$actual = gutenberg_block_core_navigation_create_fallback();
+		gutenberg_block_core_navigation_create_fallback();
 
 		$navs_in_db = $this->get_navigations_in_database();
 		$this->assertCount( 0, $navs_in_db, 'No Navigation Menus should have been created.' );

From 2b2795e386244a15ad95d927198830a4c66a994e Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 17:32:40 +0000
Subject: [PATCH 33/37] Normalise assertion

Co-authored-by: Anton Vlasenko <43744263+anton-vlasenko@users.noreply.github.com>
---
 phpunit/class-block-library-navigation-fallbacks-test.php | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/phpunit/class-block-library-navigation-fallbacks-test.php b/phpunit/class-block-library-navigation-fallbacks-test.php
index 6870d7144997a1..486ad9acf2eaff 100644
--- a/phpunit/class-block-library-navigation-fallbacks-test.php
+++ b/phpunit/class-block-library-navigation-fallbacks-test.php
@@ -246,8 +246,7 @@ public function test_should_skip_if_filter_returns_truthy() {
 	public function test_should_get_fallback_blocks_when_no_navigations_exist() {
 		$fallback_blocks = gutenberg_block_core_navigation_get_fallback_blocks();
 
-		$this->assertIsArray( $fallback_blocks, 'Fallback blocks should be an array.' );
-		$this->assertEmpty( $fallback_blocks, 'Fallback blocks should be empty.' );
+		$this->assertSame( array(), $fallback_blocks, 'Fallback blocks should be an empty array.' );
 	}
 
 	/**

From 61f9a8e659ef8e143c0bce96d54e208c76611c02 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 20:23:10 +0000
Subject: [PATCH 34/37] Fix tests

---
 .../block-library/src/navigation/index.php    | 31 ++++++++++++-------
 ...lock-library-navigation-fallbacks-test.php | 12 +++----
 2 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index a1567bcb6818fb..9936de9eaec451 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -476,8 +476,9 @@ function block_core_navigation_get_default_fallback() {
  *
  * @return void
  */
-function block_core_navigation_create_fallback() {
+function block_core_navigation_create_and_get_fallback() {
 	$should_skip = apply_filters( 'block_core_navigation_skip_fallback', false );
+
 	if ( $should_skip ) {
 		return;
 	}
@@ -487,23 +488,29 @@ function block_core_navigation_create_fallback() {
 		return;
 	}
 
-	// Get the most recently published Navigation post.
-	$navigation_post = block_core_navigation_get_most_recently_published_navigation();
+	// Get the most recently published Navigation menu.
+	$navigation_menu = block_core_navigation_get_most_recently_published_navigation();
 
-	// If there are no navigation posts then try to find a classic menu
-	// and convert it into a block based navigation menu.
-	if ( ! $navigation_post ) {
-		$navigation_post = block_core_navigation_maybe_use_classic_menu_fallback();
+	if ( $navigation_menu ) {
+		return $navigation_menu;
 	}
 
-	// If there are no navigation posts then default to a list of Pages.
-	if ( ! $navigation_post ) {
-		$navigation_post = block_core_navigation_get_default_fallback();
+	// If there are no Navigation menus then try to find a Classic menu
+	// and convert it into a Navigation menu.
+
+	$navigation_menu = block_core_navigation_maybe_use_classic_menu_fallback();
+
+	if ( $navigation_menu ) {
+		return $navigation_menu;
 	}
+
+	// If there are no navigation posts then default to a list of Pages.
+	return block_core_navigation_get_default_fallback();
+
 }
 // Run on switching Theme and when installing WP for the first time.
-add_action( 'switch_theme', 'block_core_navigation_create_fallback' );
-add_action( 'wp_install', 'block_core_navigation_create_fallback' );
+add_action( 'switch_theme', 'block_core_navigation_create_and_get_fallback' );
+add_action( 'wp_install', 'block_core_navigation_create_and_get_fallback' );
 
