First.. You're in Detroit and you're having a hard time finding H? Hmmm... If you want good H, the best way to get it is to hit the street and bend some corners.. That will score you the best stuff until you get a solid phone connect, but it's also very dangerous. Heroin is a dangerous game to play.
Pretending that you know what you're talking about will certainly help though. H dealers love to take advantage of people with little experience.
However, I do NOT recommend trying to be a "tester". Not only will you fuck up this person's batch, but you could end up killing yourself.
In my experience, being a tester involves sitting down with your dealer while they cut their product, and testing out little bits at a time. Although it's usually done by injection, I know some people who would let people try snorting it as well. But this usually involves doing a LOT of dope, and if you don't have the tolerance this person is expecting you to have, the first toot could be too strong and end up killing you.
Even the best outcome involves you telling her it's strong enough, and she quits cutting and bags it up, and then her customers get incredibly pissed off when they realize how weak it is.
So I don't recommend testing, not at all.. But yeah, learning the lingo isn't bad. Although telling her you're dope sick might not work the best.. A whole lot of stuff goes along with that. For starters, if you're sick and not begging and bugging the shit out of her, that right there can get suspicious. Also, you're gonna need to look sick. You can't really hide being dope sick, it's always pretty obvious.
And if you told her on this first day that you're sick, and she doesn't have dope for a few days, you might need a story prepared about how you made it through the past couple of days.
Either way, be careful, please. If you have an addictive personality, be extra careful. I finally quit heroin after a 5 year IV addiction that nearly killed me several times. Heroin isn't a drug, it's a lifestyle choice.