address the first review comments

app/test_helpers.go

@@ -266,11 +266,8 @@ func IntegrationTestNetworkConfig() network.Config {
 	// execute ballot voting and thus clear out previous exchange rates, since we
 	// are not running a price-feeder.
 	oracleGenState.Params.VotePeriod = 1000
-	oracleGenState.ExchangeRates = append(oracleGenState.ExchangeRates, oracletypes.ExchangeRate{
-		Denom:     params.DisplayDenom,
-		Rate:      sdk.MustNewDecFromStr("34.21"),
-		Timestamp: time.Now(),
-	})
+	oracleGenState.ExchangeRates = append(oracleGenState.ExchangeRates, oracletypes.NewExchangeRate(
+		params.DisplayDenom, sdk.MustNewDecFromStr("34.21"), time.Now()))
 	// Set mock historic medians to satisfy leverage module's 24 median requirement
 	for i := 1; i <= 24; i++ {
 		median := oracletypes.Price{

x/oracle/abci.go

@@ -78,7 +78,7 @@ func CalcPrices(ctx sdk.Context, params types.Params, k keeper.Keeper) error {
 			return err
 		}
 		// save the exchange rate to store with denom and timestamp
-		k.SetExchangeRateWithEvent(ctx, denom, exchangeRate, ctx.BlockTime())
+		k.SetExchangeRateWithEvent(ctx, denom, exchangeRate)
 
 		if k.IsPeriodLastBlock(ctx, params.HistoricStampPeriod) {
 			k.AddHistoricPrice(ctx, denom, exchangeRate)

x/oracle/keeper/keeper.go

@@ -122,8 +122,8 @@ func (k Keeper) SetExchangeRate(ctx sdk.Context, denom string, rate sdk.Dec, t t
 
 // SetExchangeRateWithEvent sets an consensus
 // exchange rate to the store with ABCI event
-func (k Keeper) SetExchangeRateWithEvent(ctx sdk.Context, denom string, rate sdk.Dec, t time.Time) {
-	k.SetExchangeRate(ctx, denom, rate, t)
+func (k Keeper) SetExchangeRateWithEvent(ctx sdk.Context, denom string, rate sdk.Dec) {
+	k.SetExchangeRate(ctx, denom, rate, ctx.BlockTime())
 	sdkutil.Emit(&ctx, &types.EventSetFxRate{
 		Denom: denom, Rate: rate,
 	})

x/oracle/keeper/keeper_test.go

@@ -206,7 +206,7 @@ func (s *IntegrationTestSuite) TestAggregateExchangeRateVoteError() {
 
 func (s *IntegrationTestSuite) TestSetExchangeRateWithEvent() {
 	v := sdk.OneDec()
-	s.app.OracleKeeper.SetExchangeRateWithEvent(s.ctx, displayDenom, v, s.ctx.BlockTime())
+	s.app.OracleKeeper.SetExchangeRateWithEvent(s.ctx, displayDenom, v)
 	rate, err := s.app.OracleKeeper.GetExchangeRate(s.ctx, displayDenom)
 	s.Require().NoError(err)
 	s.Require().Equal(rate, types.ExchangeRate{Rate: v, Timestamp: s.ctx.BlockTime(), Denom: displayDenom})

x/oracle/types/exchange_rates.go

@@ -0,0 +1,16 @@
+package types
+
+import (
+	time "time"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+// NewExchangeRate creates a ExchangeRate instance
+func NewExchangeRate(denom string, exchangeRate sdk.Dec, t time.Time) ExchangeRate {
+	return ExchangeRate{
+		Denom:     denom,
+		Rate:      exchangeRate,
+		Timestamp: t,
+	}
+}