tldr: Testsigma supports codeless REST API testing with functional validation, JSON schema-based contract testing, and consumer-driven contract testing (CDCT). API tests run alongside web and mobile tests in the same suite. No separate tools needed. The NLP approach means non-developers can write API tests too.
Introduction
Most teams treat API testing as a separate discipline. Postman for manual exploration. REST Assured for automated checks. Custom scripts for contract validation. That's three tools before you even get to UI testing.
Testsigma bakes API testing into the same codeless platform used for web and mobile testing. Same NLP interface, same test suites, same execution pipeline. You can call an API to create test data, then validate the UI displays it correctly, all in one test case.
Neither BrowserStack nor LambdaTest offers native API testing. If your evaluation criteria include API coverage, that's a point for Testsigma.
What you can do
Functional API testing
Test REST endpoints using plain English steps. No code. Support for GET, POST, PUT, PATCH, and DELETE. You set headers, query parameters, and request bodies through the NLP interface. Assertions cover status codes, headers, field values, data types, and response structure.
The practical value: you can chain API calls. POST to create a resource, GET to retrieve it, assert the data matches. Multi-step workflows that normally require REST Assured or custom code work through the same codeless interface.
Contract testing
Contract testing validates that an API's response matches an agreed-upon schema. Testsigma uses JSON Schema validation for this. Define the expected schema, run the test, and if any field is missing, extra, or mistyped, the test fails.
This catches breaking changes early. When the backend team changes a response field from string to integer, you find out in CI, not when a customer reports it.
Consumer-driven contract testing (CDCT)
The consumer (your frontend or another service) defines what it expects from an API. Tests validate that the provider meets those expectations. For microservices architectures where services depend on each other, this is how you catch integration issues before they cascade.
Testsigma handles this natively. With other approaches, you'd typically need a framework like Pact.
Mixing API and UI tests
This is the real selling point for Testsigma's API testing. You're not running API tests in isolation. They live in the same suite as your web and mobile tests.
Common pattern: use API calls to set up test data, run UI tests to validate the frontend, then use API calls to clean up. This makes UI tests faster and more reliable since you're not clicking through setup flows every time.
Another pattern: run backend regression (API tests) and frontend regression (UI tests) in the same CI pipeline, managed in the same tool. One dashboard, one set of results.
API testing comparison
| Capability | Testsigma | Postman | REST Assured |
|---|---|---|---|
| Approach | Codeless (NLP) | Low-code GUI | Code (Java) |
| Contract testing | JSON Schema + CDCT | JSON Schema | Custom assertions |
| UI + API in one tool | Yes | No | No |
| CI/CD integration | Built-in | Newman CLI | Maven/Gradle |
| Parallel execution | Built-in | Collection runner | Custom setup |
| Cost | Included in platform | Free (basic), paid (enterprise) | Free (open source) |
Postman is still the go-to for API exploration and manual testing. REST Assured is preferred by Java teams who want full code control. Testsigma's angle is unifying API tests with the rest of your test suite in a codeless environment.
Where it falls short
REST only. As of 2026, no GraphQL or gRPC support. If your stack relies on either, you'll still need separate tools.
No load testing. Testsigma validates correctness, not performance. For load and stress testing, use k6, JMeter, or Gatling.
Advanced auth flows. Complex OAuth 2.0 with token refresh or WebSocket testing may require workarounds or custom steps.
FAQs
Can non-developers actually write API tests? Yes. The NLP interface handles endpoint configuration, assertions, and data passing. It's the same plain English approach used for web and mobile tests.
Can I do contract testing without Pact? Yes. Testsigma's JSON Schema validation handles contract testing natively. No external frameworks needed.
Can API and UI tests share data? Yes. Data passes between API and UI steps within the same test case. Create data via API, validate via UI, clean up via API.
Is GraphQL supported? Not natively as of 2026. REST API testing only.
Is API testing included in all plans? Yes. Available in Pro, Enterprise, and the open-source Community Edition.
Conclusion
Testsigma's API testing isn't the deepest API tool on the market. Postman does more for exploration. REST Assured gives you more control. But Testsigma is the only codeless platform that lets you mix API, web, and mobile tests in the same suite with no code. For teams that want unified coverage and codeless API validation, it does the job. For GraphQL, WebSocket, or load testing, you'll need additional tools. See Testsigma features and Testsigma integrations for the broader platform picture.