Refactor confirmation matcher

This is part of a collection of commits that aim to improve failure
messages across the board, in order to make matchers easier to debug
when something goes wrong.

* Make the description of the matcher more readable.

lib/shoulda/matchers/active_model/validate_confirmation_of_matcher.rb

@@ -83,22 +83,17 @@ module Shoulda
         attr_reader :attribute, :confirmation_attribute
 
         def initialize(attribute)
-          super(attribute)
+          super
+          @expected_message = :confirmation
           @confirmation_attribute = "#{attribute}_confirmation"
         end
 
-        def with_message(message)
-          @message = message if message
-          self
-        end
-
-        def description
-          "require #{@confirmation_attribute} to match #{@attribute}"
+        def simple_description
+          "validate that #{@confirmation_attribute} matches #{@attribute}"
         end
 
         def matches?(subject)
           super(subject)
-          @message ||= :confirmation
 
           disallows_different_value &&
             allows_same_value &&
@@ -109,6 +104,7 @@ module Shoulda
 
         def disallows_different_value
           set_confirmation('some value')
+
           disallows_value_of('different value') do |matcher|
             qualify_matcher(matcher)
           end
@@ -116,6 +112,7 @@ module Shoulda
 
         def allows_same_value
           set_confirmation('same value')
+
           allows_value_of('same value') do |matcher|
             qualify_matcher(matcher)
           end
@@ -123,13 +120,15 @@ module Shoulda
 
         def allows_missing_confirmation
           set_confirmation(nil)
+
           allows_value_of('any value') do |matcher|
             qualify_matcher(matcher)
           end
         end
 
         def qualify_matcher(matcher)
-          matcher.with_message(@message,
+          matcher.with_message(
+            @expected_message,
             against: confirmation_attribute,
             values: { attribute: attribute }
           )
@@ -137,6 +136,7 @@ module Shoulda
 
         def set_confirmation(val)
           setter = :"#{@confirmation_attribute}="
+
           if @subject.respond_to?(setter)
             @subject.__send__(setter, val)
           end

spec/unit/shoulda/matchers/active_model/validate_confirmation_of_matcher_spec.rb

@@ -6,7 +6,7 @@ describe Shoulda::Matchers::ActiveModel::ValidateConfirmationOfMatcher, type: :m
   context '#description' do
     it 'states that the confirmation must match its base attribute' do
       builder = builder_for_record_validating_confirmation
-      message = "require #{builder.confirmation_attribute} to match #{builder.attribute_to_confirm}"
+      message = "validate that #{builder.confirmation_attribute} matches #{builder.attribute_to_confirm}"
       matcher = described_class.new(builder.attribute_to_confirm)
       expect(matcher.description).to eq(message)
     end