See gh-56 for an issue on this
Stop fetch from mutating when default is a hash
This line makes me uneasy. It's needed for the "sticky" tests to pass but I feel like the Parameters were permitted then we dropped new data via a default hash, which hasn't been checked. Maybe that's OK because you are in control since they are defaults?
Huge +1 This has been a really annoying bug.
@bemurphy Could you get the tests passing again?
First, we need to fix this issue on rails/rails, after this we can merge it on the gem.
I resubmitted this to rails, it's merged here: rails/rails#12656