diff --git a/tests/TestConf.php b/tests/TestConf.php
index 4e839a5..da2dbfa 100644
--- a/tests/TestConf.php
+++ b/tests/TestConf.php
@@ -89,7 +89,7 @@ class TestConf extends \PHPUnit\Framework\TestCase {
 	/**
      * @depends testImportFile
      */
-	function testImportFileNotPHP() {
+	function testImportFileNotPhp() {
 		$this->assertException("fileCorrupt", "Conf");
 		// this should not print the output of the non-PHP file
 		$conf = new Conf(self::$path."confNotPHP");
diff --git a/tests/TestLangErrors.php b/tests/TestLangErrors.php
new file mode 100644
index 0000000..99971f3
--- /dev/null
+++ b/tests/TestLangErrors.php
@@ -0,0 +1,50 @@
+<?php
+declare(strict_types=1);
+namespace JKingWeb\NewsSync;
+use \org\bovigo\vfs\vfsStream;
+
+
+class TestLangErrors extends \PHPUnit\Framework\TestCase {
+	use TestingHelpers, LanguageTestingHelpers;
+
+	static $vfs;
+	static $path;
+	static $files;
+	static $defaultPath;
+
+	function setUp() {
+		Lang::set("", true);
+	}
+
+	function testLoadFileEmpty() {
+		$this->assertException("fileCorrupt", "Lang");
+		Lang::set("fr_ca", true);
+	}
+
+	function testLoadFileNotAnArray() {
+		$this->assertException("fileCorrupt", "Lang");
+		Lang::set("it", true);
+	}
+
+	function testLoadFileNotPhp() {
+		$this->assertException("fileCorrupt", "Lang");
+		Lang::set("ko", true);
+	}
+
+	function testLoadFileCorrupt() {
+		$this->assertException("fileCorrupt", "Lang");
+		Lang::set("zh", true);
+	}
+
+	function testLoadFileUnreadable() {
+		$this->assertException("fileUnreadable", "Lang");
+		Lang::set("ru", true);
+	}
+
+	function testLoadDefaultMissing() {
+		// this should be the last test of the series
+		unlink(self::$path.Lang::DEFAULT.".php");
+		$this->assertException("defaultFileMissing", "Lang");
+		Lang::set("fr", true);
+	}
+}
\ No newline at end of file
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index c4c2368..3df862e 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -31,6 +31,7 @@ trait LanguageTestingHelpers {
 			'fr.php'    => '<?php return ["Test.presentText" => "à l\'école des sorciers"];',
 			'ja.php'    => '<?php return ["Test.absentText"  => "賢者の石"];',
 			'de.php'    => '<?php return ["Test.presentText" => "und der Stein der Weisen"];',
+			'vi.php'    => '<?php return [];',
 			// corrupt files
 			'it.php'    => '<?php return 0;',
 			'zh.php'    => '<?php return 0',
@@ -40,12 +41,12 @@ trait LanguageTestingHelpers {
 			'ru.php'    => '',
 		];
 		self::$vfs = vfsStream::setup("langtest", 0777, self::$files);
-		self::$path = self::$vfs->url();
+		self::$path = self::$vfs->url()."/";
 		// set up a file without read access
-		chmod(self::$path."/ru.php", 0000);
+		chmod(self::$path."ru.php", 0000);
 		// make the Lang class use the vfs files
 		self::$defaultPath = Lang::$path;
-		Lang::$path = self::$path."/";
+		Lang::$path = self::$path;
 	}
 
 	static function tearDownAfterClass() {
diff --git a/tests/phpunit.xml b/tests/phpunit.xml
index 8b1dbd8..3278285 100644
--- a/tests/phpunit.xml
+++ b/tests/phpunit.xml
@@ -7,12 +7,14 @@
 	convertWarningsToExceptions="true"
 	beStrictAboutTestsThatDoNotTestAnything="true"
 	beStrictAboutOutputDuringTests="true"
-	beStrictAboutTestSize="true">
+	beStrictAboutTestSize="true"
+	stopOnError="true">
 
 <testsuite name="Localization and exceptions">
 	<file>TestLang.php</file>
 	<file>TestLangComplex.php</file>
 	<file>TestException.php</file>
+	<file>TestLangErrors.php</file>
 </testsuite>
 
 <testsuite name="Configuration loading and saving">
diff --git a/tests/testLangComplex.php b/tests/testLangComplex.php
index d02ecdb..8340d4d 100644
--- a/tests/testLangComplex.php
+++ b/tests/testLangComplex.php
@@ -47,7 +47,7 @@ class TestLangComplex extends \PHPUnit\Framework\TestCase {
 	/**
      * @depends testMessage
      */
-	function testMessageNumMSingle() {
+	function testMessageNumSingle() {
 		Lang::set("en_ca", true);
 		$this->assertEquals('Default language file "en" missing', Lang::msg('Exception.JKingWeb/NewsSync/Lang/Exception.defaultFileMissing', Lang::DEFAULT));
 	}
@@ -66,4 +66,24 @@ class TestLangComplex extends \PHPUnit\Framework\TestCase {
 	function testMessageNamed() {
 		$this->assertEquals('Message string "Test.absentText" missing from all loaded language files (en)', Lang::msg('Exception.JKingWeb/NewsSync/Lang/Exception.stringMissing', ['msgID' => 'Test.absentText', 'fileList' => 'en']));
 	}
+
+	/**
+     * @depends testMessage
+     */
+	function testReloadDefaults() {
+		Lang::set("de", true);
+		Lang::set("en", true);
+		$this->assertEquals('and the Philosopher\'s Stone', Lang::msg('Test.presentText'));
+	}
+
+	/**
+     * @depends testMessage
+     */
+	function testReloadGeneralTagAfterSubtag() {
+		Lang::set("en", true);
+		Lang::set("en_us", true);
+		$this->assertEquals('and the Sorcerer\'s Stone', Lang::msg('Test.presentText'));
+		Lang::set("en", true);
+		$this->assertEquals('and the Philosopher\'s Stone', Lang::msg('Test.presentText'));
+	}
 }
\ No newline at end of file
diff --git a/vendor/JKingWeb/NewsSync/Lang.php b/vendor/JKingWeb/NewsSync/Lang.php
index 9ae9e68..d557866 100644
--- a/vendor/JKingWeb/NewsSync/Lang.php
+++ b/vendor/JKingWeb/NewsSync/Lang.php
@@ -94,6 +94,7 @@ class Lang {
 	
 	static protected function listFiles(): array {
 		$out = glob(self::$path."*.php");
+		// built-in glob doesn't work with vfsStream (and this other glob doesn't seem to work with Windows paths), so we try both
 		if(empty($out)) $out = Glob::glob(self::$path."*.php");
 		$out = array_map(function($file) {
 			$file = str_replace(DIRECTORY_SEPARATOR, "/", $file);