test: add comprehensive test suites for batch operations atomicity, timeout/error handling, currency conversion accuracy, and webhook signature verification (#1042-#1045)

[hartz0]

What this fixes

This PR adds comprehensive test coverage for four critical SDK core systems:

1. Test batch operations atomicity #1045 - Test batch operations atomicity: There was missing dedicated test coverage verifying that batch operations guarantee atomicity across successful transactions, partial failures, rollback coordination, and consistency invariants.
2. Test timeout and error handling #1044 - Test timeout and error handling: There was missing comprehensive test coverage for request timeout enforcement, per-method overrides, network error classification/recovery with exponential backoff, XDR/JSON parse errors, and input validation with recovery.
3. Test currency conversion accuracy #1043 - Test currency conversion accuracy: There was missing test validation for oracle price conversion accuracy (fixed-point 18-decimal scaling), multi-asset precision preservation across custom decimals, largest-remainder split rounding calculations, and numerical edge cases.
4. Test webhook signature verification #1042 - Test webhook signature verification: There was missing end-to-end test verification for HMAC-SHA256 signature verification, rejection of tampered/mismatched payloads, timestamp tolerance replay protection, and LRU nonce tracking deduplication.

What changed

• Batch Operations Atomicity (Test batch operations atomicity #1045):

  • Added dedicated test suite test/batchOperationsAtomicity.test.ts (13 tests) covering:
    • Multi-leg split payment coordination when all legs succeed.
    • Concurrency-limited invoice batch processing via InvoiceBatchProcessor.
    • Partial failure isolation where failed legs are identified without aborting remaining operations.
    • Rollback snapshot initiation with RollbackCoordinator emitting splitRollbackInitiated and splitRollbackCompleted events.
    • Rollback timeout cleanup ensuring no orphaned state remains on execution timeout.
    • LIFO rollback order and idempotent rollback in OptimisticCache.
    • Exact split amount balance conservation (zero stroops created or lost).
  • Initialized eventHandlers and expiries in OptimisticCache (src/cache/OptimisticCache.ts) to ensure clean cache lifecycle event dispatch during rollback.

• Timeout and Error Handling (Test timeout and error handling #1044):

  • Added dedicated test suite test/timeoutAndErrorHandling.test.ts (17 tests) covering:
    • withTimeout and withTimeoutOrThrow triggering RequestTimeoutError with method context and cancellation via AbortSignal.
    • TimeoutManager per-method timeout overrides and default fallback configuration.
    • Pre-deadline escalation warning dispatch via EscalationManager.
    • Error classification with isRetryable (transient 503, 429, ECONNREFUSED vs non-retryable 400, 404, InvoiceNotFoundError).
    • Transient network failure retry recovery via executeWithRetry.
    • Secondary RPC recovery via FallbackChain.
    • Malformed base64 XDR envelope parse failure handling via parseEnvelope.
    • JSON and hex decoding validation with descriptive error context.
    • Parameter validation recovery on ValidationError.

• Currency Conversion Accuracy (Test currency conversion accuracy #1043):

  • Added dedicated test suite test/currencyConversionAccuracy.test.ts (19 tests) covering:
    • Accurate 18-decimal fixed-point oracle rate conversions (rate > 1.0, fractional rate < 1.0, and 1:1 parity).
    • convertFiatToAsset fiat-to-token conversions and rejection of non-positive exchange rates with OraclePriceError.
    • Lossless 7-decimal XLM stroop precision in normalizeAmount and toOnChainAmount.
    • Custom token precisions (6 decimals for USDC, 2 for fiat, 0 for integer units).
    • Rejection of fractional values exceeding asset precision with PrecisionError.
    • Hamilton-Hare largest-remainder method in auditSplitRounding ensuring exact sum preservation.
    • Detection of invalid ratio divergence via RoundingOverflowError.
    • Extreme numerical edge cases: 0 amounts, 1 stroop, and 100-billion-token BigInts.

• Webhook Signature Verification (Test webhook signature verification #1042):

  • Added dedicated test suite test/webhookSignatureVerification.test.ts (22 tests) covering:
    • Valid HMAC-SHA256 signature computation and verification across string and Buffer bodies.
    • Signature prefix handling (sha256= and hmac-sha256=).
    • Event emission on verification (webhook.validated and webhook.rejected).
    • Raw verification via webhooks/verify.ts and webhookValidator.ts.
    • Constant-time comparison via safeCompare preventing timing attacks.
    • Rejection of mismatched secrets, tampered bodies, tampered signature bytes, and malformed hex.
    • Replay protection with timestamp tolerance windows and clock skew tolerance.
    • Replay attack detection via nonce tracking and deduplication.
    • LRU capacity eviction and retrieval in RingBufferStore for webhook replay.

Testing

Ran all newly created and default test suites using Vitest:

• test/batchOperationsAtomicity.test.ts (13 passed)
• test/timeoutAndErrorHandling.test.ts (17 passed)
• test/currencyConversionAccuracy.test.ts (19 passed)
• test/webhookSignatureVerification.test.ts (22 passed)
• npm test (test/client.test.ts, test/retryPolicy.test.ts, test/network-environment.test.ts) (110 passed)
  Total: 7 test files, 181 tests passed, 0 failures.

Issues

closes #1045
closes #1044
closes #1043
closes #1042

[drips-wave]

@hartz0 Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits