@@ -27,7 +27,7 @@ }
 
 // NewBatchBuilder constructs a new BatchBuilder, and executes the bb.Reset
 // method
-func NewBatchBuilder(dbpath string, synchronizerStateDB *statedb.StateDB, configCircuits []ConfigCircuit, batchNum uint64, nLevels uint64) (*BatchBuilder, error) {
+func NewBatchBuilder(dbpath string, synchronizerStateDB *statedb.StateDB, configCircuits []ConfigCircuit, batchNum common.BatchNum, nLevels uint64) (*BatchBuilder, error) {
 	localStateDB, err := statedb.NewLocalStateDB(dbpath, synchronizerStateDB, true, int(nLevels))
 	if err != nil {
 		return nil, err
@@ -46,12 +46,16 @@ // Reset tells the BatchBuilder to reset it's internal state to the required
 // `batchNum`.  If `fromSynchronizer` is true, the BatchBuilder must take a
 // copy of the rollup state from the Synchronizer at that `batchNum`, otherwise
 // it can just roll back the internal copy.
-func (bb *BatchBuilder) Reset(batchNum uint64, fromSynchronizer bool) error {
+func (bb *BatchBuilder) Reset(batchNum common.BatchNum, fromSynchronizer bool) error {
 	return bb.localStateDB.Reset(batchNum, fromSynchronizer)
 }
 
 // BuildBatch takes the transactions and returns the common.ZKInputs of the next batch
 func (bb *BatchBuilder) BuildBatch(configBatch *ConfigBatch, l1usertxs, l1coordinatortxs []*common.L1Tx, l2txs []*common.L2Tx, tokenIDs []common.TokenID) (*common.ZKInputs, error) {
 	zkInputs, _, err := bb.localStateDB.ProcessTxs(false, l1usertxs, l1coordinatortxs, l2txs)
+	if err != nil {
+		return nil, err
+	}
+	err = bb.localStateDB.MakeCheckpoint()
 	return zkInputs, err
 }

@@ -1,7 +1,6 @@
 package batchbuilder
 
 import (
-	"fmt"
 	"io/ioutil"
 	"testing"
 
@@ -19,7 +18,6 @@ assert.Nil(t, err)
 
 	bbDir, err := ioutil.TempDir("", "tmpBatchBuilderDB")
 	require.Nil(t, err)
-	bb, err := NewBatchBuilder(bbDir, synchDB, nil, 0, 32)
+	_, err = NewBatchBuilder(bbDir, synchDB, nil, 0, 32)
 	assert.Nil(t, err)
-	fmt.Println(bb)
 }

@@ -2,11 +2,13 @@ package common
 
 import (
 	"math/big"
+
+	"github.com/iden3/go-merkletree"
 )
 
 type ExitInfo struct {
 	AccountIdx  Idx
-	MerkleProof []byte
+	MerkleProof *merkletree.CircomVerifierProof
 	Balance     *big.Int
 	Nullifier   *big.Int
 }

@@ -10,7 +10,7 @@ }
 
 // BatchInfo contans the Batch information
 type BatchInfo struct {
-	batchNum       uint64
+	batchNum       common.BatchNum
 	serverProof    *ServerProofInfo
 	zkInputs       *common.ZKInputs
 	proof          *Proof
@@ -22,7 +22,7 @@ }
 
 // NewBatchInfo creates a new BatchInfo with the given batchNum &
 // ServerProofInfo
-func NewBatchInfo(batchNum uint64, serverProof *ServerProofInfo) BatchInfo {
+func NewBatchInfo(batchNum common.BatchNum, serverProof *ServerProofInfo) BatchInfo {
 	return BatchInfo{
 		batchNum:    batchNum,
 		serverProof: serverProof,

@@ -3,6 +3,7 @@
 import (
 	"testing"
 
+	"github.com/hermeznetwork/hermez-node/common"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -19,8 +20,8 @@ bq.Push(&BatchInfo{
 		batchNum: 1,
 	})
 
-	assert.Equal(t, uint64(0), bq.Pop().batchNum)
-	assert.Equal(t, uint64(2), bq.Pop().batchNum)
-	assert.Equal(t, uint64(1), bq.Pop().batchNum)
+	assert.Equal(t, common.BatchNum(0), bq.Pop().batchNum)
+	assert.Equal(t, common.BatchNum(2), bq.Pop().batchNum)
+	assert.Equal(t, common.BatchNum(1), bq.Pop().batchNum)
 	assert.Nil(t, bq.Pop())
 }

