add specs for preventing nil zones in util presenters

refs CNVS-16799

No behavior change, just proving that when you
explicitly pass in a nil object to a date or time
presenter as a zone override, it uses the default
Time.zone correctly. the actual behavioaral change
went out in a hotfix in /c/44148

TEST PLAN: specs should pass

Change-Id: I59da9cf68d5738b1006ae1579db2946731468539
Reviewed-on: https://gerrit.instructure.com/44159
Reviewed-by: Simon Williams <simon@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Simon Williams <simon@instructure.com>
Product-Review: Ethan Vizitei <evizitei@instructure.com>

lib/utils/datetime_range_presenter.rb

@@ -44,11 +44,13 @@ module Utils
 
     def present_range
       if start.to_date == finish.to_date
-        I18n.t('time.ranges.same_day', "%{date} from %{start_time} to %{end_time}", date: start_date_string, start_time: start_as_time, end_time: finish_as_time)
+        I18n.t('time.ranges.same_day', "%{date} from %{start_time} to %{end_time}",
+               date: start_date_string, start_time: start_as_time, end_time: finish_as_time)
       else
         start_string = datetime_component(start_date_string, start)
         end_string = datetime_component(end_date_string, finish)
-        I18n.t('time.ranges.different_days', "%{start_date_and_time} to %{end_date_and_time}", start_date_and_time: start_string, end_date_and_time: end_string)
+        I18n.t('time.ranges.different_days', "%{start_date_and_time} to %{end_date_and_time}",
+               start_date_and_time: start_string, end_date_and_time: end_string)
       end
     end
 

spec/lib/utils/datetime_range_presenter_spec.rb

@@ -19,6 +19,11 @@ require_relative '../../spec_helper'
 
 module Utils
   describe DatetimeRangePresenter do
+    def overridden_presenter(datetime, zone_name)
+      zone = ActiveSupport::TimeZone[zone_name]
+      DatetimeRangePresenter.new(datetime, nil, :event, zone)
+    end
+
     describe "#as_string" do
       it 'can display a single datetime if theres no range' do
         datetime = Time.zone.parse("#{Time.zone.now.year}-01-01 12:00:00")
@@ -74,12 +79,21 @@ module Utils
 
       it "accepts a timezone override" do
         datetime = Time.zone.parse("#{Time.zone.now.year}-01-01 12:00:00")
-        mountain_presenter = DatetimeRangePresenter.new(datetime, nil, :event, ActiveSupport::TimeZone["America/Denver"])
-        central_presenter = DatetimeRangePresenter.new(datetime, nil, :event, ActiveSupport::TimeZone["America/Chicago"])
+        mountain_presenter = overridden_presenter(datetime, "America/Denver")
+        central_presenter = overridden_presenter(datetime, "America/Chicago")
         expect(mountain_presenter.as_string).to eq("Jan 1 at  5am")
         expect(central_presenter.as_string).to eq("Jan 1 at  6am")
       end
 
+      it "uses the default timezone if none provided" do
+        datetime = Time.zone.parse("#{Time.zone.now.year}-01-01 12:00:00")
+        pre_zone = Time.zone
+        Time.zone = "Mountain Time (US & Canada)"
+        nilzone_presenter = DatetimeRangePresenter.new(datetime, nil, :event, nil)
+        expect(nilzone_presenter.as_string).to eq("Jan 1 at  5am")
+        Time.zone = pre_zone
+      end
+
       it "can deal with date boundaries in the override on time objects" do
         pre_zone = Time.zone
         Time.zone = "Alaska"
@@ -87,7 +101,7 @@ module Utils
         datetime = Time.now
 
         alaskan_presenter = DatetimeRangePresenter.new(datetime)
-        mountain_presenter = DatetimeRangePresenter.new(datetime, nil, :event,  ActiveSupport::TimeZone["America/Denver"])
+        mountain_presenter = overridden_presenter(datetime, "America/Denver")
         expect(alaskan_presenter.as_string).to eq("Sep 30 at 11:30pm")
         expect(mountain_presenter.as_string).to eq("Oct 1 at  1:30am")
         Timecop.return

spec/lib/utils/time_presenter_spec.rb

@@ -61,6 +61,12 @@ module Utils
         presenter = TimePresenter.new(time, zone)
         expect(presenter.as_string).to_not eq(native_zone_presenter.as_string)
       end
+
+      it 'can handle a nil zone override' do
+        native_zone_presenter = TimePresenter.new(time, nil)
+        explicit_presenter = TimePresenter.new(time, Time.zone)
+        expect(explicit_presenter.as_string).to eq(native_zone_presenter.as_string)
+      end
     end
   end
 end