Testing a DataTable implementation based on Ryan Bates RailsCast

datatable_spec.rb

require 'spec_helper'

describe OrderDatatable do
  describe '#initialize' do
    params = {
      :sSortDir_0 => 'asc', :iSortCol_0 => "1", :iDisplayStart => "26",
      :iDisplayLength => "50", :sSearch => "", :sEcho => "1"
    }
    let(:view) { double("view", :params => params) }
    let(:datatable) { OrderDatatable.new(view) }

    it 'receives a view as context' do
      datatable.view.should eql view
    end
  end

  describe 'delegations' do
    params = {
      :sSortDir_0 => 'asc', :iSortCol_0 => "1", :iDisplayStart => "26",
      :iDisplayLength => "50", :sSearch => "", :sEcho => "1"
    }
    let(:view) { double("view", :params => params) }
    let(:datatable) { OrderDatatable.new(view) }

    it 'delegates params call to view' do
      view.expects(:params).returns({:sEcho => 4})
      datatable.params
    end

    it 'delegates h call to view' do
      view.expects(:h).returns('foo')
      datatable.h
    end

    it 'delegates link_to to view' do
      view.expects(:link_to).returns('foo')
      datatable.link_to
    end

    it 'delegates number_to_currency to view' do
      view.expects(:number_to_currency).returns('foo')
      datatable.number_to_currency
    end
  end

  describe '#as_json' do
    params = {
      :sSortDir_0 => 'asc', :iSortCol_0 => "1", :iDisplayStart => "26",
      :iDisplayLength => "50", :sSearch => "", :sEcho => "1"
    }
    let(:view) { double("view", :params => params) }
    let(:datatable) { OrderDatatable.new(view) }

    it 'returns a json hash' do
      datatable.as_json.should be_a Hash
    end

    it 'has jquery.dataTables required keys' do
      datatable.as_json.keys.should include(:sEcho, :iTotalRecords, :iTotalDisplayRecords, :aaData)
    end
  end

  context 'helper methods' do
    params = {
      :sSortDir_0 => 'asc', :iSortCol_0 => "1", :iDisplayStart => "26",
      :iDisplayLength => "50", :sSearch => "", :sEcho => "1"
    }
    let(:view) { double("view", :params => params) }
    let(:datatable) { OrderDatatable.new(view) }

    describe '#sort_direction' do
      it 'returns the value of params[:sSortDir_0]' do
        datatable.send(:sort_direction).should eql view.params[:sSortDir_0]
        datatable.send(:sort_direction).should be_a String
      end
    end

    describe '#sort_column' do
      it 'returns value of params[:iSortCol_0]' do
        datatable.send(:sort_column).should be_a String
      end
    end

    describe '#page' do
      it 'returns an integer that represents a page number from pagination' do
        datatable.send(:page).should be_a Integer
      end
    end

    describe '#per_page' do
      it 'returns the value of params[:iDisplayLength] converted to Integer' do
        datatable.send(:per_page).should eql 50
      end

      it 'defaults to 25 if value is not provided or equal to 0' do
        view.stubs(:params).returns({ :iDisplayLength => "0" })
        datatable.send(:per_page).should eql 25

        view.stubs(:params).returns({ :iDisplayLength => "" })
        datatable.send(:per_page).should eql 25
      end
    end

    describe '#fetch_orders' do
      before :each do
        Order.should_receive(:where).with(any_args()).at_least(:once)
      end

      it 'returns an ActiveRecord::Relation of Order objects' do
        datatable.send(:fetch_orders).should be_a ActiveRecord::Relation
      end

      it 'calls private methods :sort_column and :sort_direction' do
        datatable.should_receive(:sort_column)
        datatable.should_receive(:sort_direction)
        datatable.send(:fetch_orders)
      end

      it 'calls private methods :page and :per_page' do
        datatable.should_receive(:per_page)
        datatable.should_receive(:page)
        datatable.send(:fetch_orders)
      end

      it 'performs search on :id, :purchased_at, :account, :transaction_id, :total columns' do
        view.stubs(:params).returns({ :sSearch => "1234" })
        datatable.send(:fetch_orders)
      end
    end

    describe '#orders' do
      it 'calls :fetch_orders the first time' do
        datatable.should_receive(:fetch_orders)
        datatable.send(:orders)
      end

      it 'caches the value and does not call :fetch_orders if nothing changed' do
        datatable.send(:orders)
        datatable.should_not_receive(:fetch_orders)
        datatable.send(:orders)
      end
    end

    describe '#data' do
      it 'returns an Array' do
        datatable.send(:data).should be_a Array
      end
    end
  end
end