diff --git a/consensus/pol.go b/consensus/pol.go
index 9725a7bb4..eca67b646 100644
--- a/consensus/pol.go
+++ b/consensus/pol.go
@@ -79,6 +79,9 @@ func (pol *POL) Verify(vset *state.ValidatorSet) error {
 		if val == nil {
 			return Errorf("Invalid validator for commit %v for POL %v", sig, pol)
 		}
+		if round >= pol.Round {
+			return Errorf("Invalid commit round %v for POL %v", round, pol)
+		}
 
 		commitDoc := BinaryBytes(&Vote{Height: pol.Height, Round: round,
 			Type: VoteTypeCommit, BlockHash: pol.BlockHash}) // TODO cache
diff --git a/consensus/pol_test.go b/consensus/pol_test.go
new file mode 100644
index 000000000..db622c1d7
--- /dev/null
+++ b/consensus/pol_test.go
@@ -0,0 +1,196 @@
+package consensus
+
+import (
+	. "github.com/tendermint/tendermint/blocks"
+	. "github.com/tendermint/tendermint/common"
+
+	"bytes"
+	"testing"
+)
+
+// NOTE: see consensus/test.go for common test methods.
+
+func TestVerifyVotes(t *testing.T) {
+	_, valSet, privAccounts := makeVoteSet(0, 0, 10, 1)
+
+	// Make a POL with -2/3 votes.
+	blockHash := RandBytes(32)
+	pol := &POL{
+		Height: 0, Round: 0, BlockHash: blockHash,
+	}
+	vote := &Vote{
+		Height: 0, Round: 0, Type: VoteTypeBare, BlockHash: blockHash,
+	}
+	for i := 0; i < 6; i++ {
+		privAccounts[i].Sign(vote)
+		pol.Votes = append(pol.Votes, vote.Signature)
+	}
+
+	// Check that validation fails.
+	if err := pol.Verify(valSet); err == nil {
+		t.Errorf("Expected POL.Verify() to fail, not enough votes.")
+	}
+
+	// Make a POL with +2/3 votes.
+	privAccounts[7].Sign(vote)
+	pol.Votes = append(pol.Votes, vote.Signature)
+
+	// Check that validation succeeds.
+	if err := pol.Verify(valSet); err != nil {
+		t.Errorf("Expected POL.Verify() to succeed")
+	}
+}
+
+func TestVerifyInvalidVote(t *testing.T) {
+	_, valSet, privAccounts := makeVoteSet(0, 0, 10, 1)
+
+	// Make a POL with +2/3 votes with the wrong signature.
+	blockHash := RandBytes(32)
+	pol := &POL{
+		Height: 0, Round: 0, BlockHash: blockHash,
+	}
+	vote := &Vote{
+		Height: 0, Round: 0, Type: VoteTypeBare, BlockHash: blockHash,
+	}
+	for i := 0; i < 7; i++ {
+		privAccounts[i].Sign(vote)
+		// Mutate the signature.
+		vote.Signature.Bytes[0] += byte(0x01)
+		pol.Votes = append(pol.Votes, vote.Signature)
+	}
+
+	// Check that validation fails.
+	if err := pol.Verify(valSet); err == nil {
+		t.Errorf("Expected POL.Verify() to fail, wrong signatures.")
+	}
+}
+
+func TestVerifyCommits(t *testing.T) {
+	_, valSet, privAccounts := makeVoteSet(0, 2, 10, 1)
+
+	// Make a POL with +2/3 votes.
+	blockHash := RandBytes(32)
+	pol := &POL{
+		Height: 0, Round: 2, BlockHash: blockHash,
+	}
+	vote := &Vote{
+		Height: 0, Round: 1, Type: VoteTypeCommit, BlockHash: blockHash,
+	}
+	for i := 0; i < 7; i++ {
+		privAccounts[i].Sign(vote)
+		pol.Commits = append(pol.Commits, vote.Signature)
+		pol.CommitRounds = append(pol.CommitRounds, 1)
+	}
+
+	// Check that validation succeeds.
+	if err := pol.Verify(valSet); err != nil {
+		t.Errorf("Expected POL.Verify() to succeed")
+	}
+}
+
+func TestVerifyInvalidCommits(t *testing.T) {
+	_, valSet, privAccounts := makeVoteSet(0, 2, 10, 1)
+
+	// Make a POL with +2/3 votes with the wrong signature.
+	blockHash := RandBytes(32)
+	pol := &POL{
+		Height: 0, Round: 2, BlockHash: blockHash,
+	}
+	vote := &Vote{
+		Height: 0, Round: 1, Type: VoteTypeCommit, BlockHash: blockHash,
+	}
+	for i := 0; i < 7; i++ {
+		privAccounts[i].Sign(vote)
+		// Mutate the signature.
+		vote.Signature.Bytes[0] += byte(0x01)
+		pol.Commits = append(pol.Commits, vote.Signature)
+		pol.CommitRounds = append(pol.CommitRounds, 1)
+	}
+
+	// Check that validation fails.
+	if err := pol.Verify(valSet); err == nil {
+		t.Errorf("Expected POL.Verify() to fail, wrong signatures.")
+	}
+}
+
+func TestVerifyInvalidCommitRounds(t *testing.T) {
+	_, valSet, privAccounts := makeVoteSet(0, 2, 10, 1)
+
+	// Make a POL with +2/3 commits for the current round.
+	blockHash := RandBytes(32)
+	pol := &POL{
+		Height: 0, Round: 2, BlockHash: blockHash,
+	}
+	vote := &Vote{
+		Height: 0, Round: 2, Type: VoteTypeCommit, BlockHash: blockHash,
+	}
+	for i := 0; i < 7; i++ {
