ZoneUtilTest 完善

hutool-core/src/test/java/cn/hutool/core/date/ZoneUtilTest.java

@@ -0,0 +1,16 @@
+package cn.hutool.core.date;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.time.ZoneId;
+import java.util.TimeZone;
+
+public class ZoneUtilTest {
+
+	@Test
+	public void test() {
+		Assert.assertEquals(ZoneId.systemDefault(), ZoneUtil.toZoneId(null));
+		Assert.assertEquals(TimeZone.getDefault(), ZoneUtil.toTimeZone(null));
+	}
+}