@@ -6,7 +6,9 @@
 	ethCommon "github.com/ethereum/go-ethereum/common"
 	"github.com/hermeznetwork/hermez-node/batchbuilder"
 	"github.com/hermeznetwork/hermez-node/common"
+	"github.com/hermeznetwork/hermez-node/db/historydb"
 	"github.com/hermeznetwork/hermez-node/eth"
+	"github.com/hermeznetwork/hermez-node/log"
 	"github.com/hermeznetwork/hermez-node/txselector"
 	kvdb "github.com/iden3/go-merkletree/db"
 	"github.com/iden3/go-merkletree/db/memory"
@@ -15,17 +17,26 @@
 // CoordinatorConfig contains the Coordinator configuration
 type CoordinatorConfig struct {
 	ForgerAddress ethCommon.Address
+	LoopInterval  time.Duration
 }
 
 // Coordinator implements the Coordinator type
 type Coordinator struct {
+	// m            sync.Mutex
+	stopch       chan bool
+	stopforgerch chan bool
+
+	forging    bool
+	isForgeSeq bool // WIP just for testing while implementing
+
 	config CoordinatorConfig
 
-	batchNum        uint64
+	batchNum        common.BatchNum
 	batchQueue      *BatchQueue
 	serverProofPool ServerProofPool
 
 	// synchronizer *synchronizer.Synchronizer
+	hdb          *historydb.HistoryDB
 	txsel        *txselector.TxSelector
 	batchBuilder *batchbuilder.BatchBuilder
 
@@ -34,48 +45,121 @@ ethTxStore kvdb.Storage
 }
 
 // NewCoordinator creates a new Coordinator
-func NewCoordinator() *Coordinator { // once synchronizer is ready, synchronizer.Synchronizer will be passed as parameter here
-	var c *Coordinator
-	// c.ethClient = eth.NewClient() // TBD
-	c.ethTxStore = memory.NewMemoryStorage()
-	return c
+func NewCoordinator(conf CoordinatorConfig,
+	hdb *historydb.HistoryDB,
+	txsel *txselector.TxSelector,
+	bb *batchbuilder.BatchBuilder,
+	ethClient *eth.Client) *Coordinator { // once synchronizer is ready, synchronizer.Synchronizer will be passed as parameter here
+	c := Coordinator{
+		config:       conf,
+		hdb:          hdb,
+		txsel:        txsel,
+		batchBuilder: bb,
+		ethClient:    ethClient,
+		ethTxStore:   memory.NewMemoryStorage(),
+	}
+	return &c
+}
+
+func (c *Coordinator) Stop() {
+	log.Info("Stopping Coordinator")
+	c.stopch <- true
 }
 
 // Start starts the Coordinator service
 func (c *Coordinator) Start() {
-	// TODO TBD note: the sequences & loops & errors & logging & goroutines
-	// & channels approach still needs to be defined, the current code is a
-	// wip draft
+	c.stopch = make(chan bool) // initialize channel
+	go func() {
+		log.Info("Starting Coordinator")
+		for {
+			select {
+			case <-c.stopch:
+				close(c.stopforgerch)
+				log.Info("Coordinator stopped")
+				return
+			case <-time.After(c.config.LoopInterval):
+				if !c.isForgeSequence() {
+					if c.forging {
+						log.Info("forging stopped")
+						c.forging = false
+						close(c.stopforgerch)
+					}
+					log.Debug("not in forge time")
+					continue
+				}
+				if !c.forging {
+					log.Info("Start Forging")
+					// c.batchNum = c.hdb.GetLastBatchNum() // uncomment when HistoryDB is ready
+					err := c.txsel.Reset(c.batchNum)
+					if err != nil {
+						log.Error("forging err: ", err)
+					}
+					err = c.batchBuilder.Reset(c.batchNum, true)
+					if err != nil {
+						log.Error("forging err: ", err)
+					}
+					c.batchQueue = NewBatchQueue()
 
-	// TBD: goroutines strategy
+					c.forgerLoop()
+					c.forging = true
+				}
+			}
+		}
+	}()
+}
+
+// forgerLoop trigers goroutines for:
+// - forgeSequence
+// - proveSequence
+// - forgeConfirmationSequence
+func (c *Coordinator) forgerLoop() {
+	c.stopforgerch = make(chan bool) // initialize channel
 
