fix(sdk-coin-flr): set default transaction fee for export in P txn

modules/sdk-coin-flrp/src/lib/ImportInCTxBuilder.ts

@@ -126,8 +126,6 @@ export class ImportInCTxBuilder extends AtomicInCTransactionBuilder {
   protected buildFlareTransaction(): void {
     // if tx has credentials or was already recovered from raw, tx shouldn't change
     if (this.transaction.hasCredentials) return;
-    // If fee is already calculated (from initBuilder), the transaction is already built
-    if (this.transaction._fee.fee) return;
     if (this.transaction._to.length !== 1) {
       throw new Error('to is required');
     }

modules/sdk-coin-flrp/src/lib/atomicTransactionBuilder.ts

@@ -20,6 +20,7 @@ export abstract class AtomicTransactionBuilder extends TransactionBuilder {
   constructor(_coinConfig: Readonly<CoinConfig>) {
     super(_coinConfig);
     this.transaction = new Transaction(_coinConfig);
+    this.transaction._fee.fee = this.fixedFee;
   }
 
   /**

modules/sdk-coin-flrp/test/unit/lib/exportInPTxBuilder.ts

@@ -5,12 +5,54 @@ import {
   EXPORT_IN_P_TWO_UTXOS as twoUtxoTestData,
   EXPORT_IN_P_NO_CHANGE as noChangeTestData,
 } from '../../resources/transactionData/exportInP';
-import { TransactionBuilderFactory, DecodedUtxoObj } from '../../../src/lib';
-import { coins } from '@bitgo/statics';
+import { TransactionBuilderFactory, DecodedUtxoObj, Transaction } from '../../../src/lib';
+import { coins, FlareNetwork } from '@bitgo/statics';
 import signFlowTest from './signFlowTestSuit';
 
 describe('Flrp Export In P Tx Builder', () => {
-  const factory = new TransactionBuilderFactory(coins.get('tflrp'));
+  const coinConfig = coins.get('tflrp');
+  const factory = new TransactionBuilderFactory(coinConfig);
+
+  describe('default fee', () => {
+    const FIXED_FEE = (coinConfig.network as FlareNetwork).txFee;
+
+    it('should set fixedFee (1000000) by default in constructor', () => {
+      const txBuilder = factory.getExportInPBuilder();
+      // The fixedFee should be set from network.txFee = '1000000'
+      const transaction = (txBuilder as any).transaction;
+      transaction._fee.fee.should.equal(FIXED_FEE);
+    });
+
+    it('should use default fixedFee when fee is not explicitly set', async () => {
+      // Create a UTXO with enough balance to cover amount + default fee
+      const amount = '500000000'; // 0.5 FLR
+      const utxoAmount = (BigInt(amount) + BigInt(FIXED_FEE)).toString(); // amount + fixedFee
+
+      const txBuilder = factory
+        .getExportInPBuilder()
+        .threshold(testData.threshold)
+        .locktime(testData.locktime)
+        .fromPubKey(testData.pAddresses)
+        .amount(amount)
+        .externalChainId(testData.sourceChainId)
+        // NOTE: .fee() is NOT called - should use default fixedFee
+        .utxos([
+          {
+            outputID: 0,
+            amount: utxoAmount,
+            txid: '21hcD64N9QzdayPjhKLsBQBa8FyXcsJGNStBZ3vCRdCCEsLru2',
+            outputidx: '0',
+            addresses: testData.outputs[0].addresses,
+            threshold: testData.threshold,
+          },
+        ]);
+
+      const tx = (await txBuilder.build()) as Transaction;
+
+      // Verify the fee in the built transaction equals the fixedFee
+      tx.fee.fee.should.equal(FIXED_FEE);
+    });
+  });
 
   describe('validate txBuilder fields', () => {
     const txBuilder = factory.getExportInPBuilder();

modules/sdk-coin-flrp/test/unit/lib/importInPTxBuilder.ts

@@ -1,12 +1,53 @@
 import assert from 'assert';
 import 'should';
 import { IMPORT_IN_P as testData } from '../../resources/transactionData/importInP';
-import { TransactionBuilderFactory, DecodedUtxoObj } from '../../../src/lib';
-import { coins } from '@bitgo/statics';
+import { TransactionBuilderFactory, DecodedUtxoObj, Transaction } from '../../../src/lib';
+import { coins, FlareNetwork } from '@bitgo/statics';
 import signFlowTest from './signFlowTestSuit';
 
 describe('Flrp Import In P Tx Builder', () => {
-  const factory = new TransactionBuilderFactory(coins.get('tflrp'));
+  const coinConfig = coins.get('tflrp');
+  const factory = new TransactionBuilderFactory(coinConfig);
+
+  describe('default fee', () => {
+    const FIXED_FEE = (coinConfig.network as FlareNetwork).txFee;
+
+    it('should set fixedFee (1000000) by default in constructor', () => {
+      const txBuilder = factory.getImportInPBuilder();
+      // The fixedFee should be set from network.txFee = '1000000'
+      const transaction = (txBuilder as any).transaction;
+      transaction._fee.fee.should.equal(FIXED_FEE);
+    });
+
+    it('should use default fixedFee when fee is not explicitly set', async () => {
+      // Create a UTXO with enough balance to cover the default fee
+      const utxoAmount = '50000000'; // 0.05 FLR - enough to cover fee and have output
+
+      const txBuilder = factory
+        .getImportInPBuilder()
+        .threshold(testData.threshold)
+        .locktime(testData.locktime)
+        .fromPubKey(testData.pAddresses)
+        .externalChainId(testData.sourceChainId)
+        // NOTE: .fee() is NOT called - should use default fixedFee
+        .utxos([
+          {
+            outputID: 0,
+            amount: utxoAmount,
+            txid: testData.outputs[0].txid,
+            outputidx: '0',
+            addresses: testData.outputs[0].addresses,
+            threshold: testData.threshold,
+          },
+        ]);
+
+      const tx = (await txBuilder.build()) as Transaction;
+
+      // Verify the fee in the built transaction equals the fixedFee
+      tx.fee.fee.should.equal(FIXED_FEE);
+    });
+  });
+
   describe('validate txBuilder fields', () => {
     const txBuilder = factory.getImportInPBuilder();