What is the higest dosage you have ran test before? If you are still growing off that dosage, there is no need to bump it up ... You said you are still growing, so i cant see how you wont grow off 500 mg of test a week.This is just my personal opinion.
If you do choose to bump it up anyways , i would go in jumps of 250mg..So if your highest dosage before was 500mg then jump to 750, not 1000.
Way i like to see test ran is to run at same dosage until you stop growing or responding then bumps of 250,up and so on .
Not everyone does it this way and its not a must but its what i think is the safest.