-	// if in Forge Sequence:
-	if c.isForgeSequence() {
-		// c.batchNum = c.synchronizer.LastBatchNum()
-		_ = c.txsel.Reset(c.batchNum)
-		_ = c.batchBuilder.Reset(c.batchNum, true)
-		c.batchQueue = NewBatchQueue()
-		go func() {
-			for {
-				_ = c.forgeSequence()
-				time.Sleep(1 * time.Second)
+	go func() {
+		log.Info("forgeSequence started")
+		for {
+			select {
+			case <-c.stopforgerch:
+				log.Info("forgeSequence stopped")
+				return
+			case <-time.After(c.config.LoopInterval):
+				if err := c.forgeSequence(); err != nil {
+					log.Error("forgeSequence err: ", err)
+				}
 			}
-		}()
-		go func() {
-			for {
-				_ = c.proveSequence()
-				time.Sleep(1 * time.Second)
+		}
+	}()
+	go func() {
+		log.Info("proveSequence started")
+		for {
+			select {
+			case <-c.stopforgerch:
+				log.Info("proveSequence stopped")
+				return
+			case <-time.After(c.config.LoopInterval):
+				if err := c.proveSequence(); err != nil && err != common.ErrBatchQueueEmpty {
+					log.Error("proveSequence err: ", err)
+				}
 			}
-		}()
-		go func() {
-			for {
-				_ = c.forgeConfirmationSequence()
-				time.Sleep(1 * time.Second)
+		}
+	}()
+	go func() {
+		log.Info("forgeConfirmationSequence started")
+		for {
+			select {
+			case <-c.stopforgerch:
+				log.Info("forgeConfirmationSequence stopped")
+				return
+			case <-time.After(c.config.LoopInterval):
+				if err := c.forgeConfirmationSequence(); err != nil {
+					log.Error("forgeConfirmationSequence err: ", err)
+				}
 			}
-		}()
-	}
+		}
+	}()
 }
 
+// forgeSequence
 func (c *Coordinator) forgeSequence() error {
 	// TODO once synchronizer has this method ready:
 	// If there's been a reorg, handle it
@@ -104,8 +188,8 @@ var l1UserTxsExtra, l1OperatorTxs []*common.L1Tx
 	// 1. Decide if we forge L2Tx or L1+L2Tx
 	if c.shouldL1L2Batch() {
 		// 2a: L1+L2 txs
-		// l1UserTxs, toForgeL1TxsNumber := c.synchronizer.GetNextL1UserTxs() // TODO once synchronizer is ready, uncomment
-		var l1UserTxs []*common.L1Tx = nil                                                                // tmp, depends on synchronizer
+		// l1UserTxs, toForgeL1TxsNumber := c.hdb.GetNextL1UserTxs() // TODO once HistoryDB is ready, uncomment
+		var l1UserTxs []*common.L1Tx = nil                                                                // tmp, depends on HistoryDB
 		l1UserTxsExtra, l1OperatorTxs, poolL2Txs, err = c.txsel.GetL1L2TxSelection(c.batchNum, l1UserTxs) // TODO once feesInfo is added to method return, add the var
 		if err != nil {
 			return err
@@ -144,6 +228,7 @@ }
 
 	// 5. Save metadata from BatchBuilder output for BatchNum
 	batchInfo.SetZKInputs(zkInputs)
+	log.Debugf("Batch builded, batchNum: %d ", c.batchNum)
 
 	// 6. Call an idle server proof with BatchBuilder output, save server proof info for batchNum
 	err = batchInfo.serverProof.CalculateProof(zkInputs)
@@ -160,6 +245,7 @@ func (c *Coordinator) proveSequence() error {
 	batchInfo := c.batchQueue.Pop()
 	if batchInfo == nil {
 		// no batches in queue, return
+		log.Debug("not batch to prove yet")
 		return common.ErrBatchQueueEmpty
 	}
 	serverProofInfo := batchInfo.serverProof
@@ -173,6 +259,8 @@ _, err = c.ethClient.ForgeCall(callData)
 	if err != nil {
 		return err
 	}
+	log.Debugf("ethClient ForgeCall sent, batchNum: %d", c.batchNum)
+
 	// TODO once tx data type is defined, store ethTx (returned by ForgeCall)
 	// TBD if use ethTxStore as a disk k-v database, or use a Queue
 	// tx, err := c.ethTxStore.NewTx()
@@ -202,8 +290,7 @@ }
 
