Best way to test creating charges with Stripe?

I'm working on a project that requires me to take payments using Stripe. I'm writing some feature tests to check that card declines are handled correctly and I'm currently using the JacobBennet/StripeTestToken to generate fake tokens. The problem is that it's slow to generate these tokens, especially when there's around 10 being generated in my test suite.

What's the best way to approach writing these tests?

Thanks.