feat(Governance): Add additional node provider rewards check to upgrade_canisters_with_golden_nns_state test (#8433)

This pull request adds an additional check for Node Provider rewards.
The new assertion ensures that rewards are distributed over contiguous
periods, preventing any gaps in days between subsequent reward
distributions.

Author: pietrodimarco-dfinity

rs/nns/integration_tests/src/upgrade_canisters_with_golden_nns_state.rs

@@ -404,6 +404,7 @@ mod sanity_check {
     use super::*;
     use ic_nervous_system_common::ONE_MONTH_SECONDS;
     use ic_nns_governance::governance::NODE_PROVIDER_REWARD_PERIOD_SECONDS;
+    use ic_nns_governance_api::DateUtc;
 
     /// Metrics fetched from canisters either before or after testing.
     pub struct Metrics {
@@ -442,10 +443,11 @@ mod sanity_check {
     fn advance_time(state_machine: &StateMachine, before_timestamp: u64) {
         // Advance time in the state machine to just before the next node provider
         // rewards distribution time.
+        let seconds_to_node_provider_reward_distribution = before_timestamp
+            + NODE_PROVIDER_REWARD_PERIOD_SECONDS
+            - state_machine.get_time().as_secs_since_unix_epoch();
         state_machine.advance_time(std::time::Duration::from_secs(
-            before_timestamp + NODE_PROVIDER_REWARD_PERIOD_SECONDS
-                - state_machine.get_time().as_secs_since_unix_epoch()
-                - 1,
+            seconds_to_node_provider_reward_distribution - 1,
         ));
         for _ in 0..100 {
             state_machine.advance_time(std::time::Duration::from_secs(1));
@@ -454,7 +456,9 @@ mod sanity_check {
 
         // Advance time in the state machine by one month to ensure that voting rewards
         // are also distributed.
-        state_machine.advance_time(std::time::Duration::from_secs(ONE_MONTH_SECONDS));
+        state_machine.advance_time(std::time::Duration::from_secs(
+            ONE_MONTH_SECONDS - seconds_to_node_provider_reward_distribution,
+        ));
         for _ in 0..100 {
             state_machine.advance_time(std::time::Duration::from_secs(1));
             state_machine.tick();
@@ -546,6 +550,25 @@ mod sanity_check {
                     assert_increased(before, after, "node provider rewards timestamp");
                 },
             );
+
+            // Check node provider rewards cover contiguous periods.
+            let before_end_date = self
+                .before
+                .governance_most_recent_monthly_node_provider_rewards
+                .end_date
+                .clone()
+                .unwrap();
+            let expected_after_start_date = DateUtc {
+                year: before_end_date.year,
+                month: before_end_date.month,
+                day: before_end_date.day + 1,
+            };
+            assert_eq!(
+                self.after
+                    .governance_most_recent_monthly_node_provider_rewards
+                    .start_date,
+                Some(expected_after_start_date)
+            );
         }
 
         fn check_metric<T>(&self, transform: impl Fn(&Metrics) -> T, assertion: impl Fn(T, T)) {