How do I prepare test database(s) for Rails rspec tests without running rake spec?

I would recommend dropping your test database, then re-create it and migrate:

bundle exec rake db:drop RAILS_ENV=test
bundle exec rake db:create RAILS_ENV=test
bundle exec rake db:schema:load RAILS_ENV=test

After these steps you can run your specs:

bundle exec rspec spec

gerry3 noted that:

A simpler solution is to just run rake db:test:prepare

However, if you’re using PostgreSQL this wont work because the rails environment gets loaded, which opens a database connection. This causes the prepare call to fail, because the DB cannot be dropped. Tricky thing.