added more parts for the first scenario and updated code to work with the changes

features/step_definitions/steps.rb

@@ -1,7 +1,7 @@
 # GIVEN
 
 Given('I visit the homepage') do
-    visit '/'
+  visit '/'
 end
 
 # WHEN
@@ -10,6 +10,14 @@ end
 
 # THEN
 
-Then('I should see {string}') do |string|
-    page.should have_content "URL Shortener"
+Then('I should see text {string}') do |string|
+  page.should have_content string
+end
+
+Then('I should see a form field {string}') do |string|
+  page.should have_field string
+end
+
+Then('I should see a {string} button') do |string|
+  page.should have_button string
 end