diff --git a/.github/workflows/composer-diff.yml b/.github/workflows/composer-diff.yml
new file mode 100644
index 0000000..35e28dd
--- /dev/null
+++ b/.github/workflows/composer-diff.yml
@@ -0,0 +1,28 @@
+name: Composer Diff
+on:
+  pull_request:
+    paths:
+      - 'composer.lock'
+permissions:
+  contents: write
+  pull-requests: write
+jobs:
+  composer-diff:
+    name: Composer Diff
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: Generate composer diff
+        id: composer_diff
+        uses: IonBazan/composer-diff-action@v1
+      - uses: marocchino/sticky-pull-request-comment@v2
+        if: ${{ steps.composer_diff.outputs.composer_diff_exit_code != 0 }}
+        with:
+          header: composer-diff
+          message: |
+            <summary>Composer Changes</summary>
+
+            ${{ steps.composer_diff.outputs.composer_diff }}
diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 447e296..9fa8884 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -6,7 +6,7 @@ jobs:
         runs-on: ubuntu-latest
         steps:
             - name: Checkout
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
             - name: Lint
               run: |
                 composer install
diff --git a/.github/workflows/shellcheck.yml b/.github/workflows/shellcheck.yml
deleted file mode 100644
index 17025cf..0000000
--- a/.github/workflows/shellcheck.yml
+++ /dev/null
@@ -1,14 +0,0 @@
-name: Shellcheck
-on:
-  push:
-    paths:
-      - 'bin/*.sh'
-jobs:
-  shellcheck:
-    name: Shellcheck
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout code
-        uses: actions/checkout@v3
-      - name: Shellcheck
-        run: find bin/ -name "*.sh" | grep -v "install-wp-tests.sh" | xargs shellcheck
\ No newline at end of file
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 125d9e6..46d56ae 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: PHP Compatibility
         uses: pantheon-systems/phpcompatibility-action@dev
         with:
@@ -26,23 +26,35 @@ jobs:
     services:
       mariadb:
         image: mariadb:10.6
+    strategy:
+      matrix:
+        php_version: [7.4, 8.1, 8.3] # Versions represent newest 7.x, WP supported with exclusions, and beta support.
     steps:
-      - uses: actions/checkout@v3
-      - name: Setup PHP 8.3
+      - uses: actions/checkout@v4
+      - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: 8.3
+          php-version: ${{ matrix.php_version }}
           extensions: mysqli, zip, imagick
       - name: Start MySQL
         run: sudo systemctl start mysql
       - name: Cache dependencies
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: ~/vendor
           key: test-phpunit-dependencies-${{ hashFiles('composer.json') }}
           restore-keys: test-phpunit-dependencies-${{ hashFiles('composer.json') }}
       - name: Install Composer dependencies
-        run: composer install
+        run: |
+          if [ ${{ matrix.php_version }} = "7.4" ]; then
+            composer update
+          fi
+          composer install
+      - name: Install WP-CLI
+        run: |
+          curl -O https://raw.githubusercontent.com/wp-cli/builds/gh-pages/phar/wp-cli.phar
+          chmod +x wp-cli.phar
+          sudo mv wp-cli.phar /usr/local/bin/wp
       - name: Run PHPUnit
         run: bash ./bin/phpunit-test.sh
   
diff --git a/.gitignore b/.gitignore
index 9a4f997..26ab0af 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,9 @@