 // isForgeSequence returns true if the node is the Forger in the current ethereum block
 func (c *Coordinator) isForgeSequence() bool {
-
-	return false
+	return c.isForgeSeq
 }
 
 func (c *Coordinator) purgeRemoveByTimeout() error {

@@ -0,0 +1,76 @@
+package coordinator
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/hermeznetwork/hermez-node/batchbuilder"
+	"github.com/hermeznetwork/hermez-node/db/historydb"
+	"github.com/hermeznetwork/hermez-node/db/l2db"
+	"github.com/hermeznetwork/hermez-node/db/statedb"
+	"github.com/hermeznetwork/hermez-node/log"
+	"github.com/hermeznetwork/hermez-node/txselector"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func newTestModules(t *testing.T) (*txselector.TxSelector, *batchbuilder.BatchBuilder) { // FUTURE once Synchronizer is ready, should return it also
+	nLevels := 32
+
+	synchDB, err := ioutil.TempDir("", "tmpSynchDB")
+	require.Nil(t, err)
+	sdb, err := statedb.NewStateDB(synchDB, true, nLevels)
+	assert.Nil(t, err)
+
+	pass := os.Getenv("POSTGRES_PASS")
+	l2DB, err := l2db.NewL2DB(5432, "localhost", "hermez", pass, "l2", 10, 512, 24*time.Hour)
+	require.Nil(t, err)
+
+	txselDir, err := ioutil.TempDir("", "tmpTxSelDB")
+	require.Nil(t, err)
+	txsel, err := txselector.NewTxSelector(txselDir, sdb, l2DB, 10, 10, 10)
+	assert.Nil(t, err)
+
+	bbDir, err := ioutil.TempDir("", "tmpBatchBuilderDB")
+	require.Nil(t, err)
+	bb, err := batchbuilder.NewBatchBuilder(bbDir, sdb, nil, 0, uint64(nLevels))
+	assert.Nil(t, err)
+
+	// l1Txs, coordinatorL1Txs, poolL2Txs := test.GenerateTestTxsFromSet(t, test.SetTest0)
+
+	return txsel, bb
+}
+
+func TestCoordinator(t *testing.T) {
+	txsel, bb := newTestModules(t)
+
+	conf := CoordinatorConfig{
+		LoopInterval: 100 * time.Millisecond,
+	}
+	hdb := &historydb.HistoryDB{}
+	c := NewCoordinator(conf, hdb, txsel, bb, nil)
+	c.Start()
+	time.Sleep(1 * time.Second)
+
+	// simulate forgeSequence time
+	log.Debug("simulate entering in forge time")
+	c.isForgeSeq = true
+	time.Sleep(1 * time.Second)
+
+	// simulate going out from forgeSequence
+	log.Debug("simulate going out from forge time")
+	c.isForgeSeq = false
+	time.Sleep(1 * time.Second)
+
+	// simulate entering forgeSequence time again
+	log.Debug("simulate entering in forge time again")
+	c.isForgeSeq = true
+	time.Sleep(1 * time.Second)
+
+	// simulate stopping forgerLoop by channel
+	log.Debug("simulate stopping forgerLoop by closing coordinator stopch")
+	c.Stop()
+	time.Sleep(1 * time.Second)
+}

@@ -130,7 +130,7 @@ return nil
 }
 
 // DeleteCheckpoint removes if exist the checkpoint of the given batchNum
-func (s *StateDB) DeleteCheckpoint(batchNum uint64) error {
+func (s *StateDB) DeleteCheckpoint(batchNum common.BatchNum) error {
 	checkpointPath := s.path + PATHBATCHNUM + strconv.Itoa(int(batchNum))
 
 	if _, err := os.Stat(checkpointPath); os.IsNotExist(err) {
@@ -144,7 +144,7 @@ // Reset resets the StateDB to the checkpoint at the given batchNum. Reset
 // does not delete the checkpoints between old current and the new current,
 // those checkpoints will remain in the storage, and eventually will be
 // deleted when MakeCheckpoint overwrites them.
-func (s *StateDB) Reset(batchNum uint64) error {
+func (s *StateDB) Reset(batchNum common.BatchNum) error {
 	if batchNum == 0 {
 		s.idx = 0
 		return nil
@@ -331,7 +331,7 @@ }
 