 
 /**
diff --git a/phpunit/class-block-library-navigation-fallbacks-test.php b/phpunit/class-block-library-navigation-fallbacks-test.php
index 486ad9acf2eaff..1bebfb6c7702ea 100644
--- a/phpunit/class-block-library-navigation-fallbacks-test.php
+++ b/phpunit/class-block-library-navigation-fallbacks-test.php
@@ -12,7 +12,7 @@ class Block_Library_Navigation_Fallbacks_Test extends WP_UnitTestCase {
 	public function set_up() {
 		parent::set_up();
 		// Navigation menu will be created on Theme switch. Therefore in order to test
-		// the behaviour of `gutenberg_block_core_navigation_create_fallback`
+		// the behaviour of `gutenberg_block_core_navigation_create_and_get_fallback`
 		// the auto-creation of a fallback must be disabled for this initial
 		// theme switch.
 		add_filter( 'block_core_navigation_skip_fallback', '__return_true' );
@@ -131,7 +131,7 @@ public function test_creates_fallback_navigation_with_existing_navigation_menu_i
 			)
 		);
 
-		$fallback = gutenberg_block_core_navigation_create_fallback();
+		$fallback = gutenberg_block_core_navigation_create_and_get_fallback();
 
 		$this->assertEquals( $fallback->post_title, $most_recently_published_nav->post_title, 'The title of the fallback Navigation Menu should match the title of the most recently published Navigation Menu.' );
 		$this->assertEquals( $fallback->post_type, $most_recently_published_nav->post_type, 'The post type of the fallback Navigation Menu should match the post type of the most recently published Navigation Menu.' );
@@ -159,7 +159,7 @@ public function test_creates_fallback_navigation_with_existing_classic_menu_if_f
 			)
 		);
 
-		$fallback = gutenberg_block_core_navigation_create_fallback();
+		$fallback = gutenberg_block_core_navigation_create_and_get_fallback();
 
 		$this->assertEquals( 'Existing Classic Menu', $fallback->post_title, 'The title of the fallback Navigation Menu should match the name of the Classic menu.' );
 
@@ -183,7 +183,7 @@ public function test_creates_fallback_navigation_with_existing_classic_menu_if_f
 	 * @covers ::block_core_navigation_create_fallback
 	 */
 	public function test_creates_fallback_navigation_with_page_list_by_default() {
-		$fallback = gutenberg_block_core_navigation_create_fallback();
+		$fallback = gutenberg_block_core_navigation_create_and_get_fallback();
 
 		$this->assertEquals( 'wp_navigation', $fallback->post_type, 'The fallback Navigation Menu should be of the expected Post type.' );
 		$this->assertEquals( 'Navigation', $fallback->post_title, 'The fallback Navigation Menu should be have the expected title.' );
@@ -211,7 +211,7 @@ public function test_creates_fallback_from_existing_navigation_menu_even_if_clas
 		// Also create a Classic Menu - this should be ignored.
 		$menu_id = wp_create_nav_menu( 'Existing Classic Menu' );
 
-		$fallback = gutenberg_block_core_navigation_create_fallback();
+		$fallback = gutenberg_block_core_navigation_create_and_get_fallback();
 
 		$this->assertEquals( $fallback->post_title, $navigation_post->post_title, 'The title of the fallback Navigation Menu should match that of the existing Navigation Menu.' );
 		$this->assertEquals( $fallback->post_type, $navigation_post->post_type, 'The post type of the fallback Navigation Menu should match that of the existing Navigation Menu.' );
@@ -231,7 +231,7 @@ public function test_creates_fallback_from_existing_navigation_menu_even_if_clas
 	public function test_should_skip_if_filter_returns_truthy() {
 		add_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 
-		gutenberg_block_core_navigation_create_fallback();
+		gutenberg_block_core_navigation_create_and_get_fallback();
 
 		$navs_in_db = $this->get_navigations_in_database();
 		$this->assertCount( 0, $navs_in_db, 'No Navigation Menus should have been created.' );

From 0c8bbe227a05d47e23ed15a8ecb888715d9e523b Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 20:29:47 +0000
Subject: [PATCH 35/37] Refactor to avoid requiring a return value from the
 hooked creation function

