add test for CalcExitPool (#1540)

* add test for CalcExitPool

* minor

* some change in lp_test

* Update x/gamm/pool-models/internal/cfmm_common/lp_test.go

Co-authored-by: Roman <roman@osmosis.team>

* update lp_test.go

Co-authored-by: vuong <56973102+vuong177@users.noreply.github.com>
Co-authored-by: Roman <roman@osmosis.team>

x/gamm/pool-models/internal/cfmm_common/lp.go

@@ -10,13 +10,13 @@ import (
 	"github.com/osmosis-labs/osmosis/v7/x/gamm/types"
 )
 
-const errMsgFormatSharesLargerThanMax = "%d resulted shares is larger than the max amount of %d"
+const errMsgFormatSharesLargerThanMax = "%s resulted shares is larger than the max amount of %s"
 
 // CalcExitPool returns how many tokens should come out, when exiting k LP shares against a "standard" CFMM
 func CalcExitPool(ctx sdk.Context, pool types.PoolI, exitingShares sdk.Int, exitFee sdk.Dec) (sdk.Coins, error) {
 	totalShares := pool.GetTotalShares()
 	if exitingShares.GTE(totalShares) {
-		return sdk.Coins{}, sdkerrors.Wrapf(types.ErrLimitMaxAmount, errMsgFormatSharesLargerThanMax, exitingShares.Int64(), totalShares.Uint64())
+		return sdk.Coins{}, sdkerrors.Wrapf(types.ErrLimitMaxAmount, errMsgFormatSharesLargerThanMax, exitingShares, totalShares)
 	}
 
 	// refundedShares = exitingShares * (1 - exit fee)

x/gamm/pool-models/internal/cfmm_common/lp_test.go

@@ -0,0 +1,139 @@
+package cfmm_common_test
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/osmosis-labs/osmosis/v7/x/gamm/pool-models/balancer"
+	"github.com/osmosis-labs/osmosis/v7/x/gamm/pool-models/internal/cfmm_common"
+	"github.com/osmosis-labs/osmosis/v7/x/gamm/pool-models/stableswap"
+	gammtypes "github.com/osmosis-labs/osmosis/v7/x/gamm/types"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+// a helper function used to multiply coins
+func mulCoins(coins sdk.Coins, multiplier sdk.Dec) sdk.Coins {
+	outCoins := sdk.Coins{}
+	for _, coin := range coins {
+		outCoin := sdk.NewCoin(coin.Denom, multiplier.MulInt(coin.Amount).TruncateInt())
+		if !outCoin.Amount.IsZero() {
+			outCoins = append(outCoins, outCoin)
+		}
+	}
+	return outCoins
+}
+
+func TestCalcExitPool(t *testing.T) {
+
+	emptyContext := sdk.Context{}
+
+	twoStablePoolAssets := sdk.NewCoins(
+		sdk.NewInt64Coin("foo", 1000000000),
+		sdk.NewInt64Coin("bar", 1000000000),
+	)
+
+	threeBalancerPoolAssets := []balancer.PoolAsset{
+		{Token: sdk.NewInt64Coin("foo", 2000000000), Weight: sdk.NewIntFromUint64(5)},
+		{Token: sdk.NewInt64Coin("bar", 3000000000), Weight: sdk.NewIntFromUint64(5)},
+		{Token: sdk.NewInt64Coin("baz", 4000000000), Weight: sdk.NewIntFromUint64(5)},
+	}
+
+	// create these pools used for testing
+	twoAssetPool, err := stableswap.NewStableswapPool(
+		1,
+		stableswap.PoolParams{ExitFee: sdk.ZeroDec()},
+		twoStablePoolAssets,
+		"",
+		time.Now(),
+	)
+	require.NoError(t, err)
+
+	threeAssetPool, err := balancer.NewBalancerPool(
+		1,
+		balancer.PoolParams{SwapFee: sdk.ZeroDec(), ExitFee: sdk.ZeroDec()},
+		threeBalancerPoolAssets,
+		"",
+		time.Now(),
+	)
+	require.NoError(t, err)
+
+	twoAssetPoolWithExitFee, err := stableswap.NewStableswapPool(
+		1,
+		stableswap.PoolParams{ExitFee: sdk.MustNewDecFromStr("0.0001")},
+		twoStablePoolAssets,
+		"",
+		time.Now(),
+	)
+	require.NoError(t, err)
+
+	threeAssetPoolWithExitFee, err := balancer.NewBalancerPool(
+		1,
+		balancer.PoolParams{SwapFee: sdk.ZeroDec(), ExitFee: sdk.MustNewDecFromStr("0.0002")},
+		threeBalancerPoolAssets,
+		"",
+		time.Now(),
+	)
+	require.NoError(t, err)
+
+	tests := []struct {
+		name          string
+		pool          gammtypes.PoolI
+		exitingShares sdk.Int
+		expError      bool
+	}{
+		{
+			name:          "two-asset pool, exiting shares grater than total shares",
+			pool:          &twoAssetPool,
+			exitingShares: twoAssetPool.GetTotalShares().AddRaw(1),
+			expError:      true,
+		},
+		{
+			name:          "three-asset pool, exiting shares grater than total shares",
+			pool:          &threeAssetPool,
+			exitingShares: threeAssetPool.GetTotalShares().AddRaw(1),
+			expError:      true,
+		},
+		{
+			name:          "two-asset pool, valid exiting shares",
+			pool:          &twoAssetPool,
+			exitingShares: twoAssetPool.GetTotalShares().QuoRaw(2),
+			expError:      false,
+		},
+		{
+			name:          "three-asset pool, valid exiting shares",
+			pool:          &threeAssetPool,
+			exitingShares: sdk.NewIntFromUint64(3000000000000),
+			expError:      false,
+		},
+		{
+			name:          "two-asset pool with exit fee, valid exiting shares",
+			pool:          &twoAssetPoolWithExitFee,
+			exitingShares: twoAssetPoolWithExitFee.GetTotalShares().QuoRaw(2),
+			expError:      false,
+		},
+		{
+			name:          "three-asset pool with exit fee, valid exiting shares",
+			pool:          &threeAssetPoolWithExitFee,
+			exitingShares: sdk.NewIntFromUint64(7000000000000),
+			expError:      false,
+		},
+	}
+
+	for _, test := range tests {
+		// using empty context since, currently, the context is not used anyway. This might be changed in the future
+		exitFee := test.pool.GetExitFee(emptyContext)
+		exitCoins, err := cfmm_common.CalcExitPool(emptyContext, test.pool, test.exitingShares, exitFee)
+		if test.expError {
+			require.Error(t, err, "test: %v", test.name)
+		} else {
+			require.NoError(t, err, "test: %v", test.name)
+
+			// exitCoins = ( (1 - exitFee) * exitingShares / poolTotalShares ) * poolTotalLiquidity
+			expExitCoins := mulCoins(test.pool.GetTotalPoolLiquidity(emptyContext), (sdk.OneDec().Sub(exitFee)).MulInt(test.exitingShares).QuoInt(test.pool.GetTotalShares()))
+			require.Equal(t, expExitCoins.Sort().String(), exitCoins.Sort().String(), "test: %v", test.name)
+		}
+	}
+}