 # Ignore composer files.
 /vendor
-composer.lock
\ No newline at end of file
+composer.lock
+
+# Ignore bin files copied from wpunit-helpers
+/bin/install-local-tests.sh
+/bin/install-wp-tests.sh
+/bin/phpunit-test.sh
+/bin/helpers.sh
\ No newline at end of file
diff --git a/bin/install-local-tests.sh b/bin/install-local-tests.sh
deleted file mode 100755
index c1f8cc5..0000000
--- a/bin/install-local-tests.sh
+++ /dev/null
@@ -1,61 +0,0 @@
-#!/bin/bash
-set -e
-
-# Initialize variables with default values
-TMPDIR="/tmp"
-DB_NAME="wordpress_test"
-DB_USER="root"
-DB_PASS=""
-DB_HOST="127.0.0.1"
-WP_VERSION="latest"
-SKIP_DB=""
-
-# Display usage information
-usage() {
-  echo "Usage:"
-  echo "./install-local-tests.sh [--dbname=wordpress_test] [--dbuser=root] [--dbpass=''] [--dbhost=127.0.0.1] [--wpversion=latest] [--no-db]"
-}
-
-# Parse command-line arguments
-for i in "$@"
-do
-case $i in
-    --dbname=*)
-    DB_NAME="${i#*=}"
-    shift
-    ;;
-    --dbuser=*)
-    DB_USER="${i#*=}"
-    shift
-    ;;
-    --dbpass=*)
-    DB_PASS="${i#*=}"
-    shift
-    ;;
-    --dbhost=*)
-    DB_HOST="${i#*=}"
-    shift
-    ;;
-    --wpversion=*)
-    WP_VERSION="${i#*=}"
-    shift
-    ;;
-    --no-db)
-    SKIP_DB="true"
-    shift
-    ;;
-    *)
-    # unknown option
-    usage
-    exit 1
-    ;;
-esac
-done
-
-# Run install-wp-tests.sh
-echo "Installing local tests into ${TMPDIR}"
-bash "$(dirname "$0")/install-wp-tests.sh" "$DB_NAME" "$DB_USER" "$DB_PASS" "$DB_HOST" "$WP_VERSION" "$SKIP_DB"
-
-# Run PHPUnit
-echo "Running PHPUnit"
-composer phpunit
diff --git a/bin/install-wp-tests.sh b/bin/install-wp-tests.sh
deleted file mode 100755
index 675dd97..0000000
--- a/bin/install-wp-tests.sh
+++ /dev/null
@@ -1,151 +0,0 @@
-#!/usr/bin/env bash
-
-if [ $# -lt 3 ]; then
-	echo "usage: $0 <db-name> <db-user> <db-pass> [db-host] [wp-version] [skip-database-creation]"
-	exit 1
-fi
-
-DB_NAME=$1
-DB_USER=$2
-DB_PASS=$3
-DB_HOST=${4-localhost}
-WP_VERSION=${5-latest}
-SKIP_DB_CREATE=${6-false}
-
-TMPDIR=${TMPDIR-/tmp}
-WP_TESTS_DIR=${WP_TESTS_DIR-$TMPDIR/wordpress-tests-lib}
-WP_CORE_DIR=${WP_CORE_DIR-$TMPDIR/wordpress/}
-
-download() {
-    if [ `which curl` ]; then
-        curl -s "$1" > "$2";
-    elif [ `which wget` ]; then
-        wget -nv -O "$2" "$1"
-    fi
-}
-
-if [[ $WP_VERSION =~ ^[0-9]+\.[0-9]+$ ]]; then
-	WP_TESTS_TAG="branches/$WP_VERSION"
-elif [[ $WP_VERSION =~ [0-9]+\.[0-9]+\.[0-9]+ ]]; then
-	if [[ $WP_VERSION =~ [0-9]+\.[0-9]+\.[0] ]]; then
-		# version x.x.0 means the first release of the major version, so strip off the .0 and download version x.x
-		WP_TESTS_TAG="tags/${WP_VERSION%??}"
-	else
-		WP_TESTS_TAG="tags/$WP_VERSION"
-	fi
-elif [[ $WP_VERSION == 'nightly' || $WP_VERSION == 'trunk' ]]; then
-	WP_TESTS_TAG="trunk"
-else
-	# http serves a single offer, whereas https serves multiple. we only want one
-	download http://api.wordpress.org/core/version-check/1.7/ /tmp/wp-latest.json
-	grep '[0-9]+\.[0-9]+(\.[0-9]+)?' /tmp/wp-latest.json
-	LATEST_VERSION=$(grep -o '"version":"[^"]*' /tmp/wp-latest.json | sed 's/"version":"//')
-	if [[ -z "$LATEST_VERSION" ]]; then
-		echo "Latest WordPress version could not be found"
-		exit 1
-	fi
-	WP_TESTS_TAG="tags/$LATEST_VERSION"
-fi
-
-set -e
-
-install_wp() {
-
-	if [ -d $WP_CORE_DIR ]; then
-		return;
-	fi
-
-	mkdir -p $WP_CORE_DIR
-
-	if [[ $WP_VERSION == 'nightly' || $WP_VERSION == 'trunk' ]]; then
-		mkdir -p $TMPDIR/wordpress-nightly
-		download https://wordpress.org/nightly-builds/wordpress-latest.zip  $TMPDIR/wordpress-nightly/wordpress-nightly.zip
-		unzip -q $TMPDIR/wordpress-nightly/wordpress-nightly.zip -d $TMPDIR/wordpress-nightly/
-		mv $TMPDIR/wordpress-nightly/wordpress/* $WP_CORE_DIR
-	else
-		if [ $WP_VERSION == 'latest' ]; then
-			local ARCHIVE_NAME='latest'
-		elif [[ $WP_VERSION =~ [0-9]+\.[0-9]+ ]]; then
-			# https serves multiple offers, whereas http serves single.
