Revert "Add test to make sure this method will not be removed again"

This reverts commit d93a5d385e5bc2392a1f47dc2885e353898b62e1.

Revert "Revert "Remove unused internal methods in ActiveModel::Attributes""

This reverts commit 2d7967204e7f7d5ba846b0a6ed51088c7a7db365.

Reason: read_attribute was added in 6.1 as a performance optimization
and it is not needed anymore and write_attribute only existed to make
possible to call something that is not `attribute=` with send. We don't
need those methods internally and since they were never part of the
public API we can remove them.

activemodel/lib/active_model/attributes.rb

@@ -120,27 +120,11 @@ def freeze
     end
 
     private
-      # Writes a value to an attribute by name following aliases if necessary.
-      def write_attribute(attr_name, value)
-        name = attr_name.to_s
-        name = self.class.attribute_aliases[name] || name
-
-        @attributes.write_from_user(name, value)
-      end
-
       def _write_attribute(attr_name, value)
         @attributes.write_from_user(attr_name, value)
       end
       alias :attribute= :_write_attribute
 
-      # Reads a value from an attribute by name following aliases if necessary.
-      def read_attribute(attr_name)
-        name = attr_name.to_s
-        name = self.class.attribute_aliases[name] || name
-
-        @attributes.fetch_value(name)
-      end
-
       def attribute(attr_name)
         @attributes.fetch_value(attr_name)
       end

activemodel/test/cases/attributes_test.rb

@@ -14,19 +14,6 @@ class ModelForAttributesTest
       attribute :string_with_default, :string, default: "default string"
       attribute :date_field, :date, default: -> { Date.new(2016, 1, 1) }
       attribute :boolean_field, :boolean
-
-      alias_attribute :integer, :integer_field
-      alias_attribute :string, :string_field
-
-      def method_that_writes_to_an_attribute
-        value = read_attribute(:integer_field)
-        write_attribute(:string_field, value.to_s)
-      end
-
-      def method_that_writes_to_an_attribute_using_aliases
-        value = read_attribute(:integer)
-        write_attribute(:string, value.to_s)
-      end
     end
 
     class ChildModelForAttributesTest < ModelForAttributesTest
@@ -142,19 +129,5 @@ class GrandchildModelForAttributesTest < ChildModelForAttributesTest
       assert data.frozen?
       assert_raise(FrozenError) { data.integer_field = 1 }
     end
-
-    test "attributes can be read and written using the public API" do
-      data = ModelForAttributesTest.new(integer_field: 20)
-      data.method_that_writes_to_an_attribute
-
-      assert_equal "20", data.string_field
-    end
-
-    test "attributes can be read and written using the public API even with aliases" do
-      data = ModelForAttributesTest.new(integer: 20)
-      data.method_that_writes_to_an_attribute
-
-      assert_equal "20", data.string
-    end
   end
 end