Stress test? Whats it for? How long does the stress test usually last on the blockchain? Also what is it for? I'm fairly new to bitcoin and was having trouble processing transactions in a fair amount of time earlier.
It's not a standard occurrence, it's just a company of dubious origin deciding that they will spam transactions to somehow prove a point about block sizes. Interestingly it proves the opposite of what they intended, rather than showing that the block size needs to be bigger, it shows that no matter how big you make the blocks people can spam enough to fill them. 

If you have trouble getting transactions confirmed, you need to pay a fee for them rather than relying on the charity of miners. A transaction paying more than an absolutely rock bottom fee will be prioritized over the spam.