test: add tests for HistoricalRewards

x/farming/keeper/reward.go

@@ -10,10 +10,14 @@ import (
 	"github.com/tendermint/farming/x/farming/types"
 )
 
-func (k Keeper) GetHistoricalRewards(ctx sdk.Context, stakingCoinDenom string, epoch uint64) (rewards types.HistoricalRewards) {
+func (k Keeper) GetHistoricalRewards(ctx sdk.Context, stakingCoinDenom string, epoch uint64) (rewards types.HistoricalRewards, found bool) {
 	store := ctx.KVStore(k.storeKey)
 	bz := store.Get(types.GetHistoricalRewardsKey(stakingCoinDenom, epoch))
+	if bz == nil {
+		return
+	}
 	k.cdc.MustUnmarshal(bz, &rewards)
+	found = true
 	return
 }
 
@@ -132,8 +136,8 @@ func (k Keeper) CalculateRewards(ctx sdk.Context, farmerAcc sdk.AccAddress, stak
 		return sdk.NewDecCoins()
 	}
 
-	starting := k.GetHistoricalRewards(ctx, stakingCoinDenom, staking.StartingEpoch-1)
-	ending := k.GetHistoricalRewards(ctx, stakingCoinDenom, endingEpoch)
+	starting, _ := k.GetHistoricalRewards(ctx, stakingCoinDenom, staking.StartingEpoch-1)
+	ending, _ := k.GetHistoricalRewards(ctx, stakingCoinDenom, endingEpoch)
 	diff := ending.CumulativeUnitRewards.Sub(starting.CumulativeUnitRewards)
 	rewards = diff.MulDecTruncate(staking.Amount.ToDec())
 	return
@@ -335,7 +339,7 @@ func (k Keeper) AllocateRewards(ctx sdk.Context) error {
 
 	for stakingCoinDenom, unitRewards := range unitRewardsByDenom {
 		currentEpoch := k.GetCurrentEpoch(ctx, stakingCoinDenom)
-		historical := k.GetHistoricalRewards(ctx, stakingCoinDenom, currentEpoch-1)
+		historical, _ := k.GetHistoricalRewards(ctx, stakingCoinDenom, currentEpoch-1)
 		k.SetHistoricalRewards(ctx, stakingCoinDenom, currentEpoch, types.HistoricalRewards{
 			CumulativeUnitRewards: historical.CumulativeUnitRewards.Add(unitRewards...),
 		})

x/farming/keeper/reward_test.go

@@ -310,3 +310,46 @@ func (suite *KeeperTestSuite) TestHarvest() {
 func (suite *KeeperTestSuite) TestMultipleHarvest() {
 	// TODO: implement
 }
+
+func (suite *KeeperTestSuite) TestHistoricalRewards() {
+	suite.ctx = suite.ctx.WithBlockTime(types.ParseTime("2021-08-06T00:00:00Z"))
+
+	// Create two plans that share same staking coin denom in their staking coin weights.
+	suite.SetFixedAmountPlan(1, suite.addrs[4], map[string]string{denom1: "1"}, map[string]int64{denom3: 1000000})
+	suite.SetFixedAmountPlan(2, suite.addrs[4], map[string]string{denom1: "1"}, map[string]int64{denom3: 1000000})
+
+	// Advancing epoch(s) before any staking is made doesn't create any historical rewards records.
+	suite.AdvanceEpoch()
+	suite.AdvanceEpoch()
+	count := 0
+	suite.keeper.IterateHistoricalRewards(suite.ctx, func(stakingCoinDenom string, epoch uint64, rewards types.HistoricalRewards) (stop bool) {
+		count++
+		return false
+	})
+	suite.Equal(count, 0)
+
+	suite.Stake(suite.addrs[0], sdk.NewCoins(sdk.NewInt64Coin(denom1, 1000000)))
+	// Advancing epoch here marks queued staking coins as staked.
+	suite.AdvanceEpoch()
+
+	// After a farmer has staked(not queued) coins, historical rewards records will be created for each epoch.
+	// Here we advance epoch three times, and this will create 3 historical rewards records.
+	suite.AdvanceEpoch()
+	suite.AdvanceEpoch()
+	suite.AdvanceEpoch()
+
+	// First, ensure that we have only 3 entries in the store.
+	count = 0
+	suite.keeper.IterateHistoricalRewards(suite.ctx, func(stakingCoinDenom string, epoch uint64, rewards types.HistoricalRewards) (stop bool) {
+		count++
+		return false
+	})
+	suite.Require().Equal(count, 3)
+
+	// Next, check if cumulative unit rewards is correct.
+	for i := uint64(0); i < 3; i++ {
+		historical, found := suite.keeper.GetHistoricalRewards(suite.ctx, denom1, i)
+		suite.Require().True(found)
+		suite.Require().True(decCoinsEq(sdk.NewDecCoins(sdk.NewInt64DecCoin(denom3, int64((i+1)*2))), historical.CumulativeUnitRewards))
+	}
+}