I'm exploring an idea for a developer-focused SaaS: A unified UAT environment for payment gateways — essentially a sandbox simulator that lets developers integrate payments without creating multiple sandbox accounts or dealing with inconsistent/mock behaviors across gateways.

The Problem

If you’ve ever integrated payments, you know:

Stripe has excellent test tooling

Razorpay is decent

Paytm/PayU/etc vary a lot

Many banks don’t have predictable UAT behavior

Webhooks arrive differently, some delayed, some flaky

Testing disputes/refunds/settlements is nearly impossible

For dev teams building complex flows, they end up writing internal mocks, maintaining them, and still missing edge cases.

The Idea (SaaS)

A unified Payment Sandbox Simulator that:

Mock APIs for multiple gateways

Stripe

Razorpay

Paytm

PayU

Cashfree

Worldline

Visa/Mastercard tokenization mock

UPI PSP simulators

Simulate real-world scenarios

Captures

Refunds

Partial refunds

Chargebacks

Disputes

Settlement delays

Failed payouts

KYC verification

Randomized webhook delays/skips

Network downtime simulation

3-D Secure / OTP mock pages

UPI timeouts / pending states

Hosted dashboards

View mock transactions

Trigger lifecycle events (manually or timed)

Trigger webhooks again

Create custom gateway profiles

Define “rules” to simulate: failure %, latency, webhook disorder, retries

For engineering teams

Private UAT environment in one URL

No more creating 10 sandbox accounts

CI-friendly “headless payment” flows

Add Mock PG in local → swap to real PG in staging

Automatic contract testing

Pricing thought

Free Tier → 100 test transactions/mo $29/mo → small teams $99/mo → startups $499/mo → enterprise / white-label

Ask to HN

Would you use this? What’s missing? Would payments teams trust a 3rd-party simulator? Which gateways or scenarios matter most?

Happy to answer questions