WA-NEW-004: Fix metrics week calculations across DST

core/app/models/workarea/metrics/by_week.rb

@@ -13,9 +13,14 @@ module ByWeek
         index({ reporting_on: 1 }, { expire_after_seconds: 2.years.seconds.to_i })
 
         scope :last_week, -> do
+          # Use date math to avoid DST-related boundary shifts.
+          # We want the previous calendar week, not "now minus 7 days".
+          start_of_this_week = Time.current.to_date.beginning_of_week
+          start_of_last_week = start_of_this_week - 1.week
+
           where(
-            :reporting_on.gte => Time.current.last_week,
-            :reporting_on.lt => Time.current.last_week.end_of_week
+            :reporting_on.gte => start_of_last_week.in_time_zone,
+            :reporting_on.lt => start_of_this_week.in_time_zone
           )
         end
       end

core/app/models/workarea/metrics/scoring.rb

@@ -22,8 +22,12 @@ def score(field)
       end
 
       def weeks_ago
-        difference = Time.current.beginning_of_week - reporting_on.beginning_of_week
-        difference / 1.week
+        # Use date math instead of second-based math to avoid DST boundary issues.
+        # (e.g. a "week" containing a DST shift is not always 7 * 24 hours)
+        current_week = Time.current.to_date.beginning_of_week
+        reporting_week = reporting_on.to_date.beginning_of_week
+
+        ((current_week - reporting_week) / 7).to_i
       end
     end
   end

core/test/models/workarea/metrics/product_by_week_test.rb

@@ -3,6 +3,10 @@
 module Workarea
   module Metrics
     class ProductByWeekTest < TestCase
+      setup do
+        Metrics::ProductByWeek.delete_all
+        Metrics::ProductForLastWeek.delete_all
+      end
       def test_last_week
         two_weeks_ago = create_product_by_week(reporting_on: Time.zone.local(2018, 11, 25))
         last_week = create_product_by_week(reporting_on: Time.zone.local(2018, 12, 2))
@@ -117,20 +121,34 @@ def test_score
       def test_weeks_ago
         model = create_product_by_week(reporting_on: Time.zone.local(2019, 1, 25))
 
-        travel_to Time.zone.local(2019, 1, 25)
-        assert_equal(0, model.weeks_ago)
+        travel_to Time.zone.local(2019, 1, 25) do
+          assert_equal(0, model.weeks_ago)
+        end
+
+        travel_to Time.zone.local(2019, 1, 27) do
+          assert_equal(0, model.weeks_ago)
+        end
+
+        travel_to Time.zone.local(2019, 2, 8) do
+          assert_equal(2, model.weeks_ago)
+        end
 
-        travel_to Time.zone.local(2019, 1, 27)
-        assert_equal(0, model.weeks_ago)
+        travel_to Time.zone.local(2019, 2, 9) do
+          assert_equal(2, model.weeks_ago)
+        end
 
-        travel_to Time.zone.local(2019, 2, 8)
-        assert_equal(2, model.weeks_ago)
+        travel_to Time.zone.local(2019, 2, 11) do
+          assert_equal(3, model.weeks_ago)
+        end
 
-        travel_to Time.zone.local(2019, 2, 9)
-        assert_equal(2, model.weeks_ago)
+        # Regression: DST boundaries should not affect week math.
+        Time.use_zone('Eastern Time (US & Canada)') do
+          dst_model = create_product_by_week(reporting_on: Time.zone.local(2019, 3, 4, 0, 0, 0))
 
-        travel_to Time.zone.local(2019, 2, 11)
-        assert_equal(3, model.weeks_ago)
+          travel_to Time.zone.local(2019, 3, 11, 0, 0, 0) do
+            assert_equal(1, dst_model.weeks_ago)
+          end
+        end
       end
     end
   end