Throw on an attempt to submit the same transaction twice

Author: mainnet-pat

packages/cashscript/src/network/MockNetworkProvider.ts

@@ -45,6 +45,11 @@ export default class MockNetworkProvider implements NetworkProvider {
     const transactionBin = hexToBin(txHex);
 
     const txid = binToHex(sha256(sha256(transactionBin)).reverse());
+
+    if (this.transactionMap[txid]) {
+      throw new Error(`Transaction with txid ${txid} was already submitted: txn-mempool-conflict`);
+    }
+
     this.transactionMap[txid] = txHex;
 
     const decoded = decodeTransaction(transactionBin);

packages/cashscript/test/e2e/network/MockNetworkProvider.test.ts

@@ -43,17 +43,21 @@ describe('Transaction Builder', () => {
     const sigTemplate = new SignatureTemplate(alicePriv);
 
     // spend both utxos to bob
-    new TransactionBuilder({provider})
+    const builder = new TransactionBuilder({provider})
       .addInput(p2pkhUtxos[0], p2pkhInstance.unlock.spend(alicePub, sigTemplate))
       .addInput(aliceUtxos[0], sigTemplate.unlockP2PKH())
-      .addOutput({ to: bobAddress, amount: 1000n })
-      .send();
+      .addOutput({ to: bobAddress, amount: 1000n });
+
+    const tx = builder.build();
+    await builder.send();
 
     // utxos should be removed from the provider
     expect(await provider.getUtxos(aliceAddress)).toHaveLength(0);
     expect(await provider.getUtxos(p2pkhInstance.address)).toHaveLength(0);
 
     // utxo should be added to bob
     expect(await provider.getUtxos(bobAddress)).toHaveLength(1);
+
+    await expect(provider.sendRawTransaction(tx)).rejects.toThrow('txn-mempool-conflict');
   });
 });