API testing · Postman
API testing services with Postman
Thorough tests for the layer under your screens: contracts, negative paths, authentication and data validation, organised in Postman collections your team can run and extend.
Best for: Teams with REST APIs behind web or mobile apps, including payment, onboarding and partner integrations.
The problem
Most serious defects hide below the user interface.
- UI tests pass, but the API accepts invalid or incomplete data.
- Integrations with payment providers or partners break without warning.
- Error handling and edge cases have never been tested on purpose.
- There is no shared, repeatable collection of API checks.
The approach
Structured API coverage, from happy paths to failure modes.
Tessellate maps your endpoints and business rules, then builds Postman collections that cover expected behaviour, negative and boundary cases