TimeDuration.exceeds_gap?: Fix duration > 24 hours behaviour

Previously, the `#exceeds_gap?` method would modulo the
`later - earlier` duration against 24 hours such that no duration
exceeded 24 hours, and the resulting duration being compared was
adjusted to fit inside a single day.

When we removed the numbers from `exceeds_gap?`, we also removed the
modulo operation. I had a feeling that would potentially cause problems,
and it turns out it did. Though it still took too much investigation
time to realise that the most obvious answer was in fact the correct
one. Blame the confusing test failures if I will:

    Failures:

      1) Chouette::VehicleJourney state_update should return errors when validation failed
         Failure/Error: expect(state['errors'][:vehicle_journey_at_stops].size).to eq 1

         NoMethodError:
           undefined method `[]' for nil:NilClass
         # ./spec/models/chouette/vehicle_journey_spec.rb:148:in `block (3 levels) in <top (required)>'

      2) Chouette::VehicleJourney state_update vehicle_journey_at_stops should return errors when validation failed
         Failure/Error: expect(item['errors'][:arrival_time].size).to eq 1

         NoMethodError:
           undefined method `[]' for nil:NilClass
         # ./spec/models/chouette/vehicle_journey_spec.rb:189:in `block (4 levels) in <top (required)>'

      3) VehicleJourneyImport.save should not import vehicle_journeys and not create objects when vehicle journey at stops are not in ascendant order
         Failure/Error: expect(VehicleJourneyImport.new(:route => route, :file => invalid_file_on_vjas_object).save).to be_falsey

           expected: falsey value
                got: true
         # ./spec/models/vehicle_journey_import_spec.rb:90:in `block (3 levels) in <top (required)>'

    Finished in 4 minutes 20.7 seconds (files took 14.47 seconds to load)
    1089 examples, 3 failures, 23 pending

    Failed examples:

    rspec ./spec/models/chouette/vehicle_journey_spec.rb:137 # Chouette::VehicleJourney state_update should return errors when validation failed
    rspec ./spec/models/chouette/vehicle_journey_spec.rb:183 # Chouette::VehicleJourney state_update vehicle_journey_at_stops should return errors when validation failed
    rspec ./spec/models/vehicle_journey_import_spec.rb:89 # VehicleJourneyImport.save should not import vehicle_journeys and not create objects when vehicle journey at stops are not in ascendant order

These three tests failed with my version of `exceeds_gap?`.

To correct the failures, add back in the 24-hour adjustment. Put it in a
named method that is hopefully clear enough to understand.

The second test failure ("vehicle_journey_at_stops should return errors
when validation failed") used two times that were the same. I decided to
add a test for this because it seemed like an interesting edge case. The
test I added didn't fail even for the previous version of
`.exceeds_gap?`, but I figure it seems like a useful test anyway.

Refs #870

2 files changed, 21 insertions, 1 deletions

diff --git a/lib/time_duration.rb b/lib/time_duration.rb
index f64c81bdd..12419fdc8 100644
--- a/lib/time_duration.rb
+++ b/lib/time_duration.rb
@@ -9,6 +9,12 @@ module TimeDuration
   #     Time.now + 2.hours
   #   )
   def self.exceeds_gap?(duration, earlier, later)
-    duration < (later - earlier)
+    duration < self.duration_without_24_hour_cycles(later - earlier)
+  end
+
+  private
+
+  def self.duration_without_24_hour_cycles(duration)
+    duration % 24.hours
   end
 end
diff --git a/spec/lib/time_duration_spec.rb b/spec/lib/time_duration_spec.rb
index 2d63eba76..1cba1f6d5 100644
--- a/spec/lib/time_duration_spec.rb
+++ b/spec/lib/time_duration_spec.rb
@@ -14,6 +14,20 @@ describe TimeDuration do
         t2 = Time.now + (4.hours + 1.minutes)
         expect(TimeDuration.exceeds_gap?(4.hours, t1, t2)).to be_truthy
       end
+
+      it "returns true when `earlier` is later than `later`" do
+        earlier = Time.new(2000, 1, 1, 11, 0, 0, 0)
+        later = Time.new(2000, 1, 1, 12, 0, 0, 0)
+
+        expect(TimeDuration.exceeds_gap?(4.hours, later, earlier)).to be true
+      end
+
+      it "returns false when `earlier` == `later`" do
+        earlier = Time.new(2000, 1, 1, 1, 0, 0, 0)
+        later = earlier
+
+        expect(TimeDuration.exceeds_gap?(4.hours, later, earlier)).to be false
+      end
     end
   end
 end