Run test at a fixed time

Due to how HLLRedisCounter#weekly_redis_keys converts
dates to calendar week, it would result in an empty
array when the calendar week of end_date occurs before
the calendar week of start_date.

For example, given start_date 2020-12-01 and
end_date 2021-01-01, the calendar week would be reversed,
resulting in empty array from #weekly_redis_keys

spec/services/ci/build_report_result_service_spec.rb

@@ -6,6 +6,12 @@ RSpec.describe Ci::BuildReportResultService do
   describe '#execute', :clean_gitlab_redis_shared_state do
     subject(:build_report_result) { described_class.new.execute(build) }
 
+    around do |example|
+      travel_to(DateTime.parse('2020-07-01')) do
+        example.run
+      end
+    end
+
     context 'when build is finished' do
       let(:build) { create(:ci_build, :success, :test_reports) }