モデル間のリレーションSpecを書きたくないので自動生成してみる ref: http://qiita.com/EastResident/items/e97632074f50d2541547

customer.rb

class Customer < ApplicationRecord
  has_many :orders, dependent: :destroy
end

customer_spec.rb

RSpec.describe Customer, type: :model, relation_specs: true do
end
# 下記のコードが実行されるのと同じ
# RSpec.describe Customer, type: :model do
#   describe 'association' do
#     describe 'has_many' do
#       it { is_expected.to have_many(:orders).dependent(:destroy) }
#     end
#   end
# end

model_spec.rb

require 'erb'

module AutoSpec
  module ModelSpec
    def exe_relation_specs
      @klass = Object.const_get(to_s.split('::').last.split('_').first)
      temp = open("#{File.expand_path('..', __FILE__)}/templates/relations.erb") do |f|
        ERB.new(f.read).result(binding)
      end
      instance_eval temp
    end
  end
end

order.rb

class Order < ApplicationRecord
  belongs_to :customer
end

order_spec.rb

RSpec.describe Order, type: :model, relation_specs: true do
end
# 下記のコードが実行されるのと同じ
# RSpec.describe Order, type: :model do
#   describe 'association' do
#     describe 'belongs_to' do
#       it { is_expected.to belong_to(:customer) }
#     end
#   end
# end

relation_contexts.rb

shared_context :relation_specs, relation_specs: true do
  extend AutoSpec::ModelSpec
  exe_relation_specs
end

relations.erb

<% if @klass.reflect_on_all_associations %>describe 'relation' do
  <% if (ass = @klass.reflect_on_all_associations(:has_one)).present? %>context 'has_one' do
    <% ass.each do |as| %>
    it { is_expected.to have_one(:<%= as.name %>)<%= as.options.reduce([]) { |a, e| a << (%w(foreign_key primary_key).include?(e[0].to_s) ? "\.with_#{e[0]}(:#{e[1]})" : "\.#{e[0]}(:#{e[1]})") }.join %> }<% end %>
  end<% end %>
  <% if (ass = @klass.reflect_on_all_associations(:has_many)).present? %>context 'has_many' do
    <% ass.each do |as| %>
    it { is_expected.to have_many(:<%= as.name %>)<%= as.options.reduce([]) { |a, e| a << (%w(foreign_key primary_key).include?(e[0].to_s) ? "\.with_#{e[0]}(:#{e[1]})" : "\.#{e[0]}(:#{e[1]})") }.join %> }<% end %>
  end<% end %>
  <% if (ass = @klass.reflect_on_all_associations(:belongs_to)).present? %>context 'belongs_to' do
    <% ass.each do |as| %>
    it { is_expected.to belong_to(:<%= as.name %>)<%= as.options.reduce([]) { |a, e| a << (%w(foreign_key primary_key).include?(e[0].to_s) ? "\.with_#{e[0]}(:#{e[1]})" : "\.#{e[0]}(:#{e[1]})") }.join %> }<% end %>
  end<% end %>
end<% end %>