code: package io.ray.runtime;
  
  import io.ray.api.id.UniqueId;
  import java.nio.ByteBuffer;
  import java.util.Arrays;
  import javax.xml.bind.DatatypeConverter;
  import org.testng.Assert;
  import org.testng.annotations.Test;
  
  public class UniqueIdTest {
  
    @Test
    public void testConstructUniqueId() {
      // Test `fromHexString()`
      UniqueId id1 =
          UniqueId.fromHexString("00000000123456789ABCDEF123456789ABCDEF0123456789ABCDEF00");
      Assert.assertEquals("00000000123456789abcdef123456789abcdef0123456789abcdef00", id1.toString());
      Assert.assertFalse(id1.isNil());
  
      try {
        UniqueId id2 =
            UniqueId.fromHexString("000000123456789ABCDEF123456789ABCDEF0123456789ABCDEF00");
        // This shouldn't be happened.
        Assert.assertTrue(false);
      } catch (IllegalArgumentException e) {
        Assert.assertTrue(true);
      }
  
      try {
        UniqueId id3 = UniqueId.fromHexString("GGGGGGGGGGGGG");
        // This shouldn't be happened.
        Assert.assertTrue(false);
      } catch (IllegalArgumentException e) {
        Assert.assertTrue(true);
      }
  
      // Test `fromByteBuffer()`
      byte[] bytes =
          DatatypeConverter.parseHexBinary(
              "0123456789ABCDEF0123456789ABCDEF012345670123456789ABCDEF");
      ByteBuffer byteBuffer = ByteBuffer.wrap(bytes, 0, 28);
      UniqueId id4 = UniqueId.fromByteBuffer(byteBuffer);
      Assert.assertTrue(Arrays.equals(bytes, id4.getBytes()));
      Assert.assertEquals("0123456789abcdef0123456789abcdef012345670123456789abcdef", id4.toString());
  
      // Test `genNil()`
      UniqueId id6 = UniqueId.NIL;
      Assert.assertEquals(
          "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF".toLowerCase(), id6.toString());
      Assert.assertTrue(id6.isNil());
    }
  }
  