[MEDIUM] Onchain adapter mock does not simulate comprehensive failure modes

[kilodesodiq-arch]

Engineering Gap

app/backend/src/onchain/onchain.adapter.mock.ts provides a mock adapter for testing, but likely only returns success responses. Production failure modes (RPC timeout, transaction failure, simulation error, network mismatch, insufficient funds) not simulated.

Codebase Evidence

• app/backend/src/onchain/onchain.adapter.mock.ts: Mock adapter implementation
• app/backend/src/onchain/onchain.adapter.mock.spec.ts: Mock adapter tests
• app/backend/test/comprehensive-harness.e2e-spec.ts line 21: process.env.ONCHAIN_ADAPTER = mock

Risk Profile

Onchain error handling paths untested. Production failures unhandled.

Remediation Strategy

Add failure mode simulation to mock: configurable error rates, transaction timeouts, RPC errors. Test error recovery paths.

Success Conditions

• Mock supports configurable failure modes
• Error recovery tests added

Change Surface

Files: onchain.adapter.mock.ts, onchain.adapter.mock.spec.ts

Security Review

Improves error handling test coverage.

Completion Checklist

• Implementation completed
• Peer reviewed
• Tests passing
• Ready for merge

[YfengJ]

Hi maintainers, I would like to apply for this issue if it is available. If assigned, I will extend the mock onchain adapter with explicit configurable failure modes such as RPC timeout, transaction failure, simulation error, network mismatch, and insufficient funds, then add targeted tests for the mock behavior and any existing recovery paths it enables.