pinned links should validate that their end time is not before start time

Author: Oaphi

app/models/pinned_link.rb

@@ -29,6 +29,7 @@ class PinnedLink < ApplicationRecord
     before.or(after)
   }
 
+  validate :check_period
   validate :check_post_or_url
 
   # Is the link not timed or started in the past & hasn't ended yet?
@@ -58,6 +59,14 @@ def timed?
     shown_before.present? || shown_after.present?
   end
 
+  def check_period
+    return unless shown_before.present? && shown_after.present?
+
+    if shown_before < shown_after
+      errors.add(:base, 'end date cannot be earlier than the start date')
+    end
+  end
+
   def check_post_or_url
     unless post_id.present? || link.present?
       errors.add(:base, 'either a post or a URL must be set')

test/models/pinned_link_test.rb

@@ -39,4 +39,19 @@ class PinnedLinkTest < ActiveSupport::TestCase
       assert link.future?(now)
     end
   end
+
+  test 'pinned links should be correctly validated' do
+    valid_with_link = PinnedLink.new(link: 'https://example.com')
+    valid_with_post = PinnedLink.new(post: posts(:question_one))
+    period_mismatch = PinnedLink.new(shown_before: DateTime.now - 1, shown_after: DateTime.now)
+
+    [
+      [valid_with_link, true],
+      [valid_with_post, true],
+      [period_mismatch, false]
+    ].each do |test|
+      link, status = test
+      assert_equal status, link.valid?
+    end
+  end
 end