Add error on existing supplier name for current employee

spec/acceptance_steps/suppliers/signup_steps.rb

@@ -20,6 +20,10 @@ step "fill in the supplier signup form with a new supplier name" do
   js_set_field '#new_supplier_supplier_name', 'Signup Supplier'
 end
 
+step "fill in the supplier signup form with an existing supplier name" do
+  js_set_field '#new_supplier_supplier_name', @supplier.name
+end
+
 step "click on the supplier signup submit button" do
   find('[name="commit"]').click
 end
@@ -59,3 +63,7 @@ step "the new signup supplier should be confirmed" do
   @signup_supplier.reload
   @signup_supplier.should be_confirmed
 end
+
+step "the new supplier signup for should have an error on :attribute" do |attribute|
+  page.should have_selector ".#{attribute}.error"
+end