module ActionDispatch::Assertions::RoutingAssertions

assert_generates "changesets/12", { controller: 'scm', action: 'show_diff', revision: "12" }
# Asserts that the generated route gives us our custom route

assert_generates "/items/list/1", { controller: "items", action: "list", id: "1" }
# Tests the generation of a route with a parameter

assert_generates "/items/list", controller: "items", action: "list"
# Tests that the list action is properly routed

assert_generates "/items", controller: "items", action: "index"
# Asserts that the default action is generated for a route with no action

The +defaults+ parameter is unused.

a query string. The +message+ parameter allows you to specify a custom error message for assertion failures.
The +extras+ parameter is used to tell the request the names and values of additional request parameters that would be in
Asserts that the provided options can be used to generate the provided path. This is the inverse of +assert_recognizes+.

def assert_generates(expected_path, options, defaults = {}, extras = {}, message = nil)
  if expected_path.include?("://")
    fail_on(URI::InvalidURIError, message) do
      uri = URI.parse(expected_path)
      expected_path = uri.path.to_s.empty? ? "/" : uri.path
    end
  else
    expected_path = "/#{expected_path}" unless expected_path.start_with?("/")
  end
  options = options.clone
  generated_path, query_string_keys = @routes.generate_extras(options, defaults)
  found_extras = options.reject { |k, _| ! query_string_keys.include? k }
  msg = message || sprintf("found extras <%s>, not <%s>", found_extras, extras)
  assert_equal(extras, found_extras, msg)
  msg = message || sprintf("The generated path <%s> did not match <%s>", generated_path,
      expected_path)
  assert_equal(expected_path, generated_path, msg)
end