There should be "Trial / test submission" quota.

I've already subscribed for a year. 
I think that is a little bit on the shady and sneaky side to expect customers to be ok with being charged against the quota when forms are still being developed. 
You guys know the effort it takes to create these things and while your product makes it easier there's still the need to test which could easily consumed ones quota. there should be a "development quota"  extended to free developers from losing access to the forms because of overage.
I'm creating several forms on my site, and this being my first foray into jot form you have to expect lots of trial and errors. So i now have the additional exercise to watch my testing because I'm near exceeding my quota, which if i do do reach it, I'll either be useless or forced to upgrade to a more expensive plan- 
so maybe that is the plan with these limits.
Got it! 
Sent via the Samsung Galaxy Note® 3, an AT&T 4G LTE smartphone

I understand what you mean, but please do note that you can have over 100 regular submissions per month on the free plan, allowing you to set it all up and test out.

Basically when you just create your account, you have 100 submissions. While setting it all up, you should use these (regular submissions).

Once you have it all set up, you can simply switch over to using the HTTPS (secure submissions).

If you need even more than 100 submissions, it becomes easy to use the Get More option and do just that - get more.

Doing so will allow you to quickly go from 100 per month to over 250 per month each month - allowing you to do your own tests.

Please do also note that we do not make any charges towards you - you need to create the subscription on your own - if that is what you desire.

I do hope that the above is of help and that the get more option will allow you to do your own tests without any issues.