 // Reset performs a reset in the LocaStateDB. If fromSynchronizer is true, it
 // gets the state from LocalStateDB.synchronizerStateDB for the given batchNum. If fromSynchronizer is false, get the state from LocalStateDB checkpoints.
-func (l *LocalStateDB) Reset(batchNum uint64, fromSynchronizer bool) error {
+func (l *LocalStateDB) Reset(batchNum common.BatchNum, fromSynchronizer bool) error {
 	if batchNum == 0 {
 		l.idx = 0
 		return nil

@@ -193,13 +193,13 @@ cb, err = sdb.GetCurrentBatch()
 	assert.Nil(t, err)
 	assert.Equal(t, common.BatchNum(4), cb)
 
-	err = sdb.DeleteCheckpoint(uint64(9))
+	err = sdb.DeleteCheckpoint(common.BatchNum(9))
 	assert.Nil(t, err)
-	err = sdb.DeleteCheckpoint(uint64(10))
+	err = sdb.DeleteCheckpoint(common.BatchNum(10))
 	assert.Nil(t, err)
-	err = sdb.DeleteCheckpoint(uint64(9)) // does not exist, should return err
+	err = sdb.DeleteCheckpoint(common.BatchNum(9)) // does not exist, should return err
 	assert.NotNil(t, err)
-	err = sdb.DeleteCheckpoint(uint64(11)) // does not exist, should return err
+	err = sdb.DeleteCheckpoint(common.BatchNum(11)) // does not exist, should return err
 	assert.NotNil(t, err)
 
 	// Create a LocalStateDB from the initial StateDB

@@ -13,20 +13,12 @@
 // keyidx is used as key in the db to store the current Idx
 var keyidx = []byte("idx")
 
-// FUTURE This will be used from common once pending PR is merged
-type ExitInfo struct {
-	Idx       *common.Idx
-	Proof     *merkletree.CircomVerifierProof
-	Nullifier *big.Int
-	Balance   *big.Int
-}
-
 // ProcessTxs process the given L1Txs & L2Txs applying the needed updates to
 // the StateDB depending on the transaction Type. Returns the common.ZKInputs
 // to generate the SnarkProof later used by the BatchBuilder, and if
 // cmpExitTree is set to true, returns common.ExitTreeLeaf that is later used
 // by the Synchronizer to update the HistoryDB.
-func (s *StateDB) ProcessTxs(cmpExitTree bool, l1usertxs, l1coordinatortxs []*common.L1Tx, l2txs []*common.L2Tx) (*common.ZKInputs, []*ExitInfo, error) {
+func (s *StateDB) ProcessTxs(cmpExitTree bool, l1usertxs, l1coordinatortxs []*common.L1Tx, l2txs []*common.L2Tx) (*common.ZKInputs, []*common.ExitInfo, error) {
 	var err error
 	var exitTree *merkletree.MerkleTree
 	exits := make(map[common.Idx]common.Account)
@@ -71,8 +63,8 @@ return nil, nil, nil
 	}
 
 	// once all txs processed (exitTree root frozen), for each leaf
-	// generate ExitInfo data
-	var exitInfos []*ExitInfo
+	// generate common.ExitInfo data
+	var exitInfos []*common.ExitInfo
 	for exitIdx, exitAccount := range exits {
 		// 0. generate MerkleProof
 		p, err := exitTree.GenerateCircomVerifierProof(exitIdx.BigInt(), nil)
@@ -92,12 +84,12 @@ })
 		if err != nil {
 			return nil, nil, err
 		}
-		// 2. generate ExitInfo
-		ei := &ExitInfo{
-			Idx:       &exitIdx,
-			Proof:     p,
-			Nullifier: nullifier,
-			Balance:   exitAccount.Balance,
+		// 2. generate common.ExitInfo
+		ei := &common.ExitInfo{
+			AccountIdx:  exitIdx,
+			MerkleProof: p,
+			Nullifier:   nullifier,
+			Balance:     exitAccount.Balance,
 		}
 		exitInfos = append(exitInfos, ei)
 	}

@@ -195,9 +195,18 @@ func (c *Client) HeaderByNumber(ctx context.Context, number *big.Int) (*types.Header, error) {
 	return c.client.HeaderByNumber(ctx, number)
 }
 
