Add Locale conversion format configuration property

junit-jupiter-engine/junit-jupiter-engine.gradle.kts

@@ -13,6 +13,7 @@ dependencies {
 	api(platform(projects.junitBom))
 	api(projects.junitPlatformEngine)
 	api(projects.junitJupiterApi)
+	api(projects.junitJupiterParams)
 
 	compileOnlyApi(libs.apiguardian)
 

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/config/CachingJupiterConfiguration.java

@@ -29,6 +29,7 @@
 import org.junit.jupiter.api.io.CleanupMode;
 import org.junit.jupiter.api.io.TempDirFactory;
 import org.junit.jupiter.api.parallel.ExecutionMode;
+import org.junit.jupiter.params.converter.LocaleConversionFormat;
 
 /**
  * Caching implementation of the {@link JupiterConfiguration} API.
@@ -125,4 +126,10 @@ public Supplier<TempDirFactory> getDefaultTempDirFactorySupplier() {
 			key -> delegate.getDefaultTempDirFactorySupplier());
 	}
 
+	@Override
+	public LocaleConversionFormat getDefaultLocaleConversionFormat() {
+		return (LocaleConversionFormat) cache.computeIfAbsent(DEFAULT_LOCALE_CONVERSION_FORMAT_PROPERTY_NAME,
+			key -> delegate.getDefaultLocaleConversionFormat());
+	}
+
 }

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/config/DefaultJupiterConfiguration.java

@@ -14,6 +14,7 @@
 import static org.junit.jupiter.api.io.CleanupMode.ALWAYS;
 import static org.junit.jupiter.api.io.TempDir.DEFAULT_CLEANUP_MODE_PROPERTY_NAME;
 import static org.junit.jupiter.api.io.TempDir.DEFAULT_FACTORY_PROPERTY_NAME;
+import static org.junit.jupiter.params.converter.LocaleConversionFormat.ISO_639;
 
 import java.util.Optional;
 import java.util.function.Function;
@@ -29,6 +30,7 @@
 import org.junit.jupiter.api.io.CleanupMode;
 import org.junit.jupiter.api.io.TempDirFactory;
 import org.junit.jupiter.api.parallel.ExecutionMode;
+import org.junit.jupiter.params.converter.LocaleConversionFormat;
 import org.junit.platform.commons.util.ClassNamePatternFilterUtils;
 import org.junit.platform.commons.util.Preconditions;
 import org.junit.platform.engine.ConfigurationParameters;
@@ -62,6 +64,9 @@ public class DefaultJupiterConfiguration implements JupiterConfiguration {
 	private static final InstantiatingConfigurationParameterConverter<TempDirFactory> tempDirFactoryConverter = //
 		new InstantiatingConfigurationParameterConverter<>(TempDirFactory.class, "temp dir factory");
 
+	private static final EnumConfigurationParameterConverter<LocaleConversionFormat> localeConversionFormatConverter = //
+		new EnumConfigurationParameterConverter<>(LocaleConversionFormat.class, "locale conversion format");
+
 	private final ConfigurationParameters configurationParameters;
 
 	public DefaultJupiterConfiguration(ConfigurationParameters configurationParameters) {
@@ -141,4 +146,10 @@ public Supplier<TempDirFactory> getDefaultTempDirFactorySupplier() {
 		return () -> supplier.get().orElse(TempDirFactory.Standard.INSTANCE);
 	}
 
+	@Override
+	public LocaleConversionFormat getDefaultLocaleConversionFormat() {
+		return localeConversionFormatConverter.get(configurationParameters,
+			DEFAULT_LOCALE_CONVERSION_FORMAT_PROPERTY_NAME, ISO_639);
+	}
+
 }

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/config/JupiterConfiguration.java

@@ -27,6 +27,7 @@
 import org.junit.jupiter.api.io.TempDirFactory;
 import org.junit.jupiter.api.parallel.Execution;
 import org.junit.jupiter.api.parallel.ExecutionMode;
+import org.junit.jupiter.params.converter.LocaleConversionFormat;
 
