[x/simulation] RandSubsetCoins() should return sorted coinset (#5373)

Closes: #5372

x/simulation/rand_util.go

@@ -122,7 +122,7 @@ func RandSubsetCoins(r *rand.Rand, coins sdk.Coins) sdk.Coins {
 		}
 		subset = append(subset, sdk.NewCoin(c.Denom, amt))
 	}
-	return subset
+	return subset.Sort()
 }
 
 // DeriveRand derives a new Rand deterministically from another random source.

x/simulation/rand_util_test.go

@@ -0,0 +1,40 @@
+package simulation_test
+
+import (
+	"math/rand"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/x/simulation"
+)
+
+func TestRandSubsetCoins(t *testing.T) {
+	tests := []struct {
+		name  string
+		r     *rand.Rand
+		coins sdk.Coins
+	}{
+		{"seed=1", rand.New(rand.NewSource(1)), mustParseCoins("100stake,2testtoken")},
+		{"seed=50", rand.New(rand.NewSource(50)), mustParseCoins("100stake,2testtoken")},
+		{"seed=99", rand.New(rand.NewSource(99)), mustParseCoins("100stake,2testtoken")},
+	}
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			got := simulation.RandSubsetCoins(tt.r, tt.coins)
+			gotStringRep := got.String()
+			sortedStringRep := got.Sort().String()
+			require.Equal(t, gotStringRep, sortedStringRep)
+		})
+	}
+}
+
+func mustParseCoins(s string) sdk.Coins {
+	coins, err := sdk.ParseCoins(s)
+	if err != nil {
+		panic(err)
+	}
+	return coins
+}