[m12k]

I've worked for a while with similar scenarios of needing to integrate with systems beyond my control (e.g. Stripe, Slack, Google), and though I still don't have a good setup for it, I've come to the conclusion that a two-pronged approach would be ideal: Record/and/or stub the calls and responses from the external services so your normal tests are run entirely without external networking (like what Polly allows you to do). But also set up a server to periodically validate the responses from the external services against those that have been recorded, and alert you to any changes in their protocol/behavior. I've yet to see any middleware to tackle the latter (though granted, I haven't been looking too hard yet either)