Creates a `grant_permission_to` matcher to test Pundit policies.

pundit.rb

# spec/support/pundit.rb
# Creates a 'grant_permission_to' matcher to better test Pundit policies
# See: http://thunderboltlabs.com/blog/2013/03/27/testing-pundit-policies-with-rspec/

RSpec::Matchers.define :grant_permission_to do |action|

  match do |policy|
    policy.public_send("#{action}?")
  end

  description do
    "grant permition to #{action}"
  end

  failure_message do |policy|
    "#{policy.class} does not permit #{action} on #{policy.record} for #{policy.user.inspect}."
  end

  failure_message_when_negated do |policy|
    "#{policy.class} does not forbid #{action} on #{policy.record} for #{policy.user.inspect}."
  end

end