Swap SKILL.md example to ActionController::TestRequest.new/create

Rails 4.2 → 5.0 case where `TestRequest.new` arity changes and `.create`
is 5.0-only — each side raises on the other. Clearer two-sided example
than `ignorable` → `ignored_columns=` (kept in references/code-patterns).

Author: JuanVqz

README.md

@@ -71,14 +71,13 @@ In Claude Code, navigate to your Rails application directory and use natural lan
 When writing code that must work with two versions, always use `NextRails.next?`:
 
 ```ruby
-# app/models/project.rb
-class Project < ActiveRecord::Base
+# spec/requests/projects_spec.rb
+test_request =
   if NextRails.next?
-    self.ignored_columns += [:category]
+    ActionController::TestRequest.create
   else
-    ignore_columns :category
+    ActionController::TestRequest.new
   end
-end
 ```
 
 Never use `respond_to?`, `defined?`, or other feature-detection patterns. They are fragile, hard to clean up, and obscure intent.

dual-boot/CHANGELOG.md

@@ -1,7 +1,8 @@
 # Changelog
 
-## v1.1 — 22 April 2026
-- Replaced the `fixture_path`/`fixture_paths` and `serialize coder:` examples (both backwards-compat deprecations that don't require a conditional) with a genuine breaking change: `ignorable` gem's `ignore_columns` → native `ignored_columns=` at Rails 4.2 → 5.0, where each side's API raises `NoMethodError` on the other. (#2)
+## v1.1 — 24 April 2026
+- Swapped the canonical NextRails.next? example across the skill to `ActionController::TestRequest.new` → `TestRequest.create` at Rails 4.2 → 5.0: `new` takes optional `env` on 4.2 but requires 2 non-optional args on 5.0, and `create` doesn't exist on 4.2 — each side raises on the other. Updated SKILL.md, README.md, `references/code-patterns.md`, `workflows/cleanup-workflow.md`, and `examples/basic-setup.md`.
+- Previously replaced the `fixture_path`/`fixture_paths` and `serialize coder:` examples (both backwards-compat deprecations that don't require a conditional) with a genuine breaking change. (#2)
 - Added a new "When NOT to Branch: Deprecations" section in `references/code-patterns.md` using `fixture_path` → `fixture_paths` as the counter-example, so readers learn that deprecations are unconditional migrations — not `NextRails.next?` conditionals.
 - Broadened the "no feature detection" rule to call out `defined?` and `const_defined?` alongside `respond_to?`.
 - Standardized on `NextRails.next?` polarity across the skill (removed the "`.current?` is also fine" clause from `CLAUDE.md`).

dual-boot/SKILL.md

@@ -50,26 +50,25 @@ Reach for `NextRails.next?` only when the old and new APIs are genuinely **two-s
 
 ❌ **WRONG — Do NOT use feature detection (`respond_to?`, `defined?`, etc.):**
 ```ruby
-if Project.respond_to?(:ignored_columns=)
-  self.ignored_columns += [:category]
-else
-  ignore_columns :category
-end
+test_request =
+  if ActionController::TestRequest.respond_to?(:create)
+    ActionController::TestRequest.create
+  else
+    ActionController::TestRequest.new
+  end
 ```
 
 ✅ **CORRECT — Use `NextRails.next?`:**
 ```ruby
-# app/models/project.rb
-class Project < ActiveRecord::Base
+test_request =
   if NextRails.next?
-    self.ignored_columns += [:category]
+    ActionController::TestRequest.create
   else
-    ignore_columns :category
+    ActionController::TestRequest.new
   end
-end
 ```
 
-This is a genuine two-sided case (Rails 4.2 → 5.0): on 4.2 the app uses the [`ignorable`](https://github.com/nthj/ignorable) gem's `ignore_columns` class method. Rails 5.0 introduced native `ignored_columns=` with different syntax, and once the gem is dropped on the 5.0 side, `ignore_columns` raises `NoMethodError`. `ignored_columns=` raises `NoMethodError` on 4.2 where it doesn't yet exist.
+This is a genuine two-sided case (Rails 4.2 → 5.0). On 4.2, [`ActionController::TestRequest.new`](https://github.com/rails/rails/blob/11f2bdf75a888682b34df0f9be03b94f54fc6796/actionpack/lib/action_controller/test_case.rb#L201) takes an optional `env`; on 5.0 `new` [requires two non-optional arguments](https://github.com/rails/rails/blob/c4d3e202e10ae627b3b9c34498afb45450652421/actionpack/lib/action_controller/test_case.rb#L48) so the 4.2 call fails. Rails 5.0 introduces `TestRequest.create`, which does not exist on 4.2 — so each side raises on the other.
 
 Put the next-version branch on top so cleanup is mechanical: after the upgrade, keep the `if` body and drop the `else`. See `references/code-patterns.md` for more examples.
 

dual-boot/examples/basic-setup.md

@@ -26,8 +26,6 @@ next_rails --init
 
 ### 3. Configure Gemfile
 
-If your 4.2 app already depends on a gem that needs dropping on the 5.0 side (the `ignorable` gem in this example), move it from the Gemfile root into the `else` branch so it's installed only for Rails 4.2.
-
 ```ruby
 # Gemfile
 
@@ -41,7 +39,6 @@ if next?
   gem 'rails', '~> 5.0.0'
 else
   gem 'rails', '~> 4.2.0'
-  gem 'ignorable' # used for `ignore_columns` on 4.2; dropped on 5.0
 end
 
 gem 'next_rails'
@@ -72,17 +69,16 @@ BUNDLE_GEMFILE=Gemfile.next bundle exec rspec
 
 ### 6. Fix a Breaking Change
 
-Rails 5.0 introduced a native `ignored_columns=` setter, replacing the `ignorable` gem's `ignore_columns` class method. With the gem dropped on the 5.0 side, `ignore_columns` raises `NoMethodError` there; `ignored_columns=` raises `NoMethodError` on 4.2 where it doesn't yet exist. A conditional is required:
+On Rails 4.2, `ActionController::TestRequest.new` takes an optional `env`. On 5.0, `new` requires two non-optional arguments (so the 4.2 call raises `ArgumentError`), and 5.0 introduces `TestRequest.create` — which doesn't exist on 4.2 (`NoMethodError`). Each side raises on the other. A conditional is required:
 
