test/jdk/java/util/Locale/RequiredAvailableLocalesTest.java

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/**
 * @test
 * @bug 8276186 8174269
 * @summary Checks whether getAvailableLocales() returns at least Locale.ROOT and
 *      Locale.US instances.
 * @run testng RequiredAvailableLocalesTest
 */

import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.text.*;
import java.time.format.DecimalStyle;
import java.util.*;

import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;
import static org.testng.Assert.assertTrue;

@Test
public class RequiredAvailableLocalesTest {

    private static final Set<Locale> REQUIRED_LOCALES = Set.of(Locale.ROOT, Locale.US);
    private static final MethodType ARRAY_RETURN_TYPE = MethodType.methodType(Locale.class.arrayType());
    private static final MethodType SET_RETURN_TYPE = MethodType.methodType(Set.class);

    @DataProvider
    public Object[][] availableLocalesClasses() {
        return new Object[][] {
            {BreakIterator.class, ARRAY_RETURN_TYPE},
            {Calendar.class, ARRAY_RETURN_TYPE},
            {Collator.class, ARRAY_RETURN_TYPE},
            {DateFormat.class, ARRAY_RETURN_TYPE},
            {DateFormatSymbols.class, ARRAY_RETURN_TYPE},
            {DecimalFormatSymbols.class, ARRAY_RETURN_TYPE},
            {DecimalStyle.class, SET_RETURN_TYPE},
            {Locale.class, ARRAY_RETURN_TYPE},
            {NumberFormat.class, ARRAY_RETURN_TYPE},
        };
    }

    @Test (dataProvider = "availableLocalesClasses")
    public void checkRequiredLocales(Class<?> c, MethodType mt) throws Throwable {
        var ret = MethodHandles.lookup().findStatic(c, "getAvailableLocales", mt).invoke();

        if (ret instanceof Locale[] a) {
            assertTrue(Arrays.asList(a).containsAll(REQUIRED_LOCALES));
        } else if (ret instanceof Set<?> s) {
            assertTrue(s.containsAll(REQUIRED_LOCALES));
        } else {
            throw new RuntimeException("return type mismatch");
        }
    }
}