refactor(abstract-utxo): consolidate and refactor unit tests

Consolidate test fixtures and refactor unit tests for better organization.
Move address validation tests to their own file, reorganize BTC backup key
fixtures and audit tests, and consolidate spoofing protection tests.

Issue: BTC-2650

Co-authored-by: llm-git <llm-git@ttll.de>

Author: OttoAllmendinger

modules/abstract-utxo/test/unit/impl/btc/unit/fixtures/btcBackupKey.ts

@@ -1,7 +1,11 @@
 import * as assert from 'assert';
 
 import 'should';
+import { type TestBitGoAPI, TestBitGo } from '@bitgo/sdk-test';
+import { BitGoAPI } from '@bitgo/sdk-api';
+
 import { AbstractUtxoCoin } from '../../src';
+import { Tbtc } from '../../src/impl/btc';
 
 import { utxoCoins } from './util';
 
@@ -16,3 +20,54 @@ function run(coin: AbstractUtxoCoin) {
 }
 
 utxoCoins.forEach((c) => run(c));
+
+describe('Audit Key', function () {
+  // Encrypted backup key fixture for testing assertIsValidKey
+  const btcBackupKey = {
+    key:
+      '{"iv":"JgqqE4W45/tKBSMSYqD+qg==","v":1,"iter":10000,"ks":256,"ts":64,"mode"' +
+      ':"ccm","adata":"","cipher":"aes","salt":"kiLPf8VSdI0=","ct":"zUh4Oko/06g02E' +
+      'wnqOfzJbTwtE2p3b19jDk8Tum07Jv3N/RP7Bo0w/ObLBO1uIJFossO3nJ1JS+7t/vPQhdCtN8oD' +
+      '6YrZnEZYrRwN6JQkL1uYPnZ1PoWbYI9navK5CLU1KQwDTO9YEN46++OrzFH+CjpQVLblaw="}',
+  };
+
+  let bitgo: TestBitGoAPI;
+  let coin: Tbtc;
+
+  before(function () {
+    bitgo = TestBitGo.decorate(BitGoAPI, { env: 'test' });
+    bitgo.safeRegister('tbtc', Tbtc.createInstance);
+    bitgo.initializeTestVars();
+    coin = bitgo.coin('tbtc') as Tbtc;
+  });
+
+  it('should return for valid inputs', function () {
+    coin.assertIsValidKey({
+      encryptedPrv: btcBackupKey.key,
+      walletPassphrase: 'kAm[EFQ6o=SxlcLFDw%,',
+    });
+  });
+
+  it('should throw error if the walletPassphrase is incorrect', function () {
+    assert.throws(
+      () =>
+        coin.assertIsValidKey({
+          encryptedPrv: btcBackupKey.key,
+          walletPassphrase: 'foo',
+        }),
+      { message: "failed to decrypt prv: ccm: tag doesn't match" }
+    );
+  });
+
+  it('should throw if the key is altered', function () {
+    const alteredKey = btcBackupKey.key.replace(/[0-9]/g, '0');
+    assert.throws(
+      () =>
+        coin.assertIsValidKey({
+          encryptedPrv: alteredKey,
+          walletPassphrase: 'kAm[EFQ6o=SxlcLFDw%,',
+        }),
+      { message: 'failed to decrypt prv: json decrypt: invalid parameters' }
+    );
+  });
+});

modules/abstract-utxo/test/unit/impl/btc/unit/fixtures/index.ts

@@ -0,0 +1,53 @@
+import 'should';
+
+import { type TestBitGoAPI, TestBitGo } from '@bitgo/sdk-test';
+import { BitGoAPI } from '@bitgo/sdk-api';
+import { fixedScriptWallet } from '@bitgo/wasm-utxo';
+import * as testutils from '@bitgo/wasm-utxo/testutils';
+
+import { Tbtc } from '../../src/impl/btc';
+
+import { constructPsbt } from './util';
+
+const { BitGoPsbt } = fixedScriptWallet;
+
+describe('Post Build Validation', function () {
+  let bitgo: TestBitGoAPI;
+  let coin: Tbtc;
+
+  before(function () {
+    bitgo = TestBitGo.decorate(BitGoAPI, { env: 'test' });
+    bitgo.safeRegister('tbtc', Tbtc.createInstance);
+    bitgo.initializeTestVars();
+    coin = bitgo.coin('tbtc') as Tbtc;
+  });
+
+  it('should not modify locktime on postProcessPrebuild', async function () {
+    const walletKeys = testutils.getDefaultWalletKeys();
+
+    // Create a PSBT with lockTime=0 and sequence=0xffffffff
+    const psbt = constructPsbt(
+      [{ scriptType: 'p2wsh' as const, value: BigInt(100000) }],
+      [{ address: 'tb1qrp33g0q5c5txsp9arysrx4k6zdkfs4nce4xj0gdcccefvpysxf3q0sl5k7', value: BigInt(90000) }],
+      'tbtc',
+      walletKeys,
+      { lockTime: 0, sequence: 0xffffffff }
+    );
+
+    const txHex = Buffer.from(psbt.serialize()).toString('hex');
+    const blockHeight = 100;
+    const preBuild = { txHex, blockHeight };
+    const postProcessBuilt = await coin.postProcessPrebuild(preBuild);
+
+    // Parse result as PSBT
+    const resultPsbt = BitGoPsbt.fromBytes(Buffer.from(postProcessBuilt.txHex as string, 'hex'), 'tbtc');
+
+    resultPsbt.lockTime.should.equal(0);
+
+    // Check sequences via parseTransactionWithWalletKeys
+    const parsed = resultPsbt.parseTransactionWithWalletKeys(walletKeys, { publicKeys: [] });
+    for (const input of parsed.inputs) {
+      input.sequence.should.equal(0xffffffff);
+    }
+  });
+});