-			download https://api.wordpress.org/core/version-check/1.7/ $TMPDIR/wp-latest.json
-			if [[ $WP_VERSION =~ [0-9]+\.[0-9]+\.[0] ]]; then
-				# version x.x.0 means the first release of the major version, so strip off the .0 and download version x.x
-				LATEST_VERSION=${WP_VERSION%??}
-			else
-				# otherwise, scan the releases and get the most up to date minor version of the major release
-				local VERSION_ESCAPED=`echo $WP_VERSION | sed 's/\./\\\\./g'`
-				LATEST_VERSION=$(grep -o '"version":"'$VERSION_ESCAPED'[^"]*' $TMPDIR/wp-latest.json | sed 's/"version":"//' | head -1)
-			fi
-			if [[ -z "$LATEST_VERSION" ]]; then
-				local ARCHIVE_NAME="wordpress-$WP_VERSION"
-			else
-				local ARCHIVE_NAME="wordpress-$LATEST_VERSION"
-			fi
-		else
-			local ARCHIVE_NAME="wordpress-$WP_VERSION"
-		fi
-		download https://wordpress.org/${ARCHIVE_NAME}.tar.gz  $TMPDIR/wordpress.tar.gz
-		tar --strip-components=1 -zxmf $TMPDIR/wordpress.tar.gz -C $WP_CORE_DIR
-	fi
-
-	download https://raw.github.com/markoheijnen/wp-mysqli/master/db.php $WP_CORE_DIR/wp-content/db.php
-}
-
-install_test_suite() {
-	# portable in-place argument for both GNU sed and Mac OSX sed
-	if [[ $(uname -s) == 'Darwin' ]]; then
-		local ioption='-i .bak'
-	else
-		local ioption='-i'
-	fi
-
-	# set up testing suite if it doesn't yet exist
-	if [ ! -d $WP_TESTS_DIR ]; then
-		# set up testing suite
-		mkdir -p $WP_TESTS_DIR
-		svn co --quiet --ignore-externals https://develop.svn.wordpress.org/${WP_TESTS_TAG}/tests/phpunit/includes/ $WP_TESTS_DIR/includes
-		svn co --quiet --ignore-externals https://develop.svn.wordpress.org/${WP_TESTS_TAG}/tests/phpunit/data/ $WP_TESTS_DIR/data
-	fi
-
-	if [ ! -f wp-tests-config.php ]; then
-		download https://develop.svn.wordpress.org/${WP_TESTS_TAG}/wp-tests-config-sample.php "$WP_TESTS_DIR"/wp-tests-config.php
-		# remove all forward slashes in the end
-		WP_CORE_DIR=$(echo $WP_CORE_DIR | sed "s:/\+$::")
-		sed $ioption "s:dirname( __FILE__ ) . '/src/':'$WP_CORE_DIR/':" "$WP_TESTS_DIR"/wp-tests-config.php
-		sed $ioption "s/youremptytestdbnamehere/$DB_NAME/" "$WP_TESTS_DIR"/wp-tests-config.php
-		sed $ioption "s/yourusernamehere/$DB_USER/" "$WP_TESTS_DIR"/wp-tests-config.php
-		sed $ioption "s/yourpasswordhere/$DB_PASS/" "$WP_TESTS_DIR"/wp-tests-config.php
-		sed $ioption "s|localhost|${DB_HOST}|" "$WP_TESTS_DIR"/wp-tests-config.php
-	fi
-
-}
-
-install_db() {
-
-	if [ ${SKIP_DB_CREATE} = "true" ]; then
-		return 0
-	fi
-
-	# parse DB_HOST for port or socket references
-	local PARTS=(${DB_HOST//\:/ })
-	local DB_HOSTNAME=${PARTS[0]};
-	local DB_SOCK_OR_PORT=${PARTS[1]};
-	local EXTRA=""
-
-	if ! [ -z $DB_HOSTNAME ] ; then
-		if [ $(echo $DB_SOCK_OR_PORT | grep -e '^[0-9]\{1,\}$') ]; then
-			EXTRA=" --host=$DB_HOSTNAME --port=$DB_SOCK_OR_PORT --protocol=tcp"
-		elif ! [ -z $DB_SOCK_OR_PORT ] ; then
-			EXTRA=" --socket=$DB_SOCK_OR_PORT"
-		elif ! [ -z $DB_HOSTNAME ] ; then
-			EXTRA=" --host=$DB_HOSTNAME --protocol=tcp"
