diff --git a/.travis.yml b/.travis.yml
index b0f0e980..46b322af 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -22,7 +22,7 @@ services:
 
 env:
   - WP_VERSION=latest WP_MULTISITE=0
-  - WP_VERSION=5.8 WP_MULTISITE=0
+  - WP_VERSION=5.9 WP_MULTISITE=0
 
 jobs:
   include:
diff --git a/common.php b/common.php
index 691649a2..b9e4a431 100644
--- a/common.php
+++ b/common.php
@@ -14751,6 +14751,17 @@ function ewwwio_debug_message( $message ) {
 	if ( ! is_string( $message ) && ! is_int( $message ) && ! is_float( $message ) ) {
 		return;
 	}
+	if ( defined( 'EIO_PHPUNIT' ) && EIO_PHPUNIT ) {
+		if (
+			! empty( $_SERVER['argv'] ) &&
+			( in_array( '--debug', $_SERVER['argv'], true ) || in_array( '--verbose', $_SERVER['argv'], true ) )
+		) {
+			$message = str_replace( '<br>', "\n", $message );
+			$message = str_replace( '<b>', '+', $message );
+			$message = str_replace( '</b>', '+', $message );
+			echo esc_html( $message ) . "\n";
+		}
+	}
 	$message = "$message";
 	if ( defined( 'WP_CLI' ) && WP_CLI ) {
 		WP_CLI::debug( $message );
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index c4274a17..87d7bc14 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -24,5 +24,11 @@ function _manually_load_plugin() {
 	define( 'EIO_PHPUNIT', true );
 }
 
+if ( ! empty( $_SERVER['HOME'] ) ) {
+	if ( is_file( $_SERVER['HOME'] . '/Documents/GitHub/PHPUnit-Polyfills/phpunitpolyfills-autoload.php' ) ) {
+		require( $_SERVER['HOME'] . '/Documents/GitHub/PHPUnit-Polyfills/phpunitpolyfills-autoload.php' );
+	}
+}
+
 // Start up the WP testing environment.
 require $_tests_dir . '/includes/bootstrap.php';
diff --git a/tests/test-agr.php b/tests/test-agr.php
index 382a4bf8..003f96bf 100644
--- a/tests/test-agr.php
+++ b/tests/test-agr.php
@@ -93,7 +93,7 @@ function tear_down() {
 		delete_option( 'ewww_image_optimizer_cloud_key' );
 		delete_site_option( 'ewww_image_optimizer_version' );
 		delete_site_option( 'ewww_image_optimizer_cloud_key' );
-		parent::tearDown();
+		parent::tear_down();
 	}
 
 	/**
diff --git a/tests/test-convert.php b/tests/test-convert.php
index 4aa1d4ba..dbd8cedf 100644
--- a/tests/test-convert.php
+++ b/tests/test-convert.php
@@ -341,7 +341,7 @@ function tear_down() {
 		delete_option( 'ewww_image_optimizer_cloud_key' );
 		delete_site_option( 'ewww_image_optimizer_version' );
 		delete_site_option( 'ewww_image_optimizer_cloud_key' );
-		parent::tearDown();
+		parent::tear_down();
 	}
 
 	/**
diff --git a/tests/test-optimize.php b/tests/test-optimize.php
index c1a86493..baa04f8b 100644
--- a/tests/test-optimize.php
+++ b/tests/test-optimize.php
@@ -94,7 +94,7 @@ public static function set_up_before_class() {
 	 * Initializes the plugin and installs the ewwwio_images table.
 	 */
 	function set_up() {
-		parent::setUp();
+		parent::set_up();
 		remove_filter( 'query', array( $this, '_create_temporary_tables' ) );
 		ewww_image_optimizer_install_table();
 		add_filter( 'query', array( $this, '_create_temporary_tables' ) );
@@ -380,7 +380,7 @@ function test_optimize_png_40_optipng() {
 		update_site_option( 'ewww_image_optimizer_optipng_level', 2 );
 		update_site_option( 'ewww_image_optimizer_metadata_remove', true );
 		$results = $this->optimize_png();
-		$this->assertEquals( 38603, filesize( $results[0] ) );
+		$this->assertLessThanOrEqual( 39000, filesize( $results[0] ) );
 		unlink( $results[0] );
 	}
 
@@ -563,7 +563,7 @@ function tear_down() {
 		delete_option( 'ewww_image_optimizer_cloud_key' );
 		delete_site_option( 'ewww_image_optimizer_version' );
 		delete_site_option( 'ewww_image_optimizer_cloud_key' );
-		parent::tearDown();
+		parent::tear_down();
 	}
 
 	/**
diff --git a/tests/test-resize.php b/tests/test-resize.php
index 8d025182..5e2b3ca3 100644
--- a/tests/test-resize.php
+++ b/tests/test-resize.php
@@ -48,7 +48,7 @@ public static function set_up_before_class() {
 	 * Initializes the plugin and installs the ewwwio_images table.
 	 */
 	function set_up() {
-		parent::setUp();
+		parent::set_up();
 		remove_filter( 'query', array( $this, '_create_temporary_tables' ) );
 		ewww_image_optimizer_install_table();
 		add_filter( 'query', array( $this, '_create_temporary_tables' ) );
@@ -132,6 +132,21 @@ function test_crop_jpg_cloud() {
 		$this->assertEquals( 1024, $height );
 	}
 
+	/**
+	 * Cleans up ewwwio_images table.
+	 */
+	function tear_down() {
+		global $wpdb;
+		remove_filter( 'query', array( $this, '_drop_temporary_tables' ) );
+		$wpdb->query( "DROP TABLE IF EXISTS $wpdb->ewwwio_images" );
+		add_filter( 'query', array( $this, '_drop_temporary_tables' ) );
+		delete_option( 'ewww_image_optimizer_version' );
+		delete_option( 'ewww_image_optimizer_cloud_key' );
+		delete_site_option( 'ewww_image_optimizer_version' );
+		delete_site_option( 'ewww_image_optimizer_cloud_key' );
+		parent::tear_down();
+	}
+
 	/**
 	 * Cleans up the temp images.
 	 */
diff --git a/tests/test-tables.php b/tests/test-tables.php
index 6462e3e4..88faf6af 100644
--- a/tests/test-tables.php
+++ b/tests/test-tables.php
@@ -40,7 +40,7 @@ public static function set_up_before_class() {
 	 * Initializes the plugin and installs the ewwwio_images table.
 	 */
 	function set_up() {
-		parent::setUp();
+		parent::set_up();
 		remove_filter( 'query', array( $this, '_create_temporary_tables' ) );
 		ewww_image_optimizer_install_table();
 		add_filter( 'query', array( $this, '_create_temporary_tables' ) );
@@ -117,7 +117,7 @@ function tear_down() {
 		add_filter( 'query', array( $this, '_drop_temporary_tables' ) );
 		delete_option( 'ewww_image_optimizer_version' );
 		delete_site_option( 'ewww_image_optimizer_version' );
-		parent::tearDown();
+		parent::tear_down();
 	}
 
 	/**