 /**
  * @since 5.4
@@ -43,6 +44,7 @@ public interface JupiterConfiguration {
 	String DEFAULT_DISPLAY_NAME_GENERATOR_PROPERTY_NAME = DisplayNameGenerator.DEFAULT_GENERATOR_PROPERTY_NAME;
 	String DEFAULT_TEST_METHOD_ORDER_PROPERTY_NAME = MethodOrderer.DEFAULT_ORDER_PROPERTY_NAME;
 	String DEFAULT_TEST_CLASS_ORDER_PROPERTY_NAME = ClassOrderer.DEFAULT_ORDER_PROPERTY_NAME;
+	String DEFAULT_LOCALE_CONVERSION_FORMAT_PROPERTY_NAME = "junit.jupiter.params.arguments.conversion.locale.format";
 
 	Optional<String> getRawConfigurationParameter(String key);
 
@@ -70,4 +72,6 @@ public interface JupiterConfiguration {
 
 	Supplier<TempDirFactory> getDefaultTempDirFactorySupplier();
 
+	LocaleConversionFormat getDefaultLocaleConversionFormat();
+
 }

junit-jupiter-engine/src/module/org.junit.jupiter.engine/module-info.java

@@ -20,6 +20,7 @@
 module org.junit.jupiter.engine {
 	requires static org.apiguardian.api;
 	requires org.junit.jupiter.api;
+	requires org.junit.jupiter.params.converter;
 	requires org.junit.platform.commons;
 	requires org.junit.platform.engine;
 	requires org.opentest4j;

junit-jupiter-engine/src/test/java/org/junit/jupiter/engine/config/CachingJupiterConfigurationTests.java

@@ -12,6 +12,7 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.io.CleanupMode.NEVER;
+import static org.junit.jupiter.params.converter.LocaleConversionFormat.ISO_639;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.only;
 import static org.mockito.Mockito.times;
@@ -95,7 +96,7 @@ void cachesDefaultDisplayNameGenerator() {
 		CustomDisplayNameGenerator customDisplayNameGenerator = new CustomDisplayNameGenerator();
 		when(delegate.getDefaultDisplayNameGenerator()).thenReturn(customDisplayNameGenerator);
 
-		// call `cache.getDefaultDisplayNameGenerator()` twice to verify the delegate method is called only once.
+		// call twice to verify the delegate method is called only once.
 		assertThat(cache.getDefaultDisplayNameGenerator()).isSameAs(customDisplayNameGenerator);
 		assertThat(cache.getDefaultDisplayNameGenerator()).isSameAs(customDisplayNameGenerator);
 
@@ -107,7 +108,7 @@ void cachesDefaultTestMethodOrderer() {
 		final Optional<MethodOrderer> methodOrderer = Optional.of(new MethodOrderer.MethodName());
 		when(delegate.getDefaultTestMethodOrderer()).thenReturn(methodOrderer);
 
-		// call `cache.getDefaultTestMethodOrderer()` twice to verify the delegate method is called only once.
+		// call twice to verify the delegate method is called only once.
 		assertThat(cache.getDefaultTestMethodOrderer()).isSameAs(methodOrderer);
 		assertThat(cache.getDefaultTestMethodOrderer()).isSameAs(methodOrderer);
 
@@ -118,7 +119,7 @@ void cachesDefaultTestMethodOrderer() {
 	void cachesDefaultTempDirCleanupMode() {
 		when(delegate.getDefaultTempDirCleanupMode()).thenReturn(NEVER);
 
-		// call `cache.getDefaultTempStrategyDirCleanupMode()` twice to verify the delegate method is called only once.
+		// call twice to verify the delegate method is called only once.
 		assertThat(cache.getDefaultTempDirCleanupMode()).isSameAs(NEVER);
 		assertThat(cache.getDefaultTempDirCleanupMode()).isSameAs(NEVER);
 
@@ -130,13 +131,24 @@ void cachesDefaultTempDirFactorySupplier() {
 		Supplier<TempDirFactory> supplier = mock();
 		when(delegate.getDefaultTempDirFactorySupplier()).thenReturn(supplier);
 
