RFC3339 parsing by java.time (only parsing is possible)

Rfc3339Test.java

package rfc3339;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.function.Executable;

import java.time.ZoneOffset;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.ResolverStyle;

public class Rfc3339Test {
    public static final DateTimeFormatter rfc3339Formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss[.SSS]XXX")
            .withResolverStyle(ResolverStyle.LENIENT);

    public static ZonedDateTime parseRfc3339(String rfcDateTime) {
        return ZonedDateTime.parse(rfcDateTime, rfc3339Formatter);
    }

    @Test void testHourWithTimezone() {
        int hour = parseRfc3339("2019-07-19T10:14:39.812+01:00").withZoneSameInstant(ZoneOffset.UTC).getHour();
        Assertions.assertEquals(9, hour);
    }

    @Test void testUnknownLocalOffset() {
        int hour = parseRfc3339("2019-07-19T10:14:39.812-00:00").withZoneSameInstant(ZoneOffset.UTC).getHour();
        Assertions.assertEquals(10, hour);

        System.out.println(parseRfc3339("1990-12-31T23:59:60Z"));
        System.out.println(parseRfc3339("1990-12-31T15:59:60-08:00"));
    }

    /**
     * Examples are taken from <a href="https://www.ietf.org/rfc/rfc3339.txt"> RFC 3339 standard </a>
     */
    @Test void testParsingDifferentDateTimes() {
        Assertions.assertDoesNotThrow(exParseRfc3339("1985-04-12T23:20:50.52Z"));
        Assertions.assertDoesNotThrow(exParseRfc3339("1996-12-19T16:39:57-08:00"));
        Assertions.assertDoesNotThrow(exParseRfc3339("1990-12-31T23:59:60Z"));
        Assertions.assertDoesNotThrow(exParseRfc3339("1990-12-31T15:59:60-08:00"));
        Assertions.assertDoesNotThrow(exParseRfc3339("1937-01-01T12:00:27.87+00:20"));
    }

    private static Executable exParseRfc3339(String toParse) {
        return () -> parseRfc3339(toParse);
    }
}

According https://tools.ietf.org/html/rfc3339

https://stackoverflow.com/a/55310635/1306553
https://stackoverflow.com/a/49634501/1306553