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tests: inflation rate change (#2236)
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* tests: inflation tests

* add inflation change test

* finish tests
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@robert-zaremba
robert-zaremba authored Sep 12, 2023
1 parent e42a6ef commit a45fc53
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Showing 3 changed files with 108 additions and 54 deletions.
10 changes: 8 additions & 2 deletions app/inflation/inflation.go
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Original file line number Diff line number Diff line change
Expand Up @@ -34,8 +34,7 @@ func (c Calculator) InflationRate(ctx sdk.Context, minter minttypes.Minter, mint
factor := bpmath.One - inflationParams.InflationReductionRate
mintParams.InflationMax = factor.MulDec(mintParams.InflationMax)
mintParams.InflationMin = factor.MulDec(mintParams.InflationMin)
// inflation rate change = (max rate - min rate) / 6months
mintParams.InflationRateChange = sdk.NewDec(2).Mul(mintParams.InflationMax.Sub(mintParams.InflationMin))
mintParams.InflationRateChange = fastInflationRateChange(mintParams)
c.MintKeeper.SetParams(ctx, mintParams)

err := ugovKeeper.SetInflationCycleEnd(ctx.BlockTime().Add(inflationParams.InflationCycle))
Expand All @@ -50,6 +49,13 @@ func (c Calculator) InflationRate(ctx sdk.Context, minter minttypes.Minter, mint
return c.AdjustInflation(stakingTokenSupply, inflationParams.MaxSupply.Amount, minter, mintParams)
}

var two = sdk.NewDec(2)

// inflation rate change = (max_rate - min_rate) * 2
func fastInflationRateChange(p minttypes.Params) sdk.Dec {
return two.Mul(p.InflationMax.Sub(p.InflationMin))
}

// AdjustInflation checks if newly minting coins will execeed the MaxSupply then it will adjust the inflation with
// respect to MaxSupply
func (c Calculator) AdjustInflation(stakingTokenSupply, maxSupply math.Int, minter minttypes.Minter,
Expand Down
145 changes: 93 additions & 52 deletions app/inflation/inflation_test.go
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
package inflation_test
package inflation

import (
"testing"
Expand All @@ -11,11 +11,11 @@ import (
"github.com/golang/mock/gomock"
"gotest.tools/v3/assert"

"github.com/umee-network/umee/v6/app/inflation"
mocks "github.com/umee-network/umee/v6/app/inflation/mocks"
appparams "github.com/umee-network/umee/v6/app/params"
"github.com/umee-network/umee/v6/tests/tsdk"
"github.com/umee-network/umee/v6/util/bpmath"
"github.com/umee-network/umee/v6/util/checkers"
"github.com/umee-network/umee/v6/util/coin"
"github.com/umee-network/umee/v6/x/ugov"
ugovmocks "github.com/umee-network/umee/v6/x/ugov/mocks"
Expand Down Expand Up @@ -66,7 +66,7 @@ func TestAdjustInflation(t *testing.T) {

for _, test := range tests {
t.Run(test.name, func(t *testing.T) {
calc := inflation.Calculator{}
calc := Calculator{}
mintParams := test.params(mintParams)
result := calc.AdjustInflation(test.totalSupply, test.maxSupply, test.minter, mintParams)

Expand Down Expand Up @@ -216,7 +216,7 @@ func TestInflationRate(t *testing.T) {
mockUGovKeeper.EXPECT().InflationCycleEnd().Return(test.cycleEndTime()).AnyTimes()
mockUGovKeeper.EXPECT().SetInflationCycleEnd(gomock.Any()).Return(nil).AnyTimes()

calc := inflation.Calculator{
calc := Calculator{
MintKeeper: mockMintKeeper,
UgovKeeperB: ugovmocks.NewParamsBuilder(mockUGovKeeper),
}
Expand All @@ -229,65 +229,106 @@ func TestInflationRate(t *testing.T) {
}
}

