API and data testing services built to catch problems at the source
A bug caught at the API layer is cheap to fix. The same bug caught in a UI test, or by a user, is not. GoGreenlit tests the layer underneath your interface: endpoints, contracts, schemas, and the data integrity checks that never show up on a screen but break production just as often.
Layers
What API testing actually covers
Real API testing goes well past checking for a 200 status code. These are the layers we actually test.
Functional testing
Every endpoint checked against its own documentation, response structure included, not just a passing status code.
Contract testing
Schema adherence between consumer and provider, so a change on one side of an integration gets flagged before it breaks the other.
Negative testing
Invalid input, malformed requests, and edge cases, checked for consistent, non-leaky error responses.
Security testing
Authentication, data access controls, and error messages checked for what they accidentally expose.
Schema validation
Responses checked against their schema on every run, so a breaking change gets caught in CI, not in a client integration.
Performance basics
Baseline response time validation under normal load, enough to catch a regression before it reaches a real performance test.
Tools
Tools we use, matched to your stack
Which tool we reach for depends on what your team already runs, not a fixed toolkit applied everywhere.
Postman
Exploratory testing and collection-based regression suites, run through Newman in CI.
REST Assured
A fluent Java library wired into TestNG or JUnit for teams already running a Java API suite.
PyTest with requests
Python API testing following the same Page Object Model discipline as our UI suites.
Pact
Contract testing across services, with broker integration so a breaking change is caught before it ships.
Data
Data integrity testing
The checks that never show up in an API response but break production just as often.
Business rule enforcement
Rules checked at the API layer and the database layer, so a bug that only shows up in the data gets caught too.
Boundary condition testing
The edge cases around a limit, not just the limit itself, where most data bugs actually live.
Database state verification
What actually landed in the database after an operation, checked directly, not inferred from the API response.
Idempotency verification
A duplicate request should not double-charge a customer or double-create a record. We test for that directly.
CI/CD
API tests in your CI/CD pipeline
A suite that only runs on demand catches problems too late. This is how it stays continuous.
- Pre-merge gates run a focused set of critical-path tests in under two minutes.
- Staging suites hit real services, CI suites hit mocked dependencies, each for what it is actually good at.
- Contract registries catch a breaking change between services before it ever reaches production.
Questions
Frequently asked questions
Related from QA Consulting
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