diff --git a/src/contract/test-harness/src/dao_exec.rs b/src/contract/test-harness/src/dao_exec.rs
index 4ecb3f97a..9eae646ce 100644
--- a/src/contract/test-harness/src/dao_exec.rs
+++ b/src/contract/test-harness/src/dao_exec.rs
@@ -18,7 +18,10 @@
 
 use std::time::Instant;
 
-use darkfi::{tx::Transaction, Result};
+use darkfi::{
+    tx::{ContractCallLeaf, Transaction, TransactionBuilder},
+    Result,
+};
 use darkfi_dao_contract::{
     client::DaoExecCall,
     model::{Dao, DaoBulla, DaoExecParams, DaoProposal},
@@ -161,11 +164,13 @@ impl TestHarness {
         exec_params.encode(&mut data)?;
         let exec_call = ContractCall { contract_id: *DAO_CONTRACT_ID, data };
 
-        let mut tx = Transaction {
-            calls: vec![xfer_call, exec_call],
-            proofs: vec![xfer_secrets.proofs, exec_proofs],
-            signatures: vec![],
-        };
+        let mut tx_builder = TransactionBuilder::new(
+            ContractCallLeaf { call: exec_call, proofs: exec_proofs },
+            vec![],
+        );
+        tx_builder
+            .append(ContractCallLeaf { call: xfer_call, proofs: xfer_secrets.proofs }, vec![])?;
+        let mut tx = tx_builder.build()?;
         let xfer_sigs = tx.create_sigs(&mut OsRng, &xfer_secrets.signature_secrets)?;
         let exec_sigs = tx.create_sigs(&mut OsRng, &[exec_signature_secret])?;
         tx.signatures = vec![xfer_sigs, exec_sigs];
diff --git a/src/contract/test-harness/src/dao_mint.rs b/src/contract/test-harness/src/dao_mint.rs
index 361289d1e..a29f6124a 100644
--- a/src/contract/test-harness/src/dao_mint.rs
+++ b/src/contract/test-harness/src/dao_mint.rs
@@ -18,7 +18,10 @@
 
 use std::time::Instant;
 
-use darkfi::{tx::Transaction, Result};
+use darkfi::{
+    tx::{ContractCallLeaf, Transaction, TransactionBuilder},
+    Result,
+};
 use darkfi_dao_contract::{
     client,
     model::{Dao, DaoMintParams},
@@ -50,9 +53,9 @@ impl TestHarness {
 
         let mut data = vec![DaoFunction::Mint as u8];
         params.encode(&mut data)?;
-        let calls = vec![ContractCall { contract_id: *DAO_CONTRACT_ID, data }];
-        let proofs = vec![proofs];
-        let mut tx = Transaction { calls, proofs, signatures: vec![] };
+        let call = ContractCall { contract_id: *DAO_CONTRACT_ID, data };
+        let mut tx_builder = TransactionBuilder::new(ContractCallLeaf { call, proofs }, vec![]);
+        let mut tx = tx_builder.build()?;
         let sigs = tx.create_sigs(&mut OsRng, &[dao_kp.secret])?;
         tx.signatures = vec![sigs];
         tx_action_benchmark.creation_times.push(timer.elapsed());
diff --git a/src/contract/test-harness/src/dao_propose.rs b/src/contract/test-harness/src/dao_propose.rs
index b4a354f6d..81587a7a1 100644
--- a/src/contract/test-harness/src/dao_propose.rs
+++ b/src/contract/test-harness/src/dao_propose.rs
@@ -18,7 +18,10 @@
 
 use std::time::Instant;
 
-use darkfi::{tx::Transaction, Result};
+use darkfi::{
+    tx::{ContractCallLeaf, Transaction, TransactionBuilder},
+    Result,
+};
 use darkfi_dao_contract::{
     client::{DaoProposeCall, DaoProposeStakeInput},
     model::{Dao, DaoBulla, DaoProposal, DaoProposeParams},
@@ -110,9 +113,9 @@ impl TestHarness {
 
         let mut data = vec![DaoFunction::Propose as u8];
         params.encode(&mut data)?;
-        let calls = vec![ContractCall { contract_id: *DAO_CONTRACT_ID, data }];
-        let proofs = vec![proofs];
-        let mut tx = Transaction { calls, proofs, signatures: vec![] };
+        let call = ContractCall { contract_id: *DAO_CONTRACT_ID, data };
+        let mut tx_builder = TransactionBuilder::new(ContractCallLeaf { call, proofs }, vec![]);
+        let mut tx = tx_builder.build()?;
         let sigs = tx.create_sigs(&mut OsRng, &[signature_secret])?;
         tx.signatures = vec![sigs];
         tx_action_benchmark.creation_times.push(timer.elapsed());
diff --git a/src/contract/test-harness/src/dao_vote.rs b/src/contract/test-harness/src/dao_vote.rs
index be35cdf15..f2e2b5fef 100644
--- a/src/contract/test-harness/src/dao_vote.rs
+++ b/src/contract/test-harness/src/dao_vote.rs
@@ -18,7 +18,10 @@
 
 use std::time::Instant;
 
-use darkfi::{tx::Transaction, Result};
+use darkfi::{
+    tx::{ContractCallLeaf, Transaction, TransactionBuilder},
+    Result,
+};
 use darkfi_dao_contract::{
     client::{DaoVoteCall, DaoVoteInput},
     model::{Dao, DaoProposal, DaoProposalBulla, DaoVoteParams},
@@ -93,9 +96,9 @@ impl TestHarness {
 
         let mut data = vec![DaoFunction::Vote as u8];
         params.encode(&mut data)?;
-        let calls = vec![ContractCall { contract_id: *DAO_CONTRACT_ID, data }];
-        let proofs = vec![proofs];
-        let mut tx = Transaction { calls, proofs, signatures: vec![] };
+        let call = ContractCall { contract_id: *DAO_CONTRACT_ID, data };
+        let mut tx_builder = TransactionBuilder::new(ContractCallLeaf { call, proofs }, vec![]);
+        let mut tx = tx_builder.build()?;
         let sigs = tx.create_sigs(&mut OsRng, &[signature_secret])?;
         tx.signatures = vec![sigs];
         tx_action_benchmark.creation_times.push(timer.elapsed());