+		privAccounts[i].Sign(vote)
+		pol.Commits = append(pol.Commits, vote.Signature)
+		pol.CommitRounds = append(pol.CommitRounds, 2)
+	}
+
+	// Check that validation fails.
+	if err := pol.Verify(valSet); err == nil {
+		t.Errorf("Expected POL.Verify() to fail, same round.")
+	}
+}
+
+func TestVerifyInvalidCommitRounds2(t *testing.T) {
+	_, valSet, privAccounts := makeVoteSet(0, 2, 10, 1)
+
+	// Make a POL with +2/3 commits for future round.
+	blockHash := RandBytes(32)
+	pol := &POL{
+		Height: 0, Round: 2, BlockHash: blockHash,
+	}
+	vote := &Vote{
+		Height: 0, Round: 3, Type: VoteTypeCommit, BlockHash: blockHash,
+	}
+	for i := 0; i < 7; i++ {
+		privAccounts[i].Sign(vote)
+		pol.Commits = append(pol.Commits, vote.Signature)
+		pol.CommitRounds = append(pol.CommitRounds, 3)
+	}
+
+	// Check that validation fails.
+	if err := pol.Verify(valSet); err == nil {
+		t.Errorf("Expected POL.Verify() to fail, future round.")
+	}
+}
+
+func TestReadWrite(t *testing.T) {
+	_, valSet, privAccounts := makeVoteSet(0, 0, 10, 1)
+
+	// Make a POL with +2/3 votes.
+	blockHash := RandBytes(32)
+	pol := &POL{
+		Height: 0, Round: 0, BlockHash: blockHash,
+	}
+	vote := &Vote{
+		Height: 0, Round: 0, Type: VoteTypeBare, BlockHash: blockHash,
+	}
+	for i := 0; i < 7; i++ {
+		privAccounts[i].Sign(vote)
+		pol.Votes = append(pol.Votes, vote.Signature)
+	}
+
+	// Write it to a buffer.
+	buf := new(bytes.Buffer)
+	_, err := pol.WriteTo(buf)
+	if err != nil {
+		t.Fatalf("Failed to write POL")
+	}
+
+	// Read from buffer.
+	var n int64
+	pol2 := ReadPOL(buf, &n, &err)
+	if err != nil {
+		t.Fatalf("Failed to read POL")
+	}
+
+	// Check that validation succeeds.
+	if err := pol2.Verify(valSet); err != nil {
+		t.Errorf("Expected POL.Verify() to succeed")
+	}
+}
diff --git a/consensus/test.go b/consensus/test.go
new file mode 100644
index 000000000..147282d73
--- /dev/null
+++ b/consensus/test.go
@@ -0,0 +1,27 @@
+package consensus
+
+import (
+	. "github.com/tendermint/tendermint/blocks"
+	"github.com/tendermint/tendermint/state"
+)
+
+func makeValidator(id uint64, votingPower uint64) (*state.Validator, *state.PrivAccount) {
+	privAccount := state.GenPrivAccount()
+	privAccount.Id = id
+	return &state.Validator{
+		Account:     privAccount.Account,
+		VotingPower: votingPower,
+	}, privAccount
+}
+
+func makeVoteSet(height uint32, round uint16, numValidators int, votingPower uint64) (*VoteSet, *state.ValidatorSet, []*state.PrivAccount) {
+	vals := make([]*state.Validator, numValidators)
+	privAccounts := make([]*state.PrivAccount, numValidators)
+	for i := 0; i < numValidators; i++ {
+		val, privAccount := makeValidator(uint64(i), votingPower)
+		vals[i] = val
+		privAccounts[i] = privAccount
+	}
+	valSet := state.NewValidatorSet(vals)
+	return NewVoteSet(height, round, VoteTypeBare, valSet), valSet, privAccounts
+}
diff --git a/consensus/vote_set_test.go b/consensus/vote_set_test.go
index 4a760b998..d235ea4f7 100644
--- a/consensus/vote_set_test.go
+++ b/consensus/vote_set_test.go
@@ -3,31 +3,11 @@ package consensus
 import (
 	. "github.com/tendermint/tendermint/blocks"
 	. "github.com/tendermint/tendermint/common"
-	"github.com/tendermint/tendermint/state"
 
 	"testing"
 )
 
-func makeValidator(id uint64, votingPower uint64) (*state.Validator, *state.PrivAccount) {
-	privAccount := state.GenPrivAccount()
-	privAccount.Id = id
-	return &state.Validator{
-		Account:     privAccount.Account,
-		VotingPower: votingPower,
-	}, privAccount
-}
-
-func makeVoteSet(height uint32, round uint16, numValidators int, votingPower uint64) (*VoteSet, *state.ValidatorSet, []*state.PrivAccount) {
-	vals := make([]*state.Validator, numValidators)
-	privAccounts := make([]*state.PrivAccount, numValidators)
-	for i := 0; i < numValidators; i++ {
-		val, privAccount := makeValidator(uint64(i), votingPower)
-		vals[i] = val
-		privAccounts[i] = privAccount
-	}
-	valSet := state.NewValidatorSet(vals)
-	return NewVoteSet(height, round, VoteTypeBare, valSet), valSet, privAccounts
-}
+// NOTE: see consensus/test.go for common test methods.
 
 func TestAddVote(t *testing.T) {
 	voteSet, _, privAccounts := makeVoteSet(0, 0, 10, 1)