-		// call `cache.getDefaultTempDirFactorySupplier()` twice to verify the delegate method is called only once.
+		// call twice to verify the delegate method is called only once.
 		assertThat(cache.getDefaultTempDirFactorySupplier()).isSameAs(supplier);
 		assertThat(cache.getDefaultTempDirFactorySupplier()).isSameAs(supplier);
 
 		verify(delegate, only()).getDefaultTempDirFactorySupplier();
 	}
 
+	@Test
+	void cachesDefaultLocaleConversionFormat() {
+		when(delegate.getDefaultLocaleConversionFormat()).thenReturn(ISO_639);
+
+		// call twice to verify the delegate method is called only once.
+		assertThat(cache.getDefaultLocaleConversionFormat()).isSameAs(ISO_639);
+		assertThat(cache.getDefaultLocaleConversionFormat()).isSameAs(ISO_639);
+
+		verify(delegate, only()).getDefaultLocaleConversionFormat();
+	}
+
 	@Test
 	void doesNotCacheRawParameters() {
 		when(delegate.getRawConfigurationParameter("foo")).thenReturn(Optional.of("bar")).thenReturn(

junit-jupiter-engine/src/test/java/org/junit/jupiter/engine/config/DefaultJupiterConfigurationTests.java

@@ -17,6 +17,7 @@
 import static org.junit.jupiter.api.TestInstance.Lifecycle.PER_METHOD;
 import static org.junit.jupiter.api.io.CleanupMode.ALWAYS;
 import static org.junit.jupiter.engine.Constants.DEFAULT_TEST_INSTANCE_LIFECYCLE_PROPERTY_NAME;
+import static org.junit.jupiter.params.converter.LocaleConversionFormat.ISO_639;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
@@ -34,6 +35,7 @@
 import org.junit.jupiter.api.io.TempDirFactory;
 import org.junit.jupiter.engine.Constants;
 import org.junit.jupiter.engine.descriptor.CustomDisplayNameGenerator;
+import org.junit.jupiter.params.converter.LocaleConversionFormat;
 import org.junit.platform.commons.PreconditionViolationException;
 import org.junit.platform.engine.ConfigurationParameters;
 
@@ -145,6 +147,13 @@ void shouldGetStandardAsDefaultTempDirFactorySupplierWithoutConfigParamSet() {
 		assertThat(supplier.get()).isSameAs(TempDirFactory.Standard.INSTANCE);
 	}
 
+	@Test
+	void shouldGetDefaultLocaleConversionFormatWithNoConfigParamSet() {
+		JupiterConfiguration configuration = new DefaultJupiterConfiguration(mock());
+		LocaleConversionFormat localeConversionFormat = configuration.getDefaultLocaleConversionFormat();
+		assertThat(localeConversionFormat).isEqualTo(ISO_639);
+	}
+
 	private void assertDefaultConfigParam(String configValue, Lifecycle expected) {
 		ConfigurationParameters configParams = mock();
 		when(configParams.get(KEY)).thenReturn(Optional.ofNullable(configValue));

junit-jupiter-params/src/main/java/org/junit/jupiter/params/converter/LocaleConversionFormat.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2015-2023 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * https://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junit.jupiter.params.converter;
+
+import static org.apiguardian.api.API.Status.INTERNAL;
+
+import org.apiguardian.api.API;
+
+/**
+ * Enumeration of {@link java.util.Locale} conversion formats.
+ *
+ * @since 5.11
+ */
+@API(status = INTERNAL, since = "5.11")
+public enum LocaleConversionFormat {
+
+	/**
+	 * The ISO 639 alpha-2 or alpha-3 language code format.
+	 *
+	 * @see java.util.Locale#Locale(String)
+	 */
+	ISO_639,
+
+	/**
+	 * The IETF BCP 47 language tag format.
+	 *
+	 * @see java.util.Locale#forLanguageTag(String)
+	 */
+	BCP_47
+
+}

junit-jupiter-params/src/main/java/org/junit/jupiter/params/converter/StringToLocaleConverter.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2015-2023 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * https://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junit.jupiter.params.converter;
+
+import java.util.Locale;
+import java.util.function.Function;
+
+import org.junit.platform.commons.util.Preconditions;
+
+class StringToLocaleConverter implements StringToObjectConverter {
+
+	private final Function<String, Locale> converter;
+
+	StringToLocaleConverter(LocaleConversionFormat format) {
+		Preconditions.notNull(format, "format must not be null");
+		this.converter = format == LocaleConversionFormat.ISO_639 ? Locale::new : Locale::forLanguageTag;
+	}
+
+	@Override
+	public boolean canConvert(Class<?> targetType) {
+		return targetType == Locale.class;
+	}
+
+	@Override
+	public Object convert(String source, Class<?> targetType) {
+		return converter.apply(source);
+	}
+
+}