diff --git a/includes/MslsMain.php b/includes/MslsMain.php
index d3a6499d..7bff4583 100644
--- a/includes/MslsMain.php
+++ b/includes/MslsMain.php
@@ -58,11 +58,12 @@ public static function init() {
 	 *
 	 * @param mixed $message
 	 */
-	public function debugger( $message ) {
+	public function debugger( $message ): void {
 		if ( defined( 'WP_DEBUG' ) && WP_DEBUG === true ) {
 			if ( is_array( $message ) || is_object( $message ) ) {
 				$message = print_r( $message, true );
 			}
+
 			error_log( 'MSLS Debug: ' . $message );
 		}
 	}
diff --git a/phpunit.xml b/phpunit.xml
index 4a147f1e..08aacf4b 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -7,6 +7,7 @@
   </coverage>
   <php>
     <const name="MSLS_PLUGIN_PATH" value="multisite-language-switcher/MultisiteLanguageSwitcher.php"/>
+    <const name="WP_DEBUG" value="true"/>
   </php>
   <testsuite name="Internal tests">
     <directory prefix="test-" suffix=".php">./tests/</directory>
diff --git a/tests/test-mslsmain.php b/tests/test-mslsmain.php
index 4669fe54..781917ed 100644
--- a/tests/test-mslsmain.php
+++ b/tests/test-mslsmain.php
@@ -24,13 +24,13 @@ public function get_sut() {
 		return new MslsMain( $options, $collection );
 	}
 
-	function test_get_input_array() {
+	public function test_get_input_array(): void {
 		$obj = $this->get_sut();
 
 		$this->assertIsArray( $obj->get_input_array( 0 ) );
 	}
 
-	function test_is_autosave_method() {
+	public function test_is_autosave(): void {
 		Functions\when( 'wp_is_post_revision' )->justReturn( true );
 
 		$obj = $this->get_sut();
@@ -38,10 +38,34 @@ function test_is_autosave_method() {
 		$this->assertIsBool( $obj->is_autosave( 0 ) );
 	}
 
-	function test_verify_nonce_method() {
+	public function test_verify_nonce(): void {
 		$obj = $this->get_sut();
 
 		$this->assertFalse( $obj->verify_nonce() );
 	}
 
+	public function test_debugger_string(): void {
+		$capture = tmpfile();
+		$backup = ini_set('error_log', stream_get_meta_data( $capture )['uri']);
+
+		$obj = $this->get_sut();
+		$obj->debugger( 'Test' );
+
+		$this->assertStringContainsString( 'MSLS Debug: Test', stream_get_contents( $capture ) );
+
+		ini_set('error_log', $backup);
+	}
+
+	public function test_debugger_object(): void {
+		$capture = tmpfile();
+		$backup = ini_set('error_log', stream_get_meta_data( $capture )['uri']);
+
+		$obj = $this->get_sut();
+		$obj->debugger( (object) [ 'test' => 'msls' ] );
+
+		$this->assertStringContainsString( '[test] => msls', stream_get_contents( $capture ) );
+
+		ini_set('error_log', $backup);
+	}
+
 }