-		fi
-	fi
-
-	# create database
-	mysqladmin create $DB_NAME --user="$DB_USER" --password="$DB_PASS"$EXTRA
-}
-
-install_wp
-install_test_suite
-install_db
diff --git a/bin/phpunit-test.sh b/bin/phpunit-test.sh
deleted file mode 100755
index ae53b42..0000000
--- a/bin/phpunit-test.sh
+++ /dev/null
@@ -1,29 +0,0 @@
-#!/bin/bash
-
-set -e
-
-DIRNAME=$(dirname "$0")
-
-echo "🤔 Installing WP Unit tests..."
-bash "${DIRNAME}/install-wp-tests.sh" wordpress_test root root 127.0.0.1 latest
-
-echo "📄 Copying wp-latest.json..."
-cp /tmp/wp-latest.json "${DIRNAME}/../tests/wp-latest.json"
-
-echo "🏃‍♂️ Running PHPUnit on Single Site"
-composer phpunit --ansi
-
-echo "🧹 Removing files before testing nightly WP..."
-rm -rf "$WP_TESTS_DIR" "$WP_CORE_DIR"
-rm "${DIRNAME}/../tests/wp-latest.json"
-
-echo "🤔 Installing WP Unit tests with WP nightly version..."
-bash "${DIRNAME}/install-wp-tests.sh" wordpress_test root root 127.0.0.1 nightly true
-echo "📄 Copying wp-latest.json..."
-cp /tmp/wp-latest.json "${DIRNAME}/../tests/wp-latest.json"
-echo "🏃‍♂️ Running PHPUnit on Single Site (Nightly WordPress)"
-composer phpunit --ansi
-
-bash "${DIRNAME}/install-wp-tests.sh" wordpress_test root root 127.0.0.1 latest true
-echo "🏃‍♂️ Running PHPUnit on Multisite"
-composer test:multisite --ansi
diff --git a/composer.json b/composer.json
index 2852cb7..b5c1fd9 100644
--- a/composer.json
+++ b/composer.json
@@ -8,15 +8,26 @@
   },
   "require-dev": {
     "pantheon-systems/pantheon-wp-coding-standards": "^2.0",
+    "pantheon-systems/wpunit-helpers": "^2.0",
     "phpunit/phpunit": "^9",
     "yoast/phpunit-polyfills": "^2.0"
   },
   "config": {
     "allow-plugins": {
-      "dealerdirect/phpcodesniffer-composer-installer": true
+      "dealerdirect/phpcodesniffer-composer-installer": true,
+      "pantheon-systems/wpunit-helpers": true
     }
   },
   "scripts": {
+    "chmod-scripts": [
+      "chmod +x bin/*.sh"
+    ],
+    "post-install-cmd": [
+      "@chmod-scripts"
+    ],
+    "post-update-cmd": [
+      "@chmod-scripts"
+    ],
     "lint": [
       "@phplint",
       "@phpcs"
@@ -30,7 +41,8 @@
       "@test:multisite"
     ],
     "test:multisite": "WP_MULTISITE=1 vendor/bin/phpunit --colors=always",
-    "test:install": "bin/install-local-tests.sh --no-db",
-    "test:install:withdb": "bin/install-local-tests.sh"
+    "test:install": "bin/install-local-tests.sh --skip-db=true",
+    "test:install:withdb": "bin/install-local-tests.sh",
+    "test:install:nightly": "bin/install-local-tests.sh --version=nightly --skip-db=true"
   }
 }
diff --git a/inc/fonts.php b/inc/fonts.php
new file mode 100644
index 0000000..c029f69
--- /dev/null
+++ b/inc/fonts.php
@@ -0,0 +1,60 @@
+<?php
+/**
+ * Pantheon mu-plugin customizations to the WP_Font_Library added in WordPress 6.5
+ *
+ * @package pantheon
+ */
+
+namespace Pantheon\Fonts;
+
+/**
+ * Store the value of wp_get_upload_dir() in a global variable.
