Ensure not_to.have_xxx and to.have_no_xxx error messages are identical

lib/capybara/rspec/matchers.rb

@@ -199,6 +199,32 @@ module Capybara
       end
     end
 
+    class NegatedMatcher
+      def initialize(matcher)
+        @matcher = matcher
+      end
+
+      def matches?(actual)
+        @matcher.does_not_match?(actual)
+      end
+
+      def does_not_match?(actual)
+        @matcher.matches?(actual)
+      end
+
+      def description
+        "not #{@matcher.description}"
+      end
+
+      def failure_message
+        @matcher.failure_message_when_negated
+      end
+
+      def failure_message_when_negated
+        @matcher.failure_message
+      end
+    end
+
     class BecomeClosed
       def initialize(options)
         @options = options
@@ -279,6 +305,7 @@ module Capybara
     end
     alias_method :have_content, :have_text
 
+
     def have_title(title, **options)
       HaveTitle.new(title, options)
     end
@@ -331,6 +358,13 @@ module Capybara
       HaveSelector.new(:table, locator, options, &optional_filter_block)
     end
 
+    %w(selector css xpath text title current_path link button field checked_field unchecked_field select table).each do |matcher_type|
+      define_method "have_no_#{matcher_type}" do |*args, &optional_filter_block|
+        NegatedMatcher.new(send("have_#{matcher_type}", *args, &optional_filter_block))
+      end
+    end
+    alias_method :have_no_content, :have_no_text
+
     ##
     # Wait for window to become closed.
     # @example

lib/capybara/spec/session/has_text_spec.rb

@@ -252,7 +252,7 @@ Capybara::SpecHelper.spec '#has_no_text?' do
     expect(@session).not_to have_no_text('exercitation ullamco laboris')
   end
 
-  it "should be true if the given text is not on the page" do
+  it "should be true if the given text is not on the page", :focus_ do
     @session.visit('/with_html')
     expect(@session).to have_no_text('xxxxyzzz')
     expect(@session).to have_no_text('monkey')

spec/rspec_matchers_spec.rb

@@ -16,6 +16,18 @@ RSpec.describe 'Capybara RSpec Matchers', :type => :feature do
       expect(page).to matcher
       expect { matcher.description }.not_to raise_error
     end
+
+    it "should produce the same error for .to have_no_xxx and .not_to have_xxx" do
+      visit('/with_html')
+      not_to_msg = error_msg_for { expect(page).not_to have_selector(:css, '#referrer') }
+      have_no_msg = error_msg_for { expect(page).to have_no_selector(:css, '#referrer') }
+      expect(not_to_msg).to eq have_no_msg
+
+      not_to_msg = error_msg_for { expect(page).not_to have_text('This is a test') }
+      have_no_msg = error_msg_for { expect(page).to have_no_text('This is a test') }
+      puts not_to_msg
+      expect(not_to_msg).to eq have_no_msg
+    end
   end
 
   context "after called on element" do
@@ -43,4 +55,8 @@ RSpec.describe 'Capybara RSpec Matchers', :type => :feature do
       expect { matcher.description }.not_to raise_error
     end
   end
+
+  def error_msg_for(&block)
+    expect(&block).to raise_error { |e| return e.message }
+  end
 end