Today I spent quite some time on a rather hard to track down problem. I had some specs using VCR, which worked perfectly locally, but just wouldn’t run on CircleCI. In fact, it seemed like CircleCI didn’t in fact use the VCR cassettes at all, but instead make a real API call, which failed because the necessary credentials weren’t available in the environment (which was kinda the point of using VCR in the first place).

Turns out the problem lay in the combination of using the VCR setting configure_rspec_metadata! and the option core.ignorecase = true, which is standard in newer versions of Git. What happened was that at one point I changed the case of a word in a test description, which changes the auto-generated name of the folder VCR will create the cassette in. But since the folder name wasn’t changed from git’s perspective, I never realized that. So when the code was checked out on CircleCI, VCR encountered the spec with the metadata (vcr: true), but couldn’t find the cassette since the checked out folder had the wrong case. It therefore proceeded to run the spec against the live API which failed.

All in all this cost me about 1.5 hours, and I only managed to find a solution thanks to a helpful colleague and CircleCI’s option of letting you SSH into the machine the tests run on, which is how we discovered the second folder that was created.

TIL that git’s not case-sensitive. I’d rather have found out another way.