diff --git a/miner/builder.go b/miner/builder.go
index 4e9fe4ec68..1c4a08b9e2 100644
--- a/miner/builder.go
+++ b/miner/builder.go
@@ -64,6 +64,7 @@ func NewBuilder(config *BuilderConfig, args *BuilderArgs) (*Builder, error) {
 		chainConfig: config.ChainConfig,
 		engine:      config.Engine,
 		chain:       config.Chain,
+		txpool:      config.EthBackend.TxPool(),
 	}
 
 	workerParams := &generateParams{
diff --git a/miner/builder_test.go b/miner/builder_test.go
index a538086236..3db8b8e47b 100644
--- a/miner/builder_test.go
+++ b/miner/builder_test.go
@@ -34,7 +34,7 @@ func TestBuilder_AddTxn_Simple(t *testing.T) {
 	require.NoError(t, err)
 	require.True(t, res.Success)
 	require.Len(t, builder.env.receipts, 1)
-	require.Equal(t, big.NewInt(1000), builder.env.state.GetBalance(testUserAddress))
+	require.Equal(t, big.NewInt(1000), builder.env.state.GetBalance(testUserAddress).ToBig())
 
 	// we cannot add the same transaction again. Note that by design the
 	// function does not error but returns the SimulateTransactionResult.success = false
@@ -42,7 +42,7 @@ func TestBuilder_AddTxn_Simple(t *testing.T) {
 	require.NoError(t, err)
 	require.False(t, res.Success)
 	require.Len(t, builder.env.receipts, 1)
-	require.Equal(t, big.NewInt(1000), builder.env.state.GetBalance(testUserAddress))
+	require.Equal(t, big.NewInt(1000), builder.env.state.GetBalance(testUserAddress).ToBig())
 }
 
 func TestBuilder_AddTxns_Simple(t *testing.T) {
@@ -60,7 +60,7 @@ func TestBuilder_AddTxns_Simple(t *testing.T) {
 	for _, r := range res {
 		require.True(t, r.Success)
 	}
-	require.Equal(t, big.NewInt(2000), builder.env.state.GetBalance(testUserAddress))
+	require.Equal(t, big.NewInt(2000), builder.env.state.GetBalance(testUserAddress).ToBig())
 
 	tx3 := backend.newRandomTxWithNonce(2)
 	tx4 := backend.newRandomTxWithNonce(1000) // fails with nonce too high
@@ -71,7 +71,7 @@ func TestBuilder_AddTxns_Simple(t *testing.T) {
 	require.True(t, res[0].Success)
 	require.False(t, res[1].Success)
 	require.Len(t, builder.env.txs, 2)
-	require.Equal(t, big.NewInt(2000), builder.env.state.GetBalance(testUserAddress))
+	require.Equal(t, big.NewInt(2000), builder.env.state.GetBalance(testUserAddress).ToBig())
 }
 
 func TestBuilder_AddBundles_Simple(t *testing.T) {
@@ -99,7 +99,7 @@ func TestBuilder_AddBundles_Simple(t *testing.T) {
 	require.Len(t, res, 2)
 	require.True(t, res[0].Success)
 	require.True(t, res[1].Success)
-	require.Equal(t, big.NewInt(4000), builder.env.state.GetBalance(testUserAddress))
+	require.Equal(t, big.NewInt(4000), builder.env.state.GetBalance(testUserAddress).ToBig())
 }
 
 func TestBuilder_AddBundles_RevertHashes(t *testing.T) {
@@ -122,7 +122,7 @@ func TestBuilder_AddBundles_RevertHashes(t *testing.T) {
 	require.Len(t, res[0].SimulateTransactionResults, 2)
 	require.True(t, res[0].SimulateTransactionResults[0].Success)
 	require.False(t, res[0].SimulateTransactionResults[1].Success)
-	require.Equal(t, big.NewInt(0), builder.env.state.GetBalance(testUserAddress))
+	require.True(t, builder.env.state.GetBalance(testUserAddress).IsZero())
 
 	bundle.RevertingHashes = []common.Hash{tx2.Hash()}
 
@@ -133,7 +133,7 @@ func TestBuilder_AddBundles_RevertHashes(t *testing.T) {
 	require.Len(t, res[0].SimulateTransactionResults, 2)
 	require.True(t, res[0].SimulateTransactionResults[0].Success)
 	require.False(t, res[0].SimulateTransactionResults[1].Success)
-	require.Equal(t, big.NewInt(1000), builder.env.state.GetBalance(testUserAddress))
+	require.Equal(t, big.NewInt(1000), builder.env.state.GetBalance(testUserAddress).ToBig())
 }
 
 func TestBuilder_AddBundles_InvalidParams(t *testing.T) {
@@ -160,7 +160,7 @@ func TestBuilder_AddBundles_InvalidParams(t *testing.T) {
 	require.False(t, res[0].Success)
 	require.Equal(t, ErrInvalidBlockNumber.Error(), res[0].Error)
 	require.Len(t, res[0].SimulateTransactionResults, 0)
-	require.Equal(t, big.NewInt(0), builder.env.state.GetBalance(testUserAddress))
+	require.True(t, builder.env.state.GetBalance(testUserAddress).IsZero())
 
