Not-Now.Soon yes true, however even worse if done other than for finding out who should pay it could break dads hearts and end real happy relationships, that may be the reason it doesn't already exist.
However,freedom to not have your DNA stored [not sure why you think like that] surely can not over rule the rights of *not the dad* who has paid for maybe decades,and maybe under great durese for children that are not his?
Consider The man who has moved on to a happy marriage with kids that are his, but has lead a lesser life because he was forced to pay for someone else's kids?

To Belly. I don't really care about our DNA being stored by givernment or anyone else. I only mentioned it because it was already brought up and can be used as an example of unintended consquences. I could be wrong here, but I would assume the number of medical tests getting wrong at birth, would be a very small number. Probabley compairable to the number of people who are accused of being the father and pay alimony, but aren't.

I wouldn't be opposed to needing a parental test before needing the father to pay alimony. But I don't think a parental test at birth is going to solve the problem as much as replacing the problem with another equally bad problem. If nothing else the test would need to be taken more then once to confirm the results, but, that's just another expense that likely isn't a concern to most people expecting a baby.

Either way though the better option I already agreed with. We need a change in culture. And encourage to not have sex as casually or as quickly as we do in relationships. For guys to keep it in their pants instead of finding out all of the issues that could come up if they don't. (This issue being one of those issues).

Not-Now.Soon I am biased on DNA last night watched my footy team win a true historic come back, too wide awake to sleep TV surfed between two true life murder docos, DNA helped solve them re-enforcing my long time view we have nothing to fear, yes, no defence, testing will bring great pain,but can it ever be fair not to test? to let not the dad/his true kids/his wife live a lessor life because he pays for someone else,if the kid next door steals a car, runs over a child, do we consider the crime? or how many others may be hurt?

This is a difficult one. If you looked after a non biological child and formed a relationship with that child and broke up with the child's parent you could request child custody under the current family law system, which is a good protection for people in that situation. See -

https://www.cudmorelegal.com.au/family-law-services/child-custody-lawyers-brisbane

The reason you could go for custody or rights to see the child is that the family courts have a broad description on what is considered a parent. So technically even if you do a DNA test and the child is not yours but you've cared for them, you still might be up for child support.

Family Lawyer my thanks and welcome, please consider staying around, yes your point is very true and lets face it we have fathers who are not dad but happy to stay around.
BUT been around construction work and workers most of my life,, once dads hid from child support under fake names in that field.
Quite rightly the laws have changed
But too some true victims are deliberately picked out to be not the dad, it is them I talk about.
Many times broken men have spoken to me about their wages being held to pay for someone else's child, most recently such a not the dad trying to get to see children he had supported for near twelve years,was told *they are not your kids* by the mum? thoughts?

//So technically even if you do a DNA test and the child is not yours but you've cared for them, you still might be up for child support.//

So basically, you're better off just avoiding kids altogether and keeping dogs instead. Less hassle, less noise, less mess, less expense and more fun.

http://www.youtube.com/watch?v=rQ-fvr2qLc0