@johnbayne is seems that the issue is due to a change in the way truffle handles tests parallelising. The consequence is that the current way to configure provider in truffle-config.js which is displayed in our quickstart doc doesn't work for testing anymore. Long story short, with the config sample we provide, you get short on connections very fast and the provider is saturated.
I tested and was able to reproduce your issue and find a fix. We will update our quickstart for sure, but for now, you can update your truffle-config.js as indicated in https://ethereum.stackexchange.com/a/73858/405
It will require you to change it to :
Let me know if that helps.