-// BlockByNumber internally calls ethclient.Client BlockByNumber
-func (c *Client) BlockByNumber(ctx context.Context, number *big.Int) (*types.Block, error) {
-	return c.client.BlockByNumber(ctx, number)
+// BlockByNumber internally calls ethclient.Client BlockByNumber and returns *common.Block
+func (c *Client) BlockByNumber(ctx context.Context, number *big.Int) (*common.Block, error) {
+	block, err := c.client.BlockByNumber(ctx, number)
+	if err != nil {
+		return nil, err
+	}
+	b := &common.Block{
+		EthBlockNum: block.Number().Uint64(),
+		Timestamp:   time.Unix(int64(block.Time()), 0),
+		Hash:        block.Hash(),
+	}
+	return b, nil
 }
 
 func (c *Client) ForgeCall(callData *common.CallDataForge) ([]byte, error) {

@@ -57,7 +57,8 @@ panic(err)
 	}
 	//nolint:errcheck
 	defer logger.Sync()
-	log = logger.Sugar()
+	withOptions := logger.WithOptions(zap.AddCallerSkip(1))
+	log = withOptions.Sugar()
 
 	if errorsPath != "" {
 		log.Infof("file where errors will be written: %s", errorsPath)

@@ -4,6 +4,7 @@ import (
 	"crypto/ecdsa"
 	"math/big"
 	"strconv"
+	"strings"
 	"testing"
 	"time"
 
@@ -11,6 +12,7 @@ ethCommon "github.com/ethereum/go-ethereum/common"
 	ethCrypto "github.com/ethereum/go-ethereum/crypto"
 	"github.com/hermeznetwork/hermez-node/common"
 	"github.com/iden3/go-iden3-crypto/babyjub"
+	"github.com/stretchr/testify/require"
 )
 
 type Account struct {
@@ -53,12 +55,12 @@ func GenerateTestTxs(t *testing.T, instructions Instructions) ([][]*common.L1Tx, [][]*common.L1Tx, [][]*common.PoolL2Tx) {
 	accounts := GenerateKeys(t, instructions.Accounts)
 	l1CreatedAccounts := make(map[string]*Account)
 
-	var batchL1txs []*common.L1Tx
-	var batchCoordinatorL1txs []*common.L1Tx
-	var batchL2txs []*common.PoolL2Tx
-	var l1txs [][]*common.L1Tx
-	var coordinatorL1txs [][]*common.L1Tx
-	var l2txs [][]*common.PoolL2Tx
+	var batchL1Txs []*common.L1Tx
+	var batchCoordinatorL1Txs []*common.L1Tx
+	var batchPoolL2Txs []*common.PoolL2Tx
+	var l1Txs [][]*common.L1Tx
+	var coordinatorL1Txs [][]*common.L1Tx
+	var poolL2Txs [][]*common.PoolL2Tx
 	idx := 1
 	for _, inst := range instructions.Instructions {
 		switch inst.Type {
@@ -71,7 +73,7 @@ TokenID:     inst.TokenID,
 				LoadAmount:  big.NewInt(int64(inst.Amount)),
 				Type:        common.TxTypeCreateAccountDeposit,
 			}
-			batchL1txs = append(batchL1txs, &tx)
+			batchL1Txs = append(batchL1Txs, &tx)
 			if accounts[idxTokenIDToString(inst.From, inst.TokenID)].Idx == common.Idx(0) { // if account.Idx is not set yet, set it and increment idx
 				accounts[idxTokenIDToString(inst.From, inst.TokenID)].Idx = common.Idx(idx)
 
@@ -90,7 +92,7 @@ Type:        common.TxTypeCreateAccountDeposit,
 				}
 				accounts[idxTokenIDToString(inst.To, inst.TokenID)].Idx = common.Idx(idx)
 				l1CreatedAccounts[idxTokenIDToString(inst.To, inst.TokenID)] = accounts[idxTokenIDToString(inst.To, inst.TokenID)]
-				batchCoordinatorL1txs = append(batchCoordinatorL1txs, &tx)
+				batchCoordinatorL1Txs = append(batchCoordinatorL1Txs, &tx)
 				idx++
 			}
 
