Do testnet networks require the same main network fee? As in the title, I'm wondering if testnet networks always require the same fee. 

I know the coins aren't worth any thing, so it doesn't matter if I have to pay the fee or not, but I'm just curious.
I would say so. I can't find any code that make fees lower or optional for testnet users. 

However, it's substantially easier to send a free transaction.

inline bool AllowFree(double dPriority)
{
    // Large (in bytes) low-priority (new, small-coin) transactions
    // need a fee.
    return dPriority &gt; COIN * 144 / 250;
}


dPriority is higher for larger amounts. Testnet coins are worth much less, so you're more likely to send lots of them around. For example, if you sent 50 testnet coins half an hour after you got them, that would be eligible for a free transaction.