From order to refund
Orders
Creation, transactions, processing, capture, cancellation and refunds.
- Create
- Process
- Capture
- Refund
YOUR SANDBOX. YOUR RULES.
Test payments.
Real
possibilities.
Your local lab for payment integrations. Emulate selected Mercado Pago, Stripe and PayPal flows with an API, checkout and control over every outcome.
Independent of your provider’s sandbox.
LOCAL ENVIRONMENTReady to experiment
POST → 200Illustrative view · no real money
No real credentialsNo real cardsNo real moneyRuns locally
FAMILIAR CONTRACTS
The gateways you integrate. An environment you control.
Test your integration flow using each provider’s own vocabulary.
Capture on your terms
PaymentIntents · Refunds
Create/confirm, manual capture and refunds, with Stripe-shaped errors.
- Create
- Confirm
- Capture
- Refund
Approval flow included
Orders v2 · Payments v2
Local OAuth, approval, authorization, capture, void and refunds.
- Create
- Approve
- Capture
- Refund
Selected flows, not complete catalogues. Read the fidelity reports for exact coverage and limitations.
HOW IT WORKS
Change the destination. Keep your integration.
Register an application, configure its local credentials and point your integration at the emulator. Every request follows an observable path.
Explore the architectureRequest
HTTP → Contract → Outcome- Your applicationSend the request
- Emulator APIValidate the contract
- Provider emulatorTranslate the operation
- Fake bank + ledgerRecord the movement
- WebhookNotify the outcome
- Your applicationProcess the event
One shared path. Each provider’s contract at the edges.
DETERMINISTIC SCENARIOS
That tricky edge case. One scenario away.
An approved payment, a decline or a pending action. Choose the outcome to reproduce the case you need to debug, over and over.
Same scenario. Same outcome.
Assign the scenario to your application or use X-Emulator-Scenario per request.
Design scenarioscreation scenario
Contract
payment.createWebhook enabledstripe/payment-approved.json
{
"provider": "stripe",
"version": 1,
"when": {
"operation": "payment.create"
},
"then": {
"outcome": "captured",
"webhook": {
"enabled": true,
"delayMs": 50
}
}
}Canonical outcome
capturedInteractive example · no requests are sent
Illustrative trace
trace_demoOne request. Its complete history.
- Inbound
request.received - Validation
contract.validated - Scenario
scenario.matched - Response
response.sent
Webhook delivery
Worker · signature · retries · history
WEBHOOKS + TRACES
Follow the payment. Understand the why.
Inspect which contract was validated and which scenario matched. Review webhook deliveries and retries, and connect the request to your logs through its correlation ID.
FAKE BANK. REALISTIC ACCOUNTING.
Every movement has a counterpart.
Payments are more than magic states. The fake bank records double-entry postings to track captures, fees, reserves, settlements and refunds.
Balances derived from postings. Amounts in minor units. No real money.
Meet the fake bankDifference between debits and credits0.00 USDOne currency · double entry
| Account | Debit | Credit |
|---|---|---|
| System cash | 100.00 USD | — |
| Funds in transit | — | 100.00 USD |
Debits = credits
ONE LAB, THREE SURFACES
Integrate. Simulate. Inspect.
Three separate applications, connected through the API.
Request
POST /v1/payment_intents{
"amount": 10000,
"currency": "usd",
"confirm": true
}API
For your integrationProvider contracts, scenarios and payment operations, powered by NestJS.
Contracts and APIApplicationsPayments
demo-storeStripepayment_demoCapturedConsole
For developersApplications, local credentials, payments, ledger, webhooks and traces.
Open the consoleTest card100.00 USDSimulated payment
•••• 4242Checkout
For buyersTest the buying experience with each provider’s visual identity and flow.
Explore the checkoutFROM REPOSITORY TO FIRST PAYMENT
Your next sandbox lives on your machine.
Clone the repository and run the installer. It checks Node, prepares the environment, installs, builds, migrates and creates your administrator.
Installation guideTerminal · repository root
npm run setupWhat the installer prepares
- 01Node version and environment
- 02Dependencies and build
- 03Database migrations
- 04Administrator account
Node ≥ 22.17 · Docker Compose or local PostgreSQL
Docker leaves the stack running. In local mode, start the processes using the guide.
- 01Clone
- 02Set up
- 03Run
- 04Integrate
- 05Simulate
- 06Inspect
DOCUMENTATION WITHOUT GUESSWORK
Fewer assumptions. More answers.
Spanish and English guides, from your first run to the limits of each contract.
Browse all documentationFREQUENTLY ASKED
What is worth knowing before you start.
Short answers, each with the document behind it.
Browse all documentationWhat is Payment Emulator Lab?
A local payment gateway emulator: an API, a console, a checkout and a fake bank with double-entry accounting. It runs entirely on your machine.
Project overviewDo I need real credentials or cards?
No. You register your application in the emulator and it issues the local credentials you sign each request with. No real card or account is involved.
Getting startedDoes it replace the Stripe, PayPal or Mercado Pago sandbox?
No, and it is not an official product of those providers. It emulates selected flows in their vocabulary; the fidelity reports state what is covered and what is not.
Features and limitsWhich flows are supported?
Mercado Pago with Orders; Stripe with PaymentIntents and refunds; PayPal with Orders v2 and Payments v2. Each fidelity report details the scope per provider.
Stripe reportCan I test webhooks and debug what happened?
Yes. The emulator emits an event for each operation, records its deliveries and keeps the trace of the request that produced them.
Webhooks and tracesCan I force a decline or a specific case?
Yes. Deterministic scenarios bind a condition to an outcome, so the same case reproduces identically every time you need it.
Deterministic scenariosYOUR NEXT PAYMENT IS A TEST
Stop testing payment integrations with real money and credentials.
Your code, your scenarios and an environment to understand every outcome.