---
 .../block-library/src/navigation/index.php    | 13 ++++++------
 ...lock-library-navigation-fallbacks-test.php | 20 +++++++++++++------
 2 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index 9936de9eaec451..585477cfb667a0 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -476,7 +476,7 @@ function block_core_navigation_get_default_fallback() {
  *
  * @return void
  */
-function block_core_navigation_create_and_get_fallback() {
+function block_core_navigation_create_fallback() {
 	$should_skip = apply_filters( 'block_core_navigation_skip_fallback', false );
 
 	if ( $should_skip ) {
@@ -492,7 +492,7 @@ function block_core_navigation_create_and_get_fallback() {
 	$navigation_menu = block_core_navigation_get_most_recently_published_navigation();
 
 	if ( $navigation_menu ) {
-		return $navigation_menu;
+		return;
 	}
 
 	// If there are no Navigation menus then try to find a Classic menu
@@ -501,16 +501,15 @@ function block_core_navigation_create_and_get_fallback() {
 	$navigation_menu = block_core_navigation_maybe_use_classic_menu_fallback();
 
 	if ( $navigation_menu ) {
-		return $navigation_menu;
+		return;
 	}
 
 	// If there are no navigation posts then default to a list of Pages.
-	return block_core_navigation_get_default_fallback();
-
+	block_core_navigation_get_default_fallback();
 }
 // Run on switching Theme and when installing WP for the first time.
-add_action( 'switch_theme', 'block_core_navigation_create_and_get_fallback' );
-add_action( 'wp_install', 'block_core_navigation_create_and_get_fallback' );
+add_action( 'switch_theme', 'block_core_navigation_create_fallback' );
+add_action( 'wp_install', 'block_core_navigation_create_fallback' );
 
 
 /**
diff --git a/phpunit/class-block-library-navigation-fallbacks-test.php b/phpunit/class-block-library-navigation-fallbacks-test.php
index 1bebfb6c7702ea..8568ac967daf65 100644
--- a/phpunit/class-block-library-navigation-fallbacks-test.php
+++ b/phpunit/class-block-library-navigation-fallbacks-test.php
@@ -12,7 +12,7 @@ class Block_Library_Navigation_Fallbacks_Test extends WP_UnitTestCase {
 	public function set_up() {
 		parent::set_up();
 		// Navigation menu will be created on Theme switch. Therefore in order to test
-		// the behaviour of `gutenberg_block_core_navigation_create_and_get_fallback`
+		// the behaviour of `gutenberg_block_core_navigation_create_fallback`
 		// the auto-creation of a fallback must be disabled for this initial
 		// theme switch.
 		add_filter( 'block_core_navigation_skip_fallback', '__return_true' );
@@ -131,7 +131,9 @@ public function test_creates_fallback_navigation_with_existing_navigation_menu_i
 			)
 		);
 
-		$fallback = gutenberg_block_core_navigation_create_and_get_fallback();
+		gutenberg_block_core_navigation_create_fallback();
+
+		$fallback = $this->get_navigations_in_database()[0];
 
 		$this->assertEquals( $fallback->post_title, $most_recently_published_nav->post_title, 'The title of the fallback Navigation Menu should match the title of the most recently published Navigation Menu.' );
 		$this->assertEquals( $fallback->post_type, $most_recently_published_nav->post_type, 'The post type of the fallback Navigation Menu should match the post type of the most recently published Navigation Menu.' );
@@ -159,7 +161,9 @@ public function test_creates_fallback_navigation_with_existing_classic_menu_if_f
 			)
 		);
 
-		$fallback = gutenberg_block_core_navigation_create_and_get_fallback();
+		gutenberg_block_core_navigation_create_fallback();
+
+		$fallback = $this->get_navigations_in_database()[0];
 
 		$this->assertEquals( 'Existing Classic Menu', $fallback->post_title, 'The title of the fallback Navigation Menu should match the name of the Classic menu.' );
 
@@ -183,7 +187,9 @@ public function test_creates_fallback_navigation_with_existing_classic_menu_if_f
 	 * @covers ::block_core_navigation_create_fallback
 	 */
 	public function test_creates_fallback_navigation_with_page_list_by_default() {
-		$fallback = gutenberg_block_core_navigation_create_and_get_fallback();
+		gutenberg_block_core_navigation_create_fallback();
+
+		$fallback = $this->get_navigations_in_database()[0];
 
 		$this->assertEquals( 'wp_navigation', $fallback->post_type, 'The fallback Navigation Menu should be of the expected Post type.' );
 		$this->assertEquals( 'Navigation', $fallback->post_title, 'The fallback Navigation Menu should be have the expected title.' );
@@ -211,7 +217,9 @@ public function test_creates_fallback_from_existing_navigation_menu_even_if_clas
 		// Also create a Classic Menu - this should be ignored.
 		$menu_id = wp_create_nav_menu( 'Existing Classic Menu' );
 