+ * This is to resolve an infinite loop when wp_get_upload_dir is used inside
+ * our filter of font_dir (because upload_dir is also being filtered).
+ *
+ * @var array $wp_upload_dir The value of wp_get_upload_dir().
+ * @see https://developer.wordpress.org/reference/functions/wp_get_upload_dir/
+ */
+$_pantheon_upload_dir = wp_get_upload_dir(); // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
+
+/**
+ * Kick off our customizations to the WP_Font_Library.
+ */
+function bootstrap() {
+	/**
+	 * Modify the fonts directory.
+	 *
+	 * By default, this is set to true, so we can override the default fonts directory from wp-content/fonts to wp-content/uploads/fonts.
+	 *
+	 * Use the filter to set to false and use the default WordPress behavior (committing fonts to your repository and pushing from dev -> test -> live).
+	 *
+	 * @param bool $modify_fonts_dir Whether to modify the fonts directory.
+	 */
+	$modify_fonts_dir = apply_filters( 'pantheon_modify_fonts_dir', true );
+
+	if ( $modify_fonts_dir ) {
+		// Use the new font_dir filter added in WordPress 6.5. See https://github.com/WordPress/gutenberg/pull/57697.
+		add_filter( 'font_dir', __NAMESPACE__ . '\\pantheon_font_dir', 9 );
+	}
+}
+add_action( 'init', __NAMESPACE__ . '\\bootstrap' );
+
+/**
+ * Define a custom font directory for the WP Font Library.
+ * Default to {WP_CONTENT_DIR}/uploads/fonts.
+ *
+ * @param array $defaults The default settings for the font directory.
+ */
+function pantheon_font_dir( $defaults ) {
+	global $_pantheon_upload_dir;
+	// Set our font directory.
+	$font_dir = $_pantheon_upload_dir['basedir'] . '/fonts';
+	$font_url = $_pantheon_upload_dir['baseurl'] . '/fonts';
+
+	$defaults['path'] = $font_dir;
+	$defaults['url'] = $font_url;
+	$defaults['basedir'] = $font_dir;
+	$defaults['baseurl'] = $font_url;
+
+	return $defaults;
+}
diff --git a/pantheon.php b/pantheon.php
index 639db31..940e5a1 100644
--- a/pantheon.php
+++ b/pantheon.php
@@ -18,6 +18,10 @@
 	if ( ! defined( 'DISABLE_PANTHEON_UPDATE_NOTICES' ) || ! DISABLE_PANTHEON_UPDATE_NOTICES ) {
 		require_once 'inc/pantheon-updates.php';
 	}
+	// If the WP Font Library exists, we can add our font directory modifications. Use version_compare because the Font Library isn't actually loaded yet.
