test if bundle for supported locales exist and are not empty

src/test/java/org/cryptomator/launcher/SupportedLanguagesTest.java

@@ -0,0 +1,31 @@
+package org.cryptomator.launcher;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import java.util.Locale;
+import java.util.ResourceBundle;
+import java.util.stream.Stream;
+
+public class SupportedLanguagesTest {
+
+	@DisplayName("test if resource bundle is localized")
+	@ParameterizedTest(name = "{0}")
+	@MethodSource("languageTags")
+	public void testResourceBundleExists(String tag) {
+		var locale = Locale.forLanguageTag(tag);
+		Assertions.assertNotEquals("und", locale.toLanguageTag(), "Undefined language tag");
+
+		var bundle = Assertions.assertDoesNotThrow(() -> ResourceBundle.getBundle("/i18n/strings", locale));
+
+		Assertions.assertEquals(locale, bundle.getLocale());
+		Assertions.assertFalse(bundle.keySet().isEmpty());
+	}
+
+	public static Stream<String> languageTags() {
+		return SupportedLanguages.LANGUAGAE_TAGS.stream() //
+				.filter(tag -> !"en".equals(tag)); // english uses the default bundle
+	}
+}