-		$fallback = gutenberg_block_core_navigation_create_and_get_fallback();
+		gutenberg_block_core_navigation_create_fallback();
+
+		$fallback = $this->get_navigations_in_database()[0];
 
 		$this->assertEquals( $fallback->post_title, $navigation_post->post_title, 'The title of the fallback Navigation Menu should match that of the existing Navigation Menu.' );
 		$this->assertEquals( $fallback->post_type, $navigation_post->post_type, 'The post type of the fallback Navigation Menu should match that of the existing Navigation Menu.' );
@@ -231,7 +239,7 @@ public function test_creates_fallback_from_existing_navigation_menu_even_if_clas
 	public function test_should_skip_if_filter_returns_truthy() {
 		add_filter( 'block_core_navigation_skip_fallback', '__return_true' );
 
-		gutenberg_block_core_navigation_create_and_get_fallback();
+		gutenberg_block_core_navigation_create_fallback();
 
 		$navs_in_db = $this->get_navigations_in_database();
 		$this->assertCount( 0, $navs_in_db, 'No Navigation Menus should have been created.' );

From 3f164c799b7c548239304545c203990db9bdcb90 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 20:44:45 +0000
Subject: [PATCH 36/37] Refactor creation functions to SRP.

---
 .../block-library/src/navigation/index.php    | 48 +++++++++----------
 1 file changed, 23 insertions(+), 25 deletions(-)

diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index 585477cfb667a0..b51a4f279eb93d 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -329,22 +329,26 @@ function block_core_navigation_get_classic_menu_fallback_blocks( $classic_nav_me
  *
  * @return array the normalized parsed blocks.
  */
-function block_core_navigation_maybe_use_classic_menu_fallback() {
-	// See if we have a classic menu.
+function block_core_navigation_create_classic_menu_fallback() {
+	// See if we have a Classic menu.
 	$classic_nav_menu = block_core_navigation_get_classic_menu_fallback();
 
+	// Exit early if one does not exist.
 	if ( ! $classic_nav_menu ) {
-		return;
+		return new WP_Error( 'no_classic_menu', __( 'No classic menu exists to convert to a block.' ) );
 	}
 
-	// If we have a classic menu then convert it to blocks.
+	// If we have a Classic menu then convert it to blocks.
 	$classic_nav_menu_blocks = block_core_navigation_get_classic_menu_fallback_blocks( $classic_nav_menu );
 
+	// If it's empty then exit early.
 	if ( empty( $classic_nav_menu_blocks ) ) {
-		return;
+		return new WP_Error( 'no_classic_menu', __( 'Classic menu is empty or could not be converted to blocks.' ) );
 	}
 
-	// Create a new navigation menu from the classic menu.
+	$return_errors = true;
+
+	// Create a new Navigation menu from the Classic menu blocks.
 	$wp_insert_post_result = wp_insert_post(
 		array(
 			'post_content' => $classic_nav_menu_blocks,
@@ -353,15 +357,12 @@ function block_core_navigation_maybe_use_classic_menu_fallback() {
 			'post_status'  => 'publish',
 			'post_type'    => 'wp_navigation',
 		),
-		true // So that we can check whether the result is an error.
+		$return_errors // So that we can check whether the result is an error.
 	);
 
-	if ( is_wp_error( $wp_insert_post_result ) ) {
-		return;
-	}
 
-	// Fetch the most recently published navigation which will be the classic one created above.
-	return block_core_navigation_get_most_recently_published_navigation();
+	return $wp_insert_post_result;
+
 }
 
 /**
@@ -437,7 +438,7 @@ function block_core_navigation_block_contains_core_navigation( $inner_blocks ) {
  *
  * @return array the newly created navigation menu.
  */
-function block_core_navigation_get_default_fallback() {
+function block_core_navigation_create_default_fallback() {
 	$registry = WP_Block_Type_Registry::get_instance();
 
 	// If `core/page-list` is not registered then use empty blocks.
@@ -455,12 +456,7 @@ function block_core_navigation_get_default_fallback() {
 		true // So that we can check whether the result is an error.
 	);
 