+	if ( version_compare( _pantheon_get_current_wordpress_version(), '6.5' ) ) {
+		require_once 'inc/fonts.php';
+	}   
 	if ( ! defined( 'RETURN_TO_PANTHEON_BUTTON' ) || RETURN_TO_PANTHEON_BUTTON ) {
 		require_once 'inc/pantheon-login-form-mods.php';
 	}
diff --git a/tests/phpunit/test-fonts.php b/tests/phpunit/test-fonts.php
new file mode 100644
index 0000000..d2e4b3f
--- /dev/null
+++ b/tests/phpunit/test-fonts.php
@@ -0,0 +1,188 @@
+<?php
+/**
+ * Pantheon MU Plugin Font Library Tests
+ * 
+ * @package pantheon
+ */
+
+use Pantheon\Fonts;
+
+use function Pantheon\Fonts\pantheon_modify_fonts_dir;
+
+/**
+ * Main Mu Plugin Test Case
+ */
+class Test_Fonts extends WP_UnitTestCase {
+	/**
+	 * The original pantheon upload directory.
+	 * We use this to restore the original value after we run the tests.
+	 *
+	 * @var array
+	 */
+	protected $original_pantheon_upload_dir;
+
+	public function setUp(): void {
+		parent::setUp();
+		remove_all_filters( 'font_dir' );
+		remove_all_filters( 'pantheon_modify_fonts_dir' );
+
+		// Mock the global variable before each test.
+		global $_pantheon_upload_dir;
+		$this->original_pantheon_upload_dir = $_pantheon_upload_dir; // Backup original global if needed.
+
+		// Manually set the global variable to a mocked value.
+		$_pantheon_upload_dir = [
+			'basedir' => WP_CONTENT_DIR . '/uploads',
+			'baseurl' => 'http://example.org/wp-content/uploads',
+		];      
+	}
+
+	public function tearDown(): void {
+		// Restore original global state after each test if necessary.
+		global $_pantheon_upload_dir;
+		$_pantheon_upload_dir = $this->original_pantheon_upload_dir;
+
+		parent::tearDown();     
+	}
+
+	/**
+	 * Test the font library modifications have been loaded.
+	 */
+	public function test_font_library_modifications() {
+		$this->assertTrue( function_exists( 'Pantheon\Fonts\bootstrap' ) );
+		$this->assertEquals( has_action( 'init', 'Pantheon\Fonts\bootstrap' ), 10 );
+	}
+
+	/**
+	 * Test the pantheon_font_dir function.
+	 */ 
+	public function test_pantheon_font_dir() {
+		$this->assertTrue( function_exists( 'Pantheon\Fonts\pantheon_font_dir' ) );
+
+		$this->maybe_get_font_library();
+		if ( ! function_exists( 'wp_get_font_dir' ) ) {
+			// If the function still doesn't exist after trying to get the font library from gutenberg, mark the test skipped.
+			$this->markTestSkipped( 'The wp_get_font_dir function is not available. We\'re probably not using WP 6.5+' );
+		}
+
+		// Remove the filters we apply to `font_dir` so we're getting the default data.
+		remove_all_filters( 'font_dir' );
+		$default_fonts = wp_get_font_dir();
+		$font_dir = Fonts\pantheon_font_dir( $default_fonts );
+
+		$this->assertNotEquals( $default_fonts, $font_dir );
+		$this->assertEquals( array_keys( $default_fonts ), array_keys( $font_dir ) );
+		$this->assertArrayHasKey( 'path', $font_dir );
+		$this->assertArrayHasKey( 'url', $font_dir );
+		$this->assertArrayHasKey( 'basedir', $font_dir );
+		$this->assertArrayHasKey( 'baseurl', $font_dir );
+		$this->assertStringContainsString( 'uploads/fonts', $font_dir['path'] );
+		$this->assertStringContainsString( 'uploads/fonts', $font_dir['url'] );
+		$this->assertStringContainsString( 'uploads/fonts', $font_dir['basedir'] );
+		$this->assertStringContainsString( 'uploads/fonts', $font_dir['baseurl'] );
+	}
+
+	/**
+	 * Test that our filtered font directory is filtered properly.
+	 */
+	public function test_pantheon_font_dir_filter() {
+		$this->maybe_get_font_library();
+		if ( ! function_exists( 'wp_get_font_dir' ) ) {
+			// If the function still doesn't exist after trying to get the font library from gutenberg, mark the test skipped.
