[#257 state:awaiting-patch] here is a test proving the issue

spec/integration/rails/app/controllers/fields_controller.rb

@@ -0,0 +1,4 @@
+class FieldsController < ApplicationController
+  def show
+  end
+end

spec/integration/rails/app/helpers/fields_helper.rb

@@ -0,0 +1,2 @@
+module FieldsHelper
+end

spec/integration/rails/app/views/fields/show.html.erb

@@ -0,0 +1,8 @@
+<h1>Webrat Fields Page</h1>
+<h2>Filling In</h2>
+<ul>
+	<li><input type="text" name="field_by_name" value="" /></li>
+	<li><input type="text" name="rails[naming]" value="" /></li>
+	<li><input type="text" id="field_by_id" value="" /></li>
+	<li><label for="field_by_label_id">FieldByLabelId</label><input type="text" id="field_by_label_id" /></li>
+</ul>

spec/integration/rails/config/routes.rb

@@ -1,6 +1,7 @@
 ActionController::Routing::Routes.draw do |map|
   map.resource 'links', :only => [:show]
   map.resource 'buttons', :only => [:show, :create]
+  map.resource 'fields', :only => [:show]
   map.with_options :controller => "webrat" do |webrat|
     webrat.submit             "/submit",            :action => "submit"
     webrat.internal_redirect  "/internal_redirect", :action => "internal_redirect"

spec/integration/rails/test/functional/buttons_controller_test.rb

@@ -1,8 +0,0 @@
-require 'test_helper'
-
-class ButtonsControllerTest < ActionController::TestCase
-  # Replace this with your real tests.
-  test "the truth" do
-    assert true
-  end
-end

spec/integration/rails/test/functional/links_controller_test.rb

@@ -1,8 +0,0 @@
-require 'test_helper'
-
-class LinksControllerTest < ActionController::TestCase
-  # Replace this with your real tests.
-  test "the truth" do
-    assert true
-  end
-end

spec/integration/rails/test/integration/fill_in_test.rb

@@ -0,0 +1,20 @@
+require 'test_helper'
+
+class FillInTest < ActionController::IntegrationTest
+  test "should fill in text field by name" do
+    visit fields_path
+    fill_in "field_by_name", :with => "value"
+  end
+  test "should fill in text field by name, rails naming lh257" do
+    visit fields_path
+    fill_in "rails[naming]", :with => "value"
+  end
+  test "should fill in text field by id" do
+    visit fields_path
+    fill_in "field_by_id", :with => "value"
+  end
+  test "should fill in text field by label via id" do
+    visit fields_path
+    fill_in "FieldByLabelId", :with => "value"
+  end
+end