Add minor unit tests for HexUtil
Add minor unit tests for HexUtil

uudashr/jsmpp,pmoerenhout/jsmpp-1,chscorpio/jsmpp,pmoerenhout/jsmpp-1,openam-org-ru/org.jsmpp,uudashr/jsmpp,jojoaddison/jsmpp,jojoaddison/jsmpp,opentelecoms-org/jsmpp,kamslooce/jsmpp,amdtelecom/jsmpp,kamslooce/jsmpp,opentelecoms-org/jsmpp,chscorpio/jsmpp,amdtelecom/jsmpp,openam-org-ru/org.jsmpp