Test with Ruby 4.0

https://www.ruby-lang.org/en/news/2025/12/25/ruby-4-0-0-released/

We need to add `ostruct` as a dev dependency because it doesn't come
as a default gem with Ruby 4.0 anymore.

Author: carlosantoniodasilva

.github/workflows/test.yml

@@ -13,6 +13,7 @@ jobs:
           - gemfiles/Gemfile-rails-7-1
           - gemfiles/Gemfile-rails-7-0
         ruby:
+          - '4.0'
           - '3.4'
           - '3.3'
           - '3.2'

CHANGELOG.md

@@ -1,3 +1,7 @@
+## Unreleased
+
+* Ruby 4.0 support (no changes required)
+
 ## 0.9.0
 
 * Add support for Ruby 3.3/3.4 and Rails 7.2/8.0/8.1. (no changes required)

Gemfile.lock

@@ -67,6 +67,7 @@ GEM
     nokogiri (1.19.0)
       mini_portile2 (~> 2.8.2)
       racc (~> 1.4)
+    ostruct (0.6.3)
     pp (0.6.3)
       prettyprint
     prettyprint (0.2.0)
@@ -122,10 +123,11 @@ PLATFORMS
 DEPENDENCIES
   actionpack (~> 8.1.0)
   activemodel (~> 8.1.0)
+  ostruct
   railties (~> 8.1.0)
   rake
   rdoc
   show_for!
 
 BUNDLED WITH
-   2.6.9
+  4.0.3

show_for.gemspec

@@ -26,4 +26,6 @@ Gem::Specification.new do |s|
 
   s.add_dependency('activemodel', '>= 7.0')
   s.add_dependency('actionpack', '>= 7.0')
+
+  s.add_development_dependency('ostruct')
 end