+			$this->markTestSkipped( 'The wp_get_font_dir function is not available. We\'re probably not using WP 6.5+' );
+		}
+
+		add_filter( 'font_dir', '\\Pantheon\\Fonts\\pantheon_font_dir' );
+		$font_dir = wp_get_font_dir();
+		
+		$expected = [
+			'path' => WP_CONTENT_DIR . '/uploads/fonts',
+			'url' => WP_CONTENT_URL . '/uploads/fonts',
+			'subdir' => '',
+			'basedir' => WP_CONTENT_DIR . '/uploads/fonts',
+			'baseurl' => WP_CONTENT_URL . '/uploads/fonts',
+			'error' => false,
+		];
+
+		$this->assertEquals( $expected, $font_dir );
+	}
+
+	/**
+	 * Test that using the font_dir filter at priority 10 overrides our modifications.
+	 */
+	public function test_pantheon_fonts_dir_filter() {
+		$this->maybe_get_font_library();
+		if ( ! function_exists( 'wp_get_font_dir' ) ) {
+			// If the function still doesn't exist after trying to get the font library from gutenberg, mark the test skipped.
+			$this->markTestSkipped( 'The wp_get_font_dir function is not available. We\'re probably not using WP 6.5+' );
+		}
+
+		$custom_directory = [
+			'path' => WP_CONTENT_DIR . '/custom-fonts',
+			'url' => WP_CONTENT_URL . '/custom-fonts',
+			'basedir' => WP_CONTENT_DIR . '/custom-fonts',
+			'baseurl' => WP_CONTENT_URL . '/custom-fonts',
+		];
+
+		add_filter( 'font_dir', function ( $defaults ) use ( $custom_directory ) {
+			$defaults['path'] = $custom_directory['path'];
+			$defaults['url'] = $custom_directory['url'];
+			$defaults['basedir'] = $custom_directory['basedir'];
+			$defaults['baseurl'] = $custom_directory['baseurl'];
+			return $defaults;
+		} );
+
+		Fonts\bootstrap();
+		$font_dir = wp_get_font_dir();
+
+		$expected = [
+			'path' => WP_CONTENT_DIR . '/custom-fonts',
+			'url' => WP_CONTENT_URL . '/custom-fonts',
+			'subdir' => '',
+			'basedir' => WP_CONTENT_DIR . '/custom-fonts',
+			'baseurl' => WP_CONTENT_URL . '/custom-fonts',
+			'error' => false,
+		];
+
+		$this->assertEquals( $expected, $font_dir );
+	}
+
+	/**
+	 * Test that the font directory modifications can be disabled.
+	 */
+	public function test_disable_pantheon_font_dir_mods() {
+		$this->maybe_get_font_library();
+		if ( ! function_exists( 'wp_get_font_dir' ) ) {
+			// If the function still doesn't exist after trying to get the font library from gutenberg, mark the test skipped.
+			$this->markTestSkipped( 'The wp_get_font_dir function is not available. We\'re probably not using WP 6.5+' );
+		}
+
+		// Disable the font directory modifications.
+		add_filter( 'pantheon_modify_fonts_dir', '__return_false' );
+		$modify_fonts_dir = apply_filters( 'pantheon_modify_fonts_dir', true );
+		$this->assertFalse( $modify_fonts_dir );
+
+		$font_dir = wp_get_font_dir();
+
+		$expected = [
+			'path' => WP_CONTENT_DIR . '/fonts',
+			'url' => WP_CONTENT_URL . '/fonts',
+			'subdir' => '',
+			'basedir' => WP_CONTENT_DIR . '/fonts',
+			'baseurl' => WP_CONTENT_URL . '/fonts',
+			'error' => false,
+		];
+
+		$this->assertEquals( $expected, $font_dir );
+	}
+
+	/**
+	 * Get the font library from Gutenberg if it's not available.
