// api testing services
API Testing Services
QACraft's API testing services validate functionality, contracts, error handling and data integrity across REST, SOAP and GraphQL APIs — so your endpoints return reliable, accurate, correctly-shaped responses every time.
what it is
What Is API Testing?
API testing is the practice of verifying your application’s APIs directly at the interface — confirming that each endpoint returns the correct status codes and data, matches its agreed contract and schema, handles authentication and errors properly, and keeps your data accurate. Because it tests the service layer beneath the UI, it catches correctness defects earlier, faster and more precisely than testing through a screen ever could.
QACraft's API testing services validate functionality, contracts, error handling and data integrity across REST, SOAP and GraphQL — using positive and negative cases to prove an endpoint behaves correctly, not just on the happy path.
This is the functional, correctness-focused API service — and it is one of three complementary API pages. API automation testing turns these checks into a CI-run suite; API security testing probes them for abuse and OWASP API risks. Most teams use all three; this one defines what 'correct' means. It sits under our functional testing umbrella.
our services
Our API Testing Services
We validate your API surface for correctness — behaviour, contracts and data — with both happy-path and negative coverage. Most engagements combine several of the services below.
Verify each endpoint returns the right response, status code and data for valid requests across your API surface.
Validate every response against its OpenAPI/Swagger, WSDL or GraphQL schema, so the implementation never drifts from the documented contract.
Malformed requests, invalid and missing fields, wrong types, unauthorized and missing-resource calls — confirming the API fails correctly, not silently.
Check that the data returned is accurate and consistent — calculations, relationships and state — not just well-formed.
Full coverage of REST and SOAP endpoints and GraphQL queries, mutations, schema and authorization rules.
Verify correctness across multi-endpoint flows where one call’s output feeds the next, mirroring real service interactions.
Flexible engagement models
A QA pod that owns your API correctness coverage, priced by endpoints kept under test rather than hours.
API QA engineers who plug into your existing process and tools under your leadership — scaled up or down monthly.
A defined set of endpoints validated end to end against their contracts — one agreed scope, one report.
tools & frameworks
Tools & Frameworks We Use
Tool choice is decided in Phase 1, against your API style and contracts — never by default. Functional API work spans request tooling, schema validation and SOAP/GraphQL clients:
Interactive request building and response validation across REST and GraphQL.
The standard for SOAP/WSDL functional and data-driven API testing.
Code-first response validation for precise, repeatable assertions.
Readable, assertion-rich API tests with built-in schema validation.
Strict validation that responses match their defined shape.
The contract validated against — catching spec-vs-implementation drift.
Query, mutation, schema and authorization-rule validation for GraphQL APIs.
Field-level checks on values, types and data integrity in responses.
why automate
Why API Testing Matters
The API is where your real logic and data live — and a defect there is invisible until a UI or a partner integration trips over it. Testing at the API catches correctness problems at the source, where they are cheapest and clearest to fix. Here is what it changes:
Every endpoint is proven to return the right data, status and shape — for valid and invalid requests alike.
Correctness defects are found at the API, not after they have rippled into the interface or a partner’s system.
Negative testing proves the API fails gracefully and correctly — the part that quietly breaks in production.
Checks on values, calculations and relationships keep your data accurate, not just well-formed.
Testing at the service layer pinpoints exactly where a problem is, instead of chasing it down through the UI.
Well-defined functional checks are exactly what becomes a CI API automation suite.
our process
Our API Testing Process
Every engagement follows the same disciplined path — and produces a concrete artifact at the end of each phase, so you always know exactly what you are getting.
Map the API & Contracts
We inventory your endpoints across REST, SOAP and GraphQL, gather the contracts (OpenAPI/Swagger/WSDL/schema), and prioritise by business risk.
→ artifact: API inventory + contract mapDesign Test Cases
We write functional and negative test cases per endpoint — valid responses, status codes, schema, data integrity, auth, and the error and edge cases that break things.
→ artifact: functional + negative test suiteValidate Responses
We execute the suite, validating each response for correctness — status, schema, field types, data integrity and proper error handling — logging every deviation.
→ artifact: per-endpoint validation resultsReport & Retest
We report defects with request/response evidence, verify fixes, and re-validate — and hand off to automation where the checks should run on every build.
→ artifact: defect reports + verified fixesSee a response validated
A sample inspection of a single endpoint — status code, schema, fields, types and data integrity all validated, with one error-handling case catching a correctness bug.
automate it
Automated & AI-Assisted API Testing
Functional API testing pairs naturally with automation and AI. Once correctness is defined, those checks should run continuously — so we hand them off to a CI suite and use AI to generate test cases and assertions from your OpenAPI spec and suggest negative cases worth adding.
A QA engineer reviews what the AI proposes — correctness is the whole point, so it cannot be left to a guess. For the continuously-run, maintained version of these checks, see our API automation testing services.
industries
Industries We Serve
We provide API testing for teams across industries where the data and logic behind the screen carry the real risk.
why us
Why Choose QACraft for API Testing
Teams choose QACraft when they want QA engineers who own outcomes — not a body shop billing hours.
We prove endpoints behave correctly — positive and negative — not just that they respond. Behaviour, not vibes.
Every response is checked against its OpenAPI/WSDL/GraphQL schema, so spec-vs-implementation drift is caught.
All test cases, collections and reports live in your repository from day one. No black boxes, no lock-in.
We catch defects at the API layer — earlier, faster and more precisely than testing through the UI.
Embed a dedicated pod, augment your team, or take a fixed-scope API test pass — scaled to your needs.
Functional API testing connects to your API automation, API security and functional testing under one team — joined-up, not stitched together.
straight answers
Frequently Asked Questions
What is API testing?
API testing verifies that your application’s APIs work correctly at the interface — that each endpoint returns the right status codes and data, matches its agreed contract and schema, handles authentication and errors properly, and keeps your data accurate. It tests the service layer directly, beneath and independent of any UI.
How is API testing different from API automation?
This page is functional API testing: validating that endpoints behave correctly — contracts, status codes, error handling, data integrity. API automation testing takes those checks and turns them into a maintained suite that runs in your CI/CD on every commit. Functional defines what 'correct' means; automation runs it continuously.
How is this different from API security testing?
Functional API testing asks 'does the endpoint return the right thing?'. API security testing asks 'can the endpoint be abused?' — auth bypass, injection, broken object-level authorization and other OWASP API risks. They are complementary; most teams need both.
Do you test REST, SOAP and GraphQL?
Yes — all three. REST and SOAP including status codes, payloads, headers and faults; GraphQL including queries, mutations, schema validation and authorization rules. We validate each against its contract, whatever the style.
Do you test error handling and negative cases?
Always — it is where the real defects hide. We send malformed requests, missing and invalid fields, wrong types, unauthorized calls and missing resources, and verify the API responds with the correct status code and a sensible error body, rather than crashing or silently returning the wrong thing.
Do you validate against our API contract or OpenAPI spec?
Yes. We validate responses against your OpenAPI/Swagger, WSDL or GraphQL schema, so a drift between the documented contract and the actual implementation is caught — protecting every consumer that relies on it.
Ready for APIs that behave correctly?
Build your plan in 60 seconds — or bring your API to a 30-minute call and leave with a contract-coverage picture and a single number.