WoWInterface - Accurately Checcking Debuffs?

Alright, im wondering how to accurately check debuffs then stop my pet if it has a certain debuff.

First off, i know you use UnitDebuff, but where in the code would you put say:

Interface\\Icons\\Spell_Shadow_Possession?

This is what i got so far:

Code:

--Finding the spell

local findFear = "Spell_Shadow_Possession"



function Warlock_OnLoad()

        if( DEFAULT_CHAT_FRAME ) then

                DEFAULT_CHAT_FRAME:AddMessage("Smart Target");

        end

end



function isUnitDebuffUp(sUnitname, sDebuffname) 

  local iIterator = 1

  while (UnitDebuff(sUnitname, iIterator)) do

    if (string.find(UnitDebuff(sUnitname, iIterator), sDebuffname)) then

      return true

    end

    iIterator = iIterator + 1

  end

  return false

end



function isTargetDebuffUp(sDebuffname)

  if not sDebuffname then dbg("isTargetDebuffUp:sBuffname empty")return false end;

  return isUnitDebuffUp("target", sDebuffname) 

end;



function isFeared()

        if UnitIsDeadOrGhost("target") then return false end;

        if UnitIsFriend("player", "target") then return false end;

        return isTargetDebuffUp(findFear)

end;



function petWait()

        if(isFeared() == true) then PetWait();

        end

end

At first it works, but i have to press my pets atk key and fear at nearly the same time. Then it pretty much doesnt do it =/. Anyone know what may be causing this?