@@ -120,7 +122,7 @@ sig := accounts[idxTokenIDToString(inst.To, inst.TokenID)].BJJ.SignPoseidon(toSign)
 			tx.Signature = sig
 
 			accounts[idxTokenIDToString(inst.From, inst.TokenID)].Nonce++
-			batchL2txs = append(batchL2txs, &tx)
+			batchPoolL2Txs = append(batchPoolL2Txs, &tx)
 
 		case common.TxTypeExit, common.TxTypeForceExit:
 			tx := common.L1Tx{
@@ -130,22 +132,30 @@ TokenID: inst.TokenID,
 				Amount:  big.NewInt(int64(inst.Amount)),
 				Type:    common.TxTypeExit,
 			}
-			batchL1txs = append(batchL1txs, &tx)
+			batchL1Txs = append(batchL1Txs, &tx)
 		case TypeNewBatch:
-			l1txs = append(l1txs, batchL1txs)
-			coordinatorL1txs = append(coordinatorL1txs, batchCoordinatorL1txs)
-			l2txs = append(l2txs, batchL2txs)
-			batchL1txs = []*common.L1Tx{}
-			batchCoordinatorL1txs = []*common.L1Tx{}
-			batchL2txs = []*common.PoolL2Tx{}
+			l1Txs = append(l1Txs, batchL1Txs)
+			coordinatorL1Txs = append(coordinatorL1Txs, batchCoordinatorL1Txs)
+			poolL2Txs = append(poolL2Txs, batchPoolL2Txs)
+			batchL1Txs = []*common.L1Tx{}
+			batchCoordinatorL1Txs = []*common.L1Tx{}
+			batchPoolL2Txs = []*common.PoolL2Tx{}
 		default:
 			continue
 		}
 
 	}
-	l1txs = append(l1txs, batchL1txs)
-	coordinatorL1txs = append(coordinatorL1txs, batchCoordinatorL1txs)
-	l2txs = append(l2txs, batchL2txs)
+	l1Txs = append(l1Txs, batchL1Txs)
+	coordinatorL1Txs = append(coordinatorL1Txs, batchCoordinatorL1Txs)
+	poolL2Txs = append(poolL2Txs, batchPoolL2Txs)
+
+	return l1Txs, coordinatorL1Txs, poolL2Txs
+}
 
-	return l1txs, coordinatorL1txs, l2txs
+func GenerateTestTxsFromSet(t *testing.T, set string) ([][]*common.L1Tx, [][]*common.L1Tx, [][]*common.PoolL2Tx) {
+	parser := NewParser(strings.NewReader(set))
+	instructions, err := parser.Parse()
+	require.Nil(t, err)
+
+	return GenerateTestTxs(t, instructions)
 }

@@ -52,7 +52,7 @@ }
 
 // Reset tells the TxSelector to get it's internal AccountsDB
 // from the required `batchNum`
-func (txsel *TxSelector) Reset(batchNum uint64) error {
+func (txsel *TxSelector) Reset(batchNum common.BatchNum) error {
 	err := txsel.localAccountsDB.Reset(batchNum, true)
 	if err != nil {
 		return err
@@ -61,7 +61,7 @@ return nil
 }
 
 // GetL2TxSelection returns a selection of the L2Txs for the next batch, from the L2DB pool
-func (txsel *TxSelector) GetL2TxSelection(batchNum uint64) ([]*common.PoolL2Tx, error) {
+func (txsel *TxSelector) GetL2TxSelection(batchNum common.BatchNum) ([]*common.PoolL2Tx, error) {
 	// get pending l2-tx from tx-pool
 	l2TxsRaw, err := txsel.l2db.GetPendingTxs() // once l2db ready, maybe use parameter 'batchNum'
 	if err != nil {
@@ -90,7 +90,7 @@ return txs, nil
 }
 
 // GetL1L2TxSelection returns the selection of L1 + L2 txs
-func (txsel *TxSelector) GetL1L2TxSelection(batchNum uint64, l1txs []*common.L1Tx) ([]*common.L1Tx, []*common.L1Tx, []*common.PoolL2Tx, error) {
+func (txsel *TxSelector) GetL1L2TxSelection(batchNum common.BatchNum, l1txs []*common.L1Tx) ([]*common.L1Tx, []*common.L1Tx, []*common.PoolL2Tx, error) {
 	// apply l1-user-tx to localAccountDB
 	//     create new leaves
 	//     update balances
@@ -153,6 +153,9 @@ }
 
 func (txsel *TxSelector) getL2Profitable(txs txs, max uint64) txs {
 	sort.Sort(txs)
+	if len(txs) < int(max) {
+		return txs
+	}
 	return txs[:max]
 }
 func (txsel *TxSelector) createL1OperatorTxForL2Tx(accounts []*common.Account) []*common.L1Tx {