### Question:
MapperUtils { public static NamespaceId toNamespaceId(String hex) { return hex == null ? null : NamespaceId.createFromId(fromHexToBigInteger(hex)); } private  MapperUtils(); static NamespaceId toNamespaceId(String hex); static MosaicId toMosaicId(String hex); static UnresolvedMosaicId toUnresolvedMosaicId(String hex); static UnresolvedAddress toUnresolvedAddress(String hex); static Address toAddressFromRawAddress(String rawAddress); static BigInteger fromHexToBigInteger(String hex); static String fromBigIntegerToHex(BigInteger value); static Address toAddress(String encodedAddress); static String getIdAsHex(UnresolvedMosaicId id);  }### Answer:
@Test void shouldMapToNamespaceId() { Assertions.assertNull(MapperUtils.toNamespaceId(null)); Assertions.assertEquals( BigInteger.valueOf(1194684), MapperUtils.toNamespaceId("123ABC").getId()); }