Gotchas

ActiveRecord

• find raises an exception that if not handled, will result in controller endpoints returning 404.

• find_by! is a variant that can be used to get the same behavior of find for find_by.

database.yml

If you try to have a generic database configuration controlled by environment variables, your database actions will run twice in development.

e.g.

default: &default
  adapter: postgresql
  encoding: unicode
  pool: <%= ENV['DATABASE_POOL'] %>
  host: <%= ENV['DATABASE_HOST'] %>
  database: <%= ENV['DATABASE_NAME'] %>
  username: <%= ENV['DATABASE_USER'] %>
  password: <%= ENV['DATABASE_PASSWORD'] %>

development:
  <<: *default

test:
  <<: *default

Since Rails by default runs migrations for the test environment when you're on development , when it tries to run them the RAILS_ENV will be development so it will actually run all the database actions on the development database again.

Instead ensure that you give specific and unique names for the development and test environments:

development:
  <<: *default
  database: my_app_development

test:
  <<: *default
  database: my_app_test