func TestNextInflationRate(t *testing.T) {
minter := minttypes.Minter{
Inflation: sdk.NewDecWithPrec(0, 2),
func TestInflationRateChange(t *testing.T) {
bondedRatio := sdk.NewDecWithPrec(1, 1) // 10% -> below the goal
mparamsStd := minttypes.Params{ // minting params for a standard x/mint minting process
MintDenom: sdk.DefaultBondDenom,
InflationMax: sdk.NewDecWithPrec(5, 1), // 0.5
InflationMin: sdk.NewDecWithPrec(1, 1), // 0.1
GoalBonded: sdk.NewDecWithPrec(5, 1), // 0.5
BlocksPerYear: 5 * 60 * 24 * 365, // 1 block per 6s => 5 blocks per min.
}
mparamsFast := mparamsStd // minting params for the umee inflation calculator
mparamsFast.InflationRateChange = fastInflationRateChange(mparamsFast)
mparamsStd.InflationRateChange = mparamsFast.InflationRateChange.Quo(two)
minterFast := minttypes.Minter{
Inflation: sdk.NewDecWithPrec(1, 2), // 0.01 -- less than InflationMin
}
minterStd := minterFast

mintParams := minttypes.DefaultParams()
mintParams.InflationMax = sdk.NewDecWithPrec(40, 2)
mintParams.InflationMin = sdk.NewDecWithPrec(1, 2)
mintParams.InflationRateChange = sdk.NewDec(1)
mintParams.BlocksPerYear = 100
mintParams.GoalBonded = sdk.NewDec(33)
//
// Test1: inflation rate should jump to InflationMin in the first round.
//
ir := minterFast.NextInflationRate(mparamsFast, bondedRatio)
assert.Equal(t, ir, mparamsFast.InflationMin, "initial rate should immediately adjust to InflationMin")

bondedRatio := sdk.NewDec(20)
//
// Test2
// in half a year inflation should go from 0 towards max. Note: with the existing Cosmos SDK
// algorithm, we won't reach max. So we compare our settings with the standard minter, and check
// if it's almost the same.
//

// default inflation rate (1 year inflation rate change speed )
ir := minter.NextInflationRate(mintParams, bondedRatio)
assert.DeepEqual(t, mintParams.InflationMin, ir)
// in 5 months, the fast minter should not reach the max.
month := int(mparamsFast.BlocksPerYear / 12)
for i := 0; i <= month*5; i++ {
minterFast.Inflation = minterFast.NextInflationRate(mparamsFast, bondedRatio)
}
assert.Assert(t, minterFast.Inflation.LT(mparamsFast.InflationMax), "current: %v", minterFast.Inflation)

// changing inflation rate speed from 1 year to 6 months
mintParams.BlocksPerYear = mintParams.BlocksPerYear * 2
nir := minter.NextInflationRate(mintParams, bondedRatio)
// we should get similar result to the standard minter after 10 months
for i := 0; i <= month*10; i++ {
minterStd.Inflation = minterStd.NextInflationRate(mparamsStd, bondedRatio)
}

assert.DeepEqual(t, mintParams.InflationMin, nir)
}
checkers.RequireDecMaxDiff(t, minterStd.Inflation, minterFast.Inflation, sdk.NewDecWithPrec(1, 5),
"fast minter and standard minter should end up with similar inflation change after 5months and 10months repectively")

func TestInflationRateChange(t *testing.T) {
minter := minttypes.Minter{
Inflation: sdk.NewDecWithPrec(0, 2),
// continue one more month
for i := 0; i <= month; i++ {
minterFast.Inflation = minterFast.NextInflationRate(mparamsFast, bondedRatio)
}
checkers.RequireDecMaxDiff(t, mparamsFast.InflationMax, minterFast.Inflation,
mparamsFast.InflationRateChange.QuoInt64(10),
"fast minter, afer 6 months should go close enough to max")

mintParams := minttypes.DefaultParams()
mintParams.InflationMax = sdk.NewDecWithPrec(5, 1) // 0.5
mintParams.InflationMin = sdk.NewDecWithPrec(2, 2) // 0.02
mintParams.InflationRateChange = sdk.NewDec(1) // will be overwritten in the `NextInflationRate`
mintParams.BlocksPerYear = 100
//
// test3, let's see with smaller min and max.
//
mparamsFast.InflationMin = sdk.NewDecWithPrec(3, 2) // 0.03
mparamsFast.InflationMax = sdk.NewDecWithPrec(7, 2) // 0.07
minterFast.Inflation = sdk.NewDecWithPrec(1, 2) // 0.01
for i := 0; i <= month*6; i++ {
minterFast.Inflation = minterFast.NextInflationRate(mparamsFast, bondedRatio)
}
checkers.RequireDecMaxDiff(t, mparamsFast.InflationMax, minterFast.Inflation,
mparamsFast.InflationRateChange.QuoInt64(10),
"fast minter, afer 6 months should go close enough to max")