 ```ruby
-# app/models/project.rb
-class Project < ActiveRecord::Base
+# spec/requests/projects_spec.rb
+test_request =
   if NextRails.next?
-    self.ignored_columns += [:category]
+    ActionController::TestRequest.create
   else
-    ignore_columns :category
+    ActionController::TestRequest.new
   end
-end
 ```
 
 ### 7. Verify Both Pass
@@ -95,7 +91,7 @@ BUNDLE_GEMFILE=Gemfile.next bundle exec rspec  # Next: green
 ### 8. Commit
 
 ```bash
-git add Gemfile Gemfile.next Gemfile.next.lock app/models/project.rb
+git add Gemfile Gemfile.next Gemfile.next.lock spec/requests/projects_spec.rb
 git commit -m "Set up dual-boot for Rails 4.2 → 5.0 upgrade"
 ```
 
@@ -106,19 +102,16 @@ git commit -m "Set up dual-boot for Rails 4.2 → 5.0 upgrade"
 Once you're fully on Rails 5.0, clean up:
 
 ```ruby
-# app/models/project.rb — BEFORE cleanup
-class Project < ActiveRecord::Base
+# spec/requests/projects_spec.rb — BEFORE cleanup
+test_request =
   if NextRails.next?
-    self.ignored_columns += [:category]
+    ActionController::TestRequest.create
   else
-    ignore_columns :category
+    ActionController::TestRequest.new
   end
-end
 
-# app/models/project.rb — AFTER cleanup
-class Project < ActiveRecord::Base
-  self.ignored_columns += [:category]
-end
+# spec/requests/projects_spec.rb — AFTER cleanup
+test_request = ActionController::TestRequest.create
 ```
 
 See `workflows/cleanup-workflow.md` for the full cleanup process.

dual-boot/references/code-patterns.md

@@ -6,25 +6,23 @@ Use `NextRails.next?` anywhere your application code must behave differently bet
 
 **Only branch when the old code actually breaks on the next version.** A deprecation warning is not a reason for a conditional — if the new API works on both, replace the call site directly and let the deprecation disappear on its own. Reserve `NextRails.next?` for removed constants, removed methods, or incompatible signature/return-type changes that would raise an error otherwise.
 
-The version numbers in the example below are from a Rails 4.2 → 5.0 upgrade, but the pattern applies any time a gem-provided API is replaced by a native Rails API with different syntax (or vice versa) — the same shape works for any adjacent-version boundary where dropping the gem on one side makes the call unavailable.
+The version numbers in the example below are from a Rails 4.2 → 5.0 upgrade, but the pattern applies any time a method's signature or availability changes incompatibly across versions — the same shape works for any adjacent-version boundary where each side raises on the other's call.
 
 ---
 
 ## Rails API Changes Requiring a Conditional
 
-### `ignorable` gem → native `ignored_columns=` (Rails 4.2 → 5.0)
+### `ActionController::TestRequest.new` → `.create` (Rails 4.2 → 5.0)
 
-An app using the [`ignorable`](https://github.com/nthj/ignorable) gem to ignore columns on Rails 4.2 hits a genuine two-sided case when upgrading to 5.0, which introduced a native `ignored_columns=` with different syntax. If the gem is dropped on the 5.0 side (since Rails now has the feature), `ignore_columns :category` raises `NoMethodError` there; `self.ignored_columns += [:category]` raises `NoMethodError` on 4.2 where the setter doesn't exist yet.
+On Rails 4.2, [`ActionController::TestRequest.new`](https://github.com/rails/rails/blob/11f2bdf75a888682b34df0f9be03b94f54fc6796/actionpack/lib/action_controller/test_case.rb#L201) takes an optional `env` argument. On Rails 5.0, `new` [requires two non-optional arguments](https://github.com/rails/rails/blob/c4d3e202e10ae627b3b9c34498afb45450652421/actionpack/lib/action_controller/test_case.rb#L48), so the 4.2-style call raises `ArgumentError`. Rails 5.0 introduced `TestRequest.create` to hide that complexity — but `.create` does not exist on 4.2 (`NoMethodError`). Each side raises on the other's call.
 
 ```ruby
-# app/models/project.rb
-class Project < ActiveRecord::Base
+test_request =
   if NextRails.next?
-    self.ignored_columns += [:category]
+    ActionController::TestRequest.create
   else
-    ignore_columns :category
+    ActionController::TestRequest.new
   end
-end
 ```
 
 ---

dual-boot/workflows/cleanup-workflow.md

@@ -28,20 +28,17 @@ For each file found in Step 1, keep only the `NextRails.next?` (true) branch and
 
 ### Before:
 ```ruby
-class Project < ActiveRecord::Base
+test_request =
   if NextRails.next?
-    self.ignored_columns += [:category]
+    ActionController::TestRequest.create
   else
-    ignore_columns :category
+    ActionController::TestRequest.new
   end
-end
 ```
 
 ### After:
 ```ruby
-class Project < ActiveRecord::Base
-  self.ignored_columns += [:category]
-end
+test_request = ActionController::TestRequest.create
 ```
 
 ---