In Rails 5.0, migration classes changed so that they were versioned:
instead of inheriting from `ActiveRecord::Migration`, you inherited from
`ActiveRecord::Migration[5.0]`. The old way wasn't removed, however --
that is, until Rails 5.1. Hence, our acceptance tests that use the old
style no longer work under the 5.1 Appraisal.
* It changes shoulda-matchers to allow the integration with multiple
libraries like active_model and active_record.
For example, in a non Rails project isn't possible to use both
validate_presence_of and validate_uniqueness_of matchers, because they
are from different libraries (one from active_model and the other from
active_record respectively).
This change allow the integration with multiple libraries. fixes#710
When running tests, you can now switch between running them against a
SQLite or PostgreSQL database. This is accomplished by modifying the
unit and acceptance tests so that when they generate and load the test
Rails application, database.yml is replaced with content that will
configure the database appropriately.
Igor Zubkov