From f9e3b0a3c21a2d2ba3a298a4957184b15ae37c32 Mon Sep 17 00:00:00 2001
From: terencechain <terence@prysmaticlabs.com>
Date: Sat, 11 Jun 2022 08:54:33 -0700
Subject: [PATCH] Active balance: return `EFFECTIVE_BALANCE_INCREMENT` as min
 (#10866)

---
 .../core/helpers/rewards_penalties.go         |  2 ++
 .../core/helpers/rewards_penalties_test.go    | 21 +++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/beacon-chain/core/helpers/rewards_penalties.go b/beacon-chain/core/helpers/rewards_penalties.go
index 25c63f1ff..1cae465b7 100644
--- a/beacon-chain/core/helpers/rewards_penalties.go
+++ b/beacon-chain/core/helpers/rewards_penalties.go
@@ -76,6 +76,8 @@ func TotalActiveBalance(s state.ReadOnlyBeaconState) (uint64, error) {
 		return 0, err
 	}
 
+	// Spec defines `EffectiveBalanceIncrement` as min to avoid divisions by zero.
+	total = mathutil.Max(params.BeaconConfig().EffectiveBalanceIncrement, total)
 	if err := balanceCache.AddTotalEffectiveBalance(s, total); err != nil {
 		return 0, err
 	}
diff --git a/beacon-chain/core/helpers/rewards_penalties_test.go b/beacon-chain/core/helpers/rewards_penalties_test.go
index 4dd8b3c27..63ccfd1ab 100644
--- a/beacon-chain/core/helpers/rewards_penalties_test.go
+++ b/beacon-chain/core/helpers/rewards_penalties_test.go
@@ -74,6 +74,27 @@ func TestTotalActiveBalance(t *testing.T) {
 	}
 }
 
+func TestTotalActiveBal_ReturnMin(t *testing.T) {
+	tests := []struct {
+		vCount int
+	}{
+		{1},
+		{10},
+		{10000},
+	}
+	for _, test := range tests {
+		validators := make([]*ethpb.Validator, 0)
+		for i := 0; i < test.vCount; i++ {
+			validators = append(validators, &ethpb.Validator{EffectiveBalance: 1, ExitEpoch: 1})
+		}
+		state, err := v1.InitializeFromProto(&ethpb.BeaconState{Validators: validators})
+		require.NoError(t, err)
+		bal, err := TotalActiveBalance(state)
+		require.NoError(t, err)
+		require.Equal(t, params.BeaconConfig().EffectiveBalanceIncrement, bal)
+	}
+}
+
 func TestTotalActiveBalance_WithCache(t *testing.T) {
 	tests := []struct {
 		vCount    int