Add missing specs for Tracks, Halls and Slots

Document the behaviour of Tracks, Slots and Halls with specs. Leave the
association between slots and events pending for now.

spec/factories/slots.rb

@@ -0,0 +1,9 @@
+# Read about factories at https://github.com/thoughtbot/factory_girl
+
+FactoryGirl.define do
+  factory :slot do
+    starts_at { Time.now }
+    ends_at { Time.now + 45.minutes }
+    hall
+  end
+end

spec/models/hall_spec.rb

@@ -0,0 +1,24 @@
+require 'rails_helper'
+
+RSpec.describe Hall, :type => :model do
+  it 'is invalid without a name' do
+    expect(build(:hall, name: '')).to have_error_on :name
+  end
+
+  it 'belongs to a conference' do
+    conference = create :conference
+    expect(build(:hall, conference_id: conference.id).conference).to eq conference
+  end
+
+  it 'has many slots' do
+    hall = create :hall
+    slot = create :slot, hall: hall
+    expect(hall.slots).to include slot
+  end
+
+  it 'destroys all associated slots when destroyed' do
+    hall = create :hall
+    create :slot, hall: hall
+    expect { hall.destroy }.to change { Slot.count }.by(-1)
+  end
+end

spec/models/slot_spec.rb

@@ -0,0 +1,14 @@
+require 'rails_helper'
+
+RSpec.describe Slot, :type => :model do
+  it 'belongs to a hall' do
+    hall = create :hall
+    expect(build(:slot, hall_id: hall.id).hall).to eq hall
+  end
+
+  it 'belongs to an event' do
+    pending 'Events not implemented'
+    event = create :event
+    expect(build(:slot, event_id: event.id).event).to eq event
+  end
+end

spec/models/track_spec.rb

@@ -16,4 +16,9 @@ RSpec.describe Track, :type => :model do
       expect(build(:track, color: '#000000')).to_not have_error_on :color
     end
   end
+
+  it 'belongs to a conference' do
+    conference = create :conference
+    expect(build(:track, conference_id: conference.id).conference).to eq conference
+  end
 end