From 3f043b90ac83ab02e76f352cf83849f01b8db20b Mon Sep 17 00:00:00 2001
From: Nick DeLuca <nickdeluca08@gmail.com>
Date: Wed, 10 Jun 2020 09:18:13 -0500
Subject: [PATCH] Update GetTotalSurplus and GetTotalDebt to be consistent
 (#567)

* update GetTotalSurplus and GetTotalDebt code blocks to be consistent and
resolve feedback in exhibit 13

* spelling fix

* remove uneeded temp variables

* address PR feedback - use suite.Require() instead of default assertions
---
 x/cdp/keeper/auctions.go      |  8 ++---
 x/cdp/keeper/auctions_test.go | 60 +++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+), 6 deletions(-)

diff --git a/x/cdp/keeper/auctions.go b/x/cdp/keeper/auctions.go
index b6906865..c3ba3b35 100644
--- a/x/cdp/keeper/auctions.go
+++ b/x/cdp/keeper/auctions.go
@@ -88,18 +88,14 @@ func (k Keeper) NetSurplusAndDebt(ctx sdk.Context) error {
 // GetTotalSurplus returns the total amount of surplus tokens held by the liquidator module account
 func (k Keeper) GetTotalSurplus(ctx sdk.Context, accountName string) sdk.Int {
 	acc := k.supplyKeeper.GetModuleAccount(ctx, accountName)
-	totalSurplus := sdk.ZeroInt()
 	dp := k.GetParams(ctx).DebtParam
-	surplus := acc.GetCoins().AmountOf(dp.Denom)
-	totalSurplus = totalSurplus.Add(surplus)
-	return totalSurplus
+	return acc.GetCoins().AmountOf(dp.Denom)
 }
 
 // GetTotalDebt returns the total amount of debt tokens held by the liquidator module account
 func (k Keeper) GetTotalDebt(ctx sdk.Context, accountName string) sdk.Int {
 	acc := k.supplyKeeper.GetModuleAccount(ctx, accountName)
-	debt := acc.GetCoins().AmountOf(k.GetDebtDenom(ctx))
-	return debt
+	return acc.GetCoins().AmountOf(k.GetDebtDenom(ctx))
 }
 
 // RunSurplusAndDebtAuctions nets the surplus and debt balances and then creates surplus or debt auctions if the remaining balance is above the auction threshold parameter
diff --git a/x/cdp/keeper/auctions_test.go b/x/cdp/keeper/auctions_test.go
index 57273c7b..7f5edf14 100644
--- a/x/cdp/keeper/auctions_test.go
+++ b/x/cdp/keeper/auctions_test.go
@@ -92,6 +92,66 @@ func (suite *AuctionTestSuite) TestDebtAuction() {
 	suite.Equal(cs(c("debt", 90000000000)), acc.GetCoins())
 }
 
+func (suite *AuctionTestSuite) TestGetTotalSurplus() {
+	sk := suite.app.GetSupplyKeeper()
+
+	// liquidator account has zero coins
+	suite.Require().Equal(sdk.NewInt(0), suite.keeper.GetTotalSurplus(suite.ctx, types.LiquidatorMacc))
+
+	// mint some coins
+	err := sk.MintCoins(suite.ctx, types.LiquidatorMacc, cs(c("usdx", 100e6)))
+	suite.Require().NoError(err)
+	err = sk.MintCoins(suite.ctx, types.LiquidatorMacc, cs(c("usdx", 200e6)))
+	suite.Require().NoError(err)
+
+	// liquidator account has 300e6 total usdx
+	suite.Require().Equal(sdk.NewInt(300e6), suite.keeper.GetTotalSurplus(suite.ctx, types.LiquidatorMacc))
+
+	// mint some debt
+	err = sk.MintCoins(suite.ctx, types.LiquidatorMacc, cs(c("debt", 500e6)))
+	suite.Require().NoError(err)
+
+	// liquidator account still has 300e6 total usdx -- debt balance is ignored
+	suite.Require().Equal(sdk.NewInt(300e6), suite.keeper.GetTotalSurplus(suite.ctx, types.LiquidatorMacc))
+
+	// burn some usdx
+	err = sk.BurnCoins(suite.ctx, types.LiquidatorMacc, cs(c("usdx", 50e6)))
+	suite.Require().NoError(err)
+
+	// liquidator usdx decreases
+	suite.Require().Equal(sdk.NewInt(250e6), suite.keeper.GetTotalSurplus(suite.ctx, types.LiquidatorMacc))
+}
+
+func (suite *AuctionTestSuite) TestGetTotalDebt() {
+	sk := suite.app.GetSupplyKeeper()
+
+	// liquidator account has zero debt
+	suite.Require().Equal(sdk.NewInt(0), suite.keeper.GetTotalSurplus(suite.ctx, types.LiquidatorMacc))
+
+	// mint some debt
+	err := sk.MintCoins(suite.ctx, types.LiquidatorMacc, cs(c("debt", 100e6)))
+	suite.Require().NoError(err)
+	err = sk.MintCoins(suite.ctx, types.LiquidatorMacc, cs(c("debt", 200e6)))
+	suite.Require().NoError(err)
+
+	// liquidator account has 300e6 total debt
+	suite.Require().Equal(sdk.NewInt(300e6), suite.keeper.GetTotalDebt(suite.ctx, types.LiquidatorMacc))
+
+	// mint some usdx
+	err = sk.MintCoins(suite.ctx, types.LiquidatorMacc, cs(c("usdx", 500e6)))
+	suite.Require().NoError(err)
+
+	// liquidator account still has 300e6 total debt -- usdx balance is ignored
+	suite.Require().Equal(sdk.NewInt(300e6), suite.keeper.GetTotalDebt(suite.ctx, types.LiquidatorMacc))
+
+	// burn some debt
+	err = sk.BurnCoins(suite.ctx, types.LiquidatorMacc, cs(c("debt", 50e6)))
+	suite.Require().NoError(err)
+
+	// liquidator debt decreases
+	suite.Require().Equal(sdk.NewInt(250e6), suite.keeper.GetTotalDebt(suite.ctx, types.LiquidatorMacc))
+}
+
 func TestAuctionTestSuite(t *testing.T) {
 	suite.Run(t, new(AuctionTestSuite))
 }