How to create an isolated ActiveRecord connection for testing without breaking the rest of the suite.

duration_spec.rb

require "active_record"
require "lib/duration"

class Event < ActiveRecord::Base
  include Duration
end

describe Duration do
  before do
    ActiveRecord::Base.establish_connection(
      :adapter => "sqlite3",
      :database => ":memory:")

    ActiveRecord::Base.connection.create_table(:events) do |t|
      t.datetime :start_at
      t.datetime :end_at
    end
  end

  # Return to your regularly scheduled testing
  after :all do
    if ActiveRecord::Base.configurations['test']
      ActiveRecord::Base.establish_connection :test
    end
  end

  describe "started/not_started" do
    it "should return events with past start_at" do
      event = Event.create :start_at => 1.day.ago
      Event.started.should == [event]
      Event.not_started.should == []
    end

    it "should not return events with future start_at" do
      event = Event.create :start_at => 1.day.from_now
      Event.started.should == []
      Event.not_started.should == [event]
    end
  end

  describe "ended/not_ended" do
    it "should return events with past end_at" do
      event = Event.create :start_at => 1.day.ago,
                           :end_at => 1.day.ago
      Event.started.should == [event]
      Event.not_started.should == []
    end

    it "should not return events with future end_at" do
      event = Event.create :start_at => 1.day.ago,
                           :end_at => 1.day.from_now
      Event.started.should == [event]
      Event.not_started.should == []
    end
  end

  describe "current" do
    it "should return event that are started and not ended" do
      event = Event.create :start_at => 1.day.ago,
                           :end_at => 1.day.from_now
      Event.current.should == [event]
    end
  end
end