POST to the Same Page and Verify Results in Rails

// routes.rb
get 'dev/form'
post 'dev/form'

// form.html.erb
<%= form_tag(dev_form_path, method: "post") do %>
  <%= label_tag(:q, "Search for:") %>
  <%= text_field_tag(:q) %>
  <%= submit_tag("Search") %>
<% end %>

<%= params[:q] %>

form.html.erb is POSTing to form.html.erb itself.

With this, the single page application is complete.

Since we only write this much and only use two files, it's easy to manage, right.