Better tests for AV::RecordIdentifier

This commit intends to clarify the scope of ActionView::RecordIdentifier
methods `dom_id` and `dom_class`.

Most of the current documentation comes from da257eb8 (7 years ago) when
the decoupling of ActionView, ActiveRecord and ActiveModel was not a concern.

Since then, steps have been taken to reach such decoupling.
Therefore I think it's important to show that ActionView::RecordIdentifier
**does not strictly depend on the ActiveRecord API**:
any class `Post` implementing `post.to_key` and `post.model_name.param_key`
will work.

This commit adds a test to prove that ActionView::RecordIdentifier methods
can also be used on objects that do not subclass ActiveRecord::Base.

1 files changed, 12 insertions, 0 deletions

diff --git a/actionview/test/lib/controller/fake_models.rb b/actionview/test/lib/controller/fake_models.rb
index cb02a56cb4..789b1d198b 100644
--- a/actionview/test/lib/controller/fake_models.rb
+++ b/actionview/test/lib/controller/fake_models.rb
@@ -170,3 +170,15 @@ end
 
 class Car < Struct.new(:color)
 end
+
+class Plane
+  attr_reader :to_key
+
+  def model_name
+    OpenStruct.new param_key: 'airplane'
+  end
+
+  def save
+    @to_key = [1]
+  end
+end