A Practical Guide to Testing Fintech APIs End-to-End (Without Writing Extra Code)

Source: Dev.to

Introduction

Fintech APIs are tricky; payments, KYC, wallets, ledgers, refunds, transaction verification…everything needs to work perfectly. Even the smallest bug can break a customer payment or cause a compliance issue. This is why proper API testing matters more in fintech than anywhere else.

In this guide, you’ll learn how to test your fintech APIs on KushoAI: upload your API, set up environments, handle auth, run tests, and build complete end‑to‑end payment flows.

Fintech’s Typical API Workflow

Fintech systems rely on tightly connected API chains. A single customer action (e.g., onboarding or making a payment) triggers multiple backend services that interact in sequence.

• Customer Onboarding: Capture user details, trigger the KYC process, receive verification callbacks.
• KYC/AML Checks: Connect with external verification providers and government systems.
• Risk & Credit Scoring: Pull customer information, run risk engines, generate score decisions.
• Payment Authorization: Validate tokens, initiate transactions, confirm status with payment gateways.
• Ledger & Reconciliation: Update balances, record entries, match settlements across internal and partner systems.

Why Testing Fintech APIs Is Hard

Fintech systems move money, store identity data, and depend on third‑party infrastructure, which introduces several unique complexities:

• Multi‑Vendor Integrations: Banks, KYC vendors, payment gateways, and loan‑servicing partners each have different response formats, SLAs, and failure modes.
• Regulated Test Data: Compliance rules restrict the use of production‑like customer data (KYC data, PAN/Aadhaar, banking details), making realistic test cases harder to create.
• Versioned APIs: Banking and payment APIs evolve frequently; even small contract changes can break critical workflows.
• High Reliability Requirements: API failures directly impact money movement, compliance, customer trust, and operational losses.

How Fintech Teams Can Test Their APIs Using KushoAI – Prerequisites

• Your fintech APIs (Postman collection, URL, OpenAPI spec, or cURL).
• A free KushoAI account (no credit card required).

Step 1: Upload Your APIs

Upload your APIs to KushoAI and provide the necessary fields (request body, query params, etc.). After filling in the required information, click Generate to create the API tests.

Step 2: Review and Run Your Generated Tests

After clicking Generate, you’ll be redirected to the Test Suite page, which lists all generated tests. Use the Run button next to each test name to execute it. Click the details dropdown to inspect the request body.

Step 3: Generate Assertions

1. Click the Assertions button for a test and select Generate using AI.
2. Edit the generated assertions if needed, then click Save and Run.

To generate assertions for all tests, click Generate Assertions beneath the search tab. Run all tests first (or use Run All Tests) so KushoAI can create bulk assertions automatically.

Step 4: Security Testing

KushoAI’s Security Testing proactively identifies vulnerabilities by simulating real‑world attack scenarios (SQL injection, XSS, insecure authentication, etc.).

1. Click the Security button.
2. Choose Generate Security Tests.

Run the generated security tests just like functional tests and add assertions as needed.

Step 5: End‑to‑End Testing

Create a workflow that connects multiple APIs, allowing the output of one API to serve as input for the next. This enables thorough integration testing of complex, sequential scenarios.

1. In the left panel, select E2E test suite.
2. Click Create to start a new End‑to‑End test suite.