diff --git a/x/simulation/account_test.go b/x/simulation/account_test.go
new file mode 100644
index 000000000..adb28dcf9
--- /dev/null
+++ b/x/simulation/account_test.go
@@ -0,0 +1,77 @@
+package simulation_test
+
+import (
+	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/x/simulation"
+)
+
+func TestRandomAccounts(t *testing.T) {
+	t.Parallel()
+	r := rand.New(rand.NewSource(time.Now().Unix()))
+	tests := []struct {
+		name string
+		n    int
+		want int
+	}{
+		{"0-accounts", 0, 0},
+		{"0-accounts", 1, 1},
+		{"0-accounts", 1_000, 1_000},
+	}
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			got := simulation.RandomAccounts(r, tt.n)
+			require.Equal(t, tt.want, len(got))
+			if tt.n == 0 {
+				return
+			}
+			acc, i := simulation.RandomAcc(r, got)
+			require.True(t, acc.Equals(got[i]))
+			accFound, found := simulation.FindAccount(got, acc.Address)
+			require.True(t, found)
+			require.True(t, accFound.Equals(acc))
+		})
+	}
+}
+
+func TestFindAccountEmptySlice(t *testing.T) {
+	t.Parallel()
+	r := rand.New(rand.NewSource(time.Now().Unix()))
+	accs := simulation.RandomAccounts(r, 1)
+	require.Equal(t, 1, len(accs))
+	acc, found := simulation.FindAccount(nil, accs[0].Address)
+	require.False(t, found)
+	require.Nil(t, acc.Address)
+	require.Nil(t, acc.PrivKey)
+	require.Nil(t, acc.PubKey)
+}
+
+func TestRandomFees(t *testing.T) {
+	t.Parallel()
+	r := rand.New(rand.NewSource(time.Now().Unix()))
+	tests := []struct {
+		name           string
+		spendableCoins sdk.Coins
+		wantEmpty      bool
+		wantErr        bool
+	}{
+		{"0 coins", sdk.Coins{}, true, false},
+		{"0 coins", sdk.NewCoins(sdk.NewInt64Coin("aaa", 10), sdk.NewInt64Coin("bbb", 5)), false, false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := simulation.RandomFees(r, sdk.Context{}, tt.spendableCoins)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("RandomFees() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			require.Equal(t, tt.wantEmpty, got.Empty())
+		})
+	}
+}
diff --git a/x/simulation/rand_util_test.go b/x/simulation/rand_util_test.go
index e212fed0a..2128de405 100644
--- a/x/simulation/rand_util_test.go
+++ b/x/simulation/rand_util_test.go
@@ -3,6 +3,7 @@ package simulation_test
 import (
 	"math/rand"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/require"
 
@@ -11,6 +12,7 @@ import (
 )
 
 func TestRandSubsetCoins(t *testing.T) {
+	t.Parallel()
 	tests := []struct {
 		name  string
 		r     *rand.Rand
@@ -31,6 +33,26 @@ func TestRandSubsetCoins(t *testing.T) {
 	}
 }
 
+func TestRandStringOfLength(t *testing.T) {
+	t.Parallel()
+	r := rand.New(rand.NewSource(time.Now().Unix()))
+	tests := []struct {
+		name string
+		n    int
+		want int
+	}{
+		{"0-size", 0, 0},
+		{"10-size", 10, 10},
+		{"10-size", 1_000_000_000, 1_000_000_000},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := simulation.RandStringOfLength(r, tt.n)
+			require.Equal(t, tt.want, len(got))
+		})
+	}
+}
+
 func mustParseCoins(s string) sdk.Coins {
 	coins, err := sdk.ParseCoins(s)
 	if err != nil {