Validate event end time is after start time

app/models/event.rb

@@ -6,6 +6,7 @@ class Event < ApplicationRecord
   validates :name, presence: true
   validates :group, presence: true
   validates :foursquare_venue_id, presence: true
+  validate :end_at_cannot_be_before_start_at
 
   scope :future_or_now, -> { where("end_at >= ?", Time.current).order(:start_at) }
   scope :past, -> { where("end_at < ?", Time.current).order(start_at: :desc) }
@@ -29,6 +30,10 @@ def formatted_local_time
 
   private
 
+  def end_at_cannot_be_before_start_at
+    errors.add(:end_at, "can't be before start_at") if end_at && start_at && end_at <= start_at
+  end
+
   def ensure_updated_foursquare_venue_data
     if new_record?
       EventVenueHydrator.run(self)

spec/models/event_spec.rb

@@ -9,6 +9,16 @@
   it { is_expected.to validate_presence_of(:group) }
   it { is_expected.to validate_presence_of(:foursquare_venue_id) }
 
+  describe "validate" do
+    describe "#end_at_cannot_be_before_start_at" do
+      it "validates end at is after start at" do
+        event = build(:event, start_at: Time.current, end_at: Time.current.yesterday)
+        expect(event).not_to be_valid
+        expect(event.errors[:end_at]).to eq(["can't be before start_at"])
+      end
+    end
+  end
+
   describe ".future_or_now" do
     it "returns all future events" do
       events = create_list(:future_event, 3)

spec/system/group_details_spec.rb

@@ -57,8 +57,8 @@
 
       it "orders past events with the most recent at the top", vcr: { cassette_name: :foursquare_venue_details } do
         group = create(:group)
-        create(:past_event, group: group, name: "Old Name", start_at: group.created_at - 1.second)
-        create(:past_event, group: group, name: "More Recent Name", start_at: group.created_at + 1.second)
+        create(:past_event, group: group, name: "Old Name", start_at: group.created_at - 1.second, end_at: group.created_at)
+        create(:past_event, group: group, name: "More Recent Name", start_at: group.created_at + 1.second, end_at: group.created_at + 2.seconds)
         visit group_path(group)
         expect(page.body.index("More Recent Name")).to be < page.body.index("Old Name")
       end