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Free API testing tools
Tools that work from the OpenAPI spec you already have. The spec tools run entirely in your browser, so nothing is uploaded.
Tools and research
API Test Case Generator
Paste an OpenAPI or Swagger spec and get positive, negative, boundary, auth, 404, pagination and response-schema test cases for every operation. Download as CSV or JSON.
Generate test cases →Free tool · In your browserOpenAPI Test-Readiness Scorer
Score how test-ready your spec is: missing error responses, security requirements and request schemas, endpoint by endpoint.
Score my spec →Free calculatorAPI Testing ROI Calculator
Estimate the time and cost of your current API testing against an automated, spec-driven approach, using your own team numbers.
Calculate ROI →Research reportState of Public OpenAPI Specs 2026
We scored 2,518 public OpenAPI specs with the test-readiness methodology. See how common missing error responses and security requirements are.
Read the report →Downloadable packs
Checklists, templates and playbooks, sent to your inbox. See all of them on the resources page.
- PDF (10 pages)
Shift Left Testing Playbook
A step-by-step guide to reducing production bugs and accelerating CI/CD pipelines
- 1-page checklist
API Testing Checklist for CI/CD Pipelines
25-point checklist to ensure your APIs are fully tested before every deployment
- PDF + code examples
OpenAPI to Test Generation Template Pack
Sample specs, generated tests, and best practices for spec-driven testing
- Visual blueprint + guide
Microservices Testing Strategy Blueprint
Architecture-driven testing strategy for distributed systems
- YAML templates + guide
CI/CD Testing Pipeline Templates
Copy-paste GitHub Actions and GitLab CI templates for API testing
- PDF guide (12 pages)
Top 50 API Testing Mistakes
Real-world mistakes with actionable fix strategies for every one
- Interactive spreadsheet + guide
Test Automation ROI Calculator
Calculate the business value of shifting testing left
- PDF + code examples
Contract Testing Starter Kit
Everything you need to start contract testing with Pact and CI/CD
- Self-assessment scorecard
API Test Coverage Scorecard
Score your API testing maturity across 8 dimensions
- Guided worksheet
Build Your Testing Strategy in 30 Minutes
A guided framework to define your testing architecture, tools, and layers
- ZIP: 5 CSV packs + guide
API Test Case Library
Five CSV packs of reusable API test cases: login, pagination, search and filtering, auth (API key, JWT, OAuth 2.0) and error handling
- ZIP: scorecard CSV + RFP CSV + guide
API Testing Tool Evaluation Scorecard & RFP Template
Weighted criteria and RFP questions for comparing Postman, ReadyAPI, Tosca, Parasoft SOAtest and AI-native tools on your own APIs
- ZIP: guide + approval checklist CSV
AI-Policy-Safe API Testing: Self-Hosted LLM Evaluation Kit
Data flows, model hosting options (Ollama, vLLM, LM Studio) and an approval checklist for security and AI governance teams
- ZIP: CSV pack + guide
OWASP API Top 10 Test-Case Pack
Positive and negative API test cases for every OWASP API Security Top 10 (2023) risk, ready to adapt to your endpoints
- ZIP: checklist + 5 CSV packs + guide
Self-Hosted & Air-Gapped API Testing: Deployment and Audit Checklist
40 deployment and audit checks for self-hosted, on-premises and disconnected API testing, plus four industry test-case packs
- ZIP: CSV pack + checklist + guide
Banking API Test-Case Pack
Payments idempotency, open banking consent, strong customer authentication, accounts, cards and ISO 20022 messaging
- ZIP: CSV pack + checklist + guide
Insurance API Test-Case Pack
Quote and rate, policy issuance and endorsements, claims first notice of loss, claim payments and broker access
- ZIP: CSV pack + checklist + guide
Healthcare API Test-Case Pack
FHIR R4 resources and search, SMART on FHIR scopes, consent, eligibility and benefits, claims and HL7 v2 messaging
- ZIP: CSV pack + checklist + guide
Public Sector API Test-Case Pack
Citizen identity and assurance levels, case management, eligibility rules, records requests and inter-agency data sharing
From test cases to a running suite
Shift-Left API turns the same spec into executable tests with assertions, without needing an AI key. 15-day trial, no credit card.