Send rspec approval failures to rspec for diffing

[jeremyruppel]

Hey @kytrinyx, I thought it might be nice to have approval failures automatically show a diff in rspec. Let me know what you think!

[kytrinyx]

I implemented this at first, and then removed it, because if even one of the failing specs is not the approval, then it's a pain to page through all the approval output (typically dozens to hundreds of lines) to find the error message.

[kytrinyx]

@jeremyruppel Have you used the library much over the past 8 months? Do you still think that it would be worth having the diff in rspec?

I'd be interested in having the discussion again, if you're up for it :)

[bmarini]

@kytrinyx I've been using it pretty heavily to test json output for an API (usually pretty small chunks, 10-20 lines of json), and having a diff would be really nice. Especially when a spec fails on your CI server but not locally, where there is not an easy way to see what the diff is.

[bmarini]

Incidentally @jeremyruppel is my buddy and he is one who introduced me to the gem :)

[kytrinyx]

Cool! So how about an option that could be passed to the approval to turn the diff off in certain cases? (I sometimes use this for characterization tests of massive, legacy HTML pages).

Approvals.verify(your_subject, :format => :html, :inspect => false) # or :diff, or :show_diff or something

[jeremyruppel]

@kytrinyx @bmarini heya! Sorry for taking so long to get back to this. I definitely agree about making diffs optional. My only concern is that the diffs are dependent on RSpec and only available through the DSL in this implementation. It could make sense as an RSpec config, but that kind of implies the configuration for the whole test suite (which doesn't sound like it fits @kytrinyx's use case, amirite?). We could control it with RSpec metadata, but that feels way less intuitive to me as we're already passing our options to verify.

Hrm.

[kytrinyx]

I was thinking of making it configurable on a test-by-test basis, but I'd be fine with having it be a global-for-rspec config as a first pass.

Want to take a stab at that in this pull request? Or would you rather just pull this in and then add the config option if it becomes too obnoxious?

[jeremyruppel]

Okay! Diffs are now off by default and can be configured either for the whole suite or per-example using metadata.

[bmarini]

I like it!

[kytrinyx]

Thank you so much for the contribution, and I apologise for taking forever about it.