Posted in ElasticSearch 400 error.
I'm actually seeing the same error in a controller spec. Searchkick v. 1.3.2, elasticsearch v. 2.0.0. Rails 4.2.6 & Ruby 2.2.2. I didn't set up this searchkick so I've been googling around for suggestions on the issue and this is one of few instances of the same error.
Edit: Figured it out! Elasticsearch 5+ (not the gem) renames
stored_fields, and searchkick doesn't support that in 1.3.2. I updated searchkick and it's all fine.