+	 */
+	private function maybe_get_font_library() {
+		$fonts_php = WP_PLUGIN_DIR . '/gutenberg/lib/compat/wordpress-6.5/fonts/fonts.php';
+		if ( ! function_exists( 'wp_get_font_dir' ) && file_exists( $fonts_php ) ) {
+			require_once $fonts_php;
+		}
+	}
+}
diff --git a/tests/phpunit/test-pantheon-updates.php b/tests/phpunit/test-pantheon-updates.php
index 02a7f23..a703c4e 100644
--- a/tests/phpunit/test-pantheon-updates.php
+++ b/tests/phpunit/test-pantheon-updates.php
@@ -30,8 +30,9 @@ public function __construct() {
 	 * @return string|bool The latest WordPress version or false if the file doesn't exist.
 	 */
 	private static function get_latest_wp_version_from_file() {
-		$file = dirname( __DIR__ ) . '/wp-latest.json';
-
+		global $_tests_dir;
+		
+		$file = dirname( $_tests_dir ) . '/wp-latest.json';
 		if ( ! file_exists( $file ) ) {
 			return false;
 		}
@@ -65,7 +66,11 @@ public function test_pantheon_get_current_wordpress_version() {
 		// Run the function.
 		$result = _pantheon_get_current_wordpress_version();
 		$current_version = self::get_latest_wp_version_from_file();
-
+		
+		// If the current version is greater than the result, then we downloaded a nightly version for testing.
+		if ( $this->is_prerelease() ) {
+			$this->markTestSkipped( 'The current version is greater than the result. We downloaded a nightly version for testing.' );
+		}
 		// Check that the returned version is correct. This value needs to be changed when the WordPress version is updated.
 		$this->assertEquals( $current_version, $result );
 	}
@@ -101,6 +106,10 @@ public function test_pantheon_get_latest_wordpress_version() {
 	 * Test the _pantheon_upstream_update_notice function for latest core.
 	 */
 	public function test_pantheon_upstream_update_notice_core_latest() {
+		if ( $this->is_prerelease() ) {
+			$this->markTestSkipped( 'The current version is greater than the result. We will get a different message than the one this test expects.' );
+		}
+
 		set_current_screen( 'update-core' );
 	
 		// Simulate that the core is the latest version.
@@ -129,6 +138,10 @@ public function test_pantheon_upstream_update_notice_core_latest() {
 	 * Test the _pantheon_upstream_update_notice function for older core.
 	 */
 	public function test_pantheon_upstream_update_notice_core_not_latest() {
+		if ( $this->is_prerelease() ) {
+			$this->markTestSkipped( 'The current version is greater than the result. We will get a different message than the one this test expects.' );
+		}
+
 		set_current_screen( 'update-core' );
 	
 		// Simulate that the core is not the latest version.
@@ -158,14 +171,38 @@ public function test_pantheon_upstream_update_notice_core_not_latest() {
 	 */
 	private static function get_next_beta_version() {
 		$version_parts = explode( '.', self::$wp_version );
-		$version_parts[2] = (int) $version_parts[2] + 1;
+		$version_parts[1] = (int) $version_parts[1] + 1;
 		return implode( '.', $version_parts ) . '-beta';
 	}
 
+	/**
+	 * Check if we're using a beta version.
+	 */
+	private static function is_prerelease() {
+		$current_version = _pantheon_get_current_wordpress_version();
+		$installed_version = self::get_latest_wp_version_from_file();
+
+		// If the current version and the installed version are the same, then we're not using a prerelease.
+		if ( $current_version === $installed_version ) {
+			return false;
+		}
+
+		// If the version derived from WordPress is higher than the version in the wp-version.json file, then we're using a prerelease.
+		if ( version_compare( $current_version, $installed_version, '>' ) ) {
+			return true;
+		}
+
+		return false;
+	}
+
 	/**
 	 * Test the _pantheon_upstream_update_notice function for beta/pre-release version.
 	 */
 	public function test_pantheon_upstream_update_notice_core_prerelease() {
+		if ( $this->is_prerelease() ) {
+			$this->markTestSkipped( 'The current version is greater than the result. We will get a different message than the one this test expects.' );
+		}
+
 		$beta_version = self::get_next_beta_version();
 		set_current_screen( 'update-core' );