 	bundle = &suavextypes.Bundle{
 		Txs:         []*types.Transaction{tx1, tx2},
@@ -174,7 +174,7 @@ func TestBuilder_AddBundles_InvalidParams(t *testing.T) {
 	require.False(t, res[0].Success)
 	require.Equal(t, ErrExceedsMaxBlock.Error(), res[0].Error)
 	require.Len(t, res[0].SimulateTransactionResults, 0)
-	require.Equal(t, big.NewInt(0), builder.env.state.GetBalance(testUserAddress))
+	require.True(t, builder.env.state.GetBalance(testUserAddress).IsZero())
 
 	bundle = &suavextypes.Bundle{
 		Txs: []*types.Transaction{},
@@ -185,7 +185,7 @@ func TestBuilder_AddBundles_InvalidParams(t *testing.T) {
 	require.False(t, res[0].Success)
 	require.Equal(t, ErrEmptyTxs.Error(), res[0].Error)
 	require.Len(t, res[0].SimulateTransactionResults, 0)
-	require.Equal(t, big.NewInt(0), builder.env.state.GetBalance(testUserAddress))
+	require.True(t, builder.env.state.GetBalance(testUserAddress).IsZero())
 }
 
 func TestBuilder_FillTransactions(t *testing.T) {
@@ -299,12 +299,11 @@ func newMockBuilderConfig(t *testing.T) (*BuilderConfig, *testWorkerBackend) {
 	engine := clique.New(config.Clique, db)
 
 	w, backend := newTestWorker(t, &config, engine, db, 0)
-	w.close()
 
 	bConfig := &BuilderConfig{
 		ChainConfig: w.chainConfig,
 		Engine:      w.engine,
-		EthBackend:  w.eth,
+		EthBackend:  backend,
 		Chain:       w.chain,
 		GasCeil:     10000000,
 	}
diff --git a/miner/payload_building_test.go b/miner/payload_building_test.go
index 1728b9e5bd..c627be5dee 100644
--- a/miner/payload_building_test.go
+++ b/miner/payload_building_test.go
@@ -110,6 +110,12 @@ func newTestWorkerBackend(t *testing.T, chainConfig *params.ChainConfig, engine
 		Config: chainConfig,
 		Alloc:  types.GenesisAlloc{testBankAddress: {Balance: testBankFunds}},
 	}
+
+	// == SUAVE SPECIFIC ==
+	// Add custom contracts for the genesis
+	gspec.Alloc[suaveExample1Addr] = core.GenesisAccount{Balance: big.NewInt(0), Code: common.FromHex(suaveExample1Artifact.DeployedBytecode.Object)}
+	// == END OF SUAVE SPECIFIC ==
+
 	switch e := engine.(type) {
 	case *clique.Clique:
 		gspec.ExtraData = make([]byte, 32+common.AddressLength+crypto.SignatureLength)
@@ -273,3 +279,25 @@ func TestPayloadId(t *testing.T) {
 		ids[id] = i
 	}
 }
+
+// --- SUAVE SPECIFIC UTILITIES ---
+
+const (
+	// testCode is the testing contract binary code which will initialises some
+	// variables in constructor
+	testCode = "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"
+
+	// testGas is the gas required for contract deployment.
+	testGas = 144109
+)
+
+func (b *testWorkerBackend) newRandomTx(creation bool) *types.Transaction {
+	var tx *types.Transaction
+	gasPrice := big.NewInt(10 * params.InitialBaseFee)
+	if creation {
+		tx, _ = types.SignTx(types.NewContractCreation(b.txPool.Nonce(testBankAddress), big.NewInt(0), testGas, gasPrice, common.FromHex(testCode)), types.HomesteadSigner{}, testBankKey)
+	} else {
+		tx, _ = types.SignTx(types.NewTransaction(b.txPool.Nonce(testBankAddress), testUserAddress, big.NewInt(1000), params.TxGas, gasPrice, nil), types.HomesteadSigner{}, testBankKey)
+	}
+	return tx
+}
diff --git a/suave/builder/session_manager.go b/suave/builder/session_manager.go
index ffdf428fac..7795c1547a 100644
--- a/suave/builder/session_manager.go
+++ b/suave/builder/session_manager.go
@@ -137,7 +137,7 @@ func (s *SessionManager) NewSession(ctx context.Context, args *api.BuildBlockArg
 }
 
 func (s *SessionManager) getSession(sessionId string, allowOnTheFlySession bool) (*miner.Builder, error) {
-	if sessionId == "" {
+	if sessionId == "" && allowOnTheFlySession {
 		return s.newBuilder(&api.BuildBlockArgs{})
 	}
 
diff --git a/suave/builder/session_manager_test.go b/suave/builder/session_manager_test.go
index 1bf6053d03..fd69268b91 100644
--- a/suave/builder/session_manager_test.go
+++ b/suave/builder/session_manager_test.go
@@ -142,7 +142,8 @@ type testBackend struct {
 
 func (tb *testBackend) newTransfer(t *testing.T, to common.Address, amount *big.Int) *types.Transaction {
 	gasPrice := big.NewInt(10 * params.InitialBaseFee)
-	tx, _ := types.SignTx(types.NewTransaction(tb.pool.Nonce(testBankAddress), to, amount, params.TxGas, gasPrice, nil), types.HomesteadSigner{}, testBankKey)
+	tx, err := types.SignTx(types.NewTransaction(tb.pool.Nonce(testBankAddress), to, amount, params.TxGas, gasPrice, nil), types.HomesteadSigner{}, testBankKey)
+	require.NoError(t, err)
 	return tx
 }