Is a gem ready for Rails 4 or 5?

since gem version 1.0.0 (source)

since version 1.5.2

since gem version 3.0.0

since gem version 3.0.2

Version 3.0 is ready for Rails 4, implemented, tested.

Version 3.0 is ready for Rails 5, see comment in release notes.

from gem version 3.0.0

since gem version 4.0.0.

It works

Since 0.1.6

since 0.7.0 https://github.com/applicake/doorkeeper/blob/master/CHANGELOG.md#070

since version 4.0.0

Works fine, tested with Rails 4.

since version 2.1.0 (https://github.com/bkeepers/dotenv/blob/master/Changelog.md#210---jan-13-2016)

see readme

see readme

-

since version 3.0, see https://github.com/drapergem/draper/blob/master/CHANGELOG.md#300pre1---2016-07-10

https://github.com/lucascaton/enumerate_it/blob/master/.travis.yml#L25

https://github.com/lucascaton/enumerate_it/blob/master/.travis.yml#L26

since 4.0.0.rc1

from version 4.2.0

https://github.com/thoughtbot/factory_girl/blob/master/Appraisals#L9

since version 4.4

-

since version 4.4

In use.

does not depend on Rails

https://github.com/jhund/filterrific/blob/master/CHANGELOG.md

https://github.com/jhund/filterrific/blob/master/CHANGELOG.md

Running on our 4.2 app for some time

Not dependent on Rails

running on our 4.2 app for some time

Not dependent on rails

https://github.com/bokmann/font-awesome-rails/issues/45

since version 4.5.0.1

-

when not bundled in Gemfile. See https://github.com/ddollar/foreman/issues/688#issuecomment-326615890

says so in readme

see https://git.io/vXCdc