//
// test 4 check going from max towards min
//
bondedRatio = sdk.NewDecWithPrec(9, 1) // 0.7
minterFast.Inflation = sdk.NewDecWithPrec(9, 1) // 0.9
mparamsFast.InflationRateChange = fastInflationRateChange(mparamsFast)

ir = minterFast.NextInflationRate(mparamsFast, bondedRatio)
assert.Equal(t, ir, mparamsFast.InflationMax, "initial rate should immediately adjust to InflationMin")

// in 5 months, the fast minter should not reach the min.
for i := 0; i <= month*5; i++ {
minterFast.Inflation = minterFast.NextInflationRate(mparamsFast, bondedRatio)
}
assert.Assert(t, minterFast.Inflation.GT(mparamsFast.InflationMin), "current: %v", minterFast.Inflation)

bondedRatio := sdk.NewDecWithPrec(1, 2)
// after 50 blocks (half the year) inflation will be updated
// every block, inflation = prevInflation + currentInflationRateChange
var ir sdk.Dec
ir = minter.NextInflationRate(mintParams, bondedRatio)
// at initial based on bondedRatio and GoalBonded , the inflation will be at mintParams.InflationMin
assert.Equal(t, ir, mintParams.InflationMin)
for i := 0; i < 50; i++ {
ir = minter.NextInflationRate(mintParams, bondedRatio)
minter.Inflation = ir
// continue one more month
for i := 0; i <= month; i++ {
minterFast.Inflation = minterFast.NextInflationRate(mparamsFast, bondedRatio)
}
// current inflation after the 50 blocks will be increased to MaxInflationRate
nir := minter.NextInflationRate(mintParams, bondedRatio)
assert.Equal(t, nir, mintParams.InflationMax)
checkers.RequireDecMaxDiff(t, mparamsFast.InflationMin, minterFast.Inflation,
mparamsFast.InflationRateChange.QuoInt64(10),
"fast minter, afer 6 months should go close enough to min")

// current bonded ratio =1 then inflation rate change per year will be negative
// so after the 50 blocks inflation will be minimum
minter.Inflation = sdk.NewDecWithPrec(2, 2)
bondedRatio = sdk.NewDec(1)
for i := 0; i < 50; i++ {
ir = minter.NextInflationRate(mintParams, bondedRatio)
minter.Inflation = ir
//
// test 5, when bondedRatio is closer to the goal bonded we should still go fast.
//
bondedRatio = sdk.NewDecWithPrec(7, 1) // 0.7
minterFast.Inflation = sdk.NewDecWithPrec(9, 1) // 0.9
// continue one more month
for i := 0; i <= month*6; i++ {
minterFast.Inflation = minterFast.NextInflationRate(mparamsFast, bondedRatio)
}
// it should be minimum , because inflationRateChangePerYear will be negative
assert.Equal(t, ir, mintParams.InflationMin)
checkers.RequireDecMaxDiff(t, mparamsFast.InflationMin, minterFast.Inflation,
mparamsFast.InflationRateChange.QuoInt64(3), // TODO: the diff should be smaller, but it will require to change the standard cosmos infation rate algorithm
"fast minter, afer 6 months should go close enough to min")
}
7 changes: 7 additions & 0 deletions util/checkers/number.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,8 +2,10 @@ package checkers

import (
"fmt"
"testing"

sdk "github.com/cosmos/cosmos-sdk/types"
"github.com/stretchr/testify/require"
"golang.org/x/exp/constraints"
)

Expand Down Expand Up @@ -33,6 +35,11 @@ func DecMaxDiff(a, b, maxDiff sdk.Dec, note string) error {
return nil
}

func RequireDecMaxDiff(t *testing.T, a, b, maxDiff sdk.Dec, note string) {
err := DecMaxDiff(a, b, maxDiff, note)
require.NoError(t, err)
}

// DecInZeroOne asserts that 0 <= a <= 1 when oneInclusive=True, otherwise asserts
// 0 <= a < 1
func DecInZeroOne(a sdk.Dec, name string, oneInclusive bool) error {
Expand Down

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