Ask HN : How can i politely ask tech community to test my new web project?

I think it's fine to submit it to a site like HN.

Please don't send random emails / Twitter messages. Even if you don't think it's spam - the other person certainly will. I get dozens of messages a week saying that someone has "carefully selected me to take part in their beta."

Invite your friends - then get them to invite their friends.

Sometimes you have to hustle to make it. If you just sit back and other guy is hustling I know who I would bet on.

To quote Tinie Tempah:

I used to be the kid that no one cared about Thats why you have to keep screaming til they hear you out

Some good ideas here: http://nathanbarry.com/launch/

Create a product that you think people will like. In that way they will play with your app even if you don't ask them to do so. Provided it's good enough, early adopters will provide you feedback, which is what you want in the first place.