-	if ( is_wp_error( $wp_insert_post_result ) ) {
-		return;
-	}
-
-	// Fetch the most recently published navigation which will be the default one created above.
-	return block_core_navigation_get_most_recently_published_navigation();
+	return $wp_insert_post_result;
 }
 
 /**
@@ -491,21 +487,23 @@ function block_core_navigation_create_fallback() {
 	// Get the most recently published Navigation menu.
 	$navigation_menu = block_core_navigation_get_most_recently_published_navigation();
 
+	// If there is already a Navigation menu then exit.
 	if ( $navigation_menu ) {
 		return;
 	}
 
 	// If there are no Navigation menus then try to find a Classic menu
-	// and convert it into a Navigation menu.
-
-	$navigation_menu = block_core_navigation_maybe_use_classic_menu_fallback();
+	// and attempt to convert it into a Navigation menu.
+	$navigation_menu = block_core_navigation_create_classic_menu_fallback();
 
-	if ( $navigation_menu ) {
+	// If the conversion + creation was successful then exit.
+	if ( ! is_wp_error( $navigation_menu ) ) {
 		return;
 	}
 
-	// If there are no navigation posts then default to a list of Pages.
-	block_core_navigation_get_default_fallback();
+	// If the Classic menu process did not result in a post
+	// then default to creating a default fallback Navigaiton menu.
+	block_core_navigation_create_default_fallback();
 }
 // Run on switching Theme and when installing WP for the first time.
 add_action( 'switch_theme', 'block_core_navigation_create_fallback' );

From 7722010e0a9aadb6d1afc34dbca595d21e6c7146 Mon Sep 17 00:00:00 2001
From: Dave Smith <getdavemail@gmail.com>
Date: Mon, 6 Mar 2023 20:50:49 +0000
Subject: [PATCH 37/37] Improve doc blocks

---
 .../block-library/src/navigation/index.php    | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/packages/block-library/src/navigation/index.php b/packages/block-library/src/navigation/index.php
index b51a4f279eb93d..f6facb0f72c71a 100644
--- a/packages/block-library/src/navigation/index.php
+++ b/packages/block-library/src/navigation/index.php
@@ -325,9 +325,10 @@ function block_core_navigation_get_classic_menu_fallback_blocks( $classic_nav_me
 }
 
 /**
- * If there's a the classic menu then use it as a fallback.
+ * Checks for a Classic Menu and attempts to convert into a block-based
+ * Navigation menu.
  *
- * @return array the normalized parsed blocks.
+ * @return int|WP_Error The Navigation menu post ID on success. A WP_Error on failure.
  */
 function block_core_navigation_create_classic_menu_fallback() {
 	// See if we have a Classic menu.
@@ -360,9 +361,7 @@ function block_core_navigation_create_classic_menu_fallback() {
 		$return_errors // So that we can check whether the result is an error.
 	);
 
-
 	return $wp_insert_post_result;
-
 }
 
 /**
@@ -433,10 +432,10 @@ function block_core_navigation_block_contains_core_navigation( $inner_blocks ) {
 }
 
 /**
- * Create and returns a navigation menu containing default fallback content.
+ * Creates a navigation menu containing default fallback content.
  * (a page-list if registered).
  *
- * @return array the newly created navigation menu.
+ * @return int|WP_Error The post ID on success. A WP_Error on failure.
  */
 function block_core_navigation_create_default_fallback() {
 	$registry = WP_Block_Type_Registry::get_instance();
@@ -485,19 +484,19 @@ function block_core_navigation_create_fallback() {
 	}
 
 	// Get the most recently published Navigation menu.
-	$navigation_menu = block_core_navigation_get_most_recently_published_navigation();
+	$existing_navigation_menu = block_core_navigation_get_most_recently_published_navigation();
 
 	// If there is already a Navigation menu then exit.
-	if ( $navigation_menu ) {
+	if ( $existing_navigation_menu ) {
 		return;
 	}
 
 	// If there are no Navigation menus then try to find a Classic menu
 	// and attempt to convert it into a Navigation menu.
-	$navigation_menu = block_core_navigation_create_classic_menu_fallback();
+	$converted_classic_menu_id = block_core_navigation_create_classic_menu_fallback();
 
 	// If the conversion + creation was successful then exit.
-	if ( ! is_wp_error( $navigation_menu ) ) {
+	if ( ! is_wp_error( $converted_classic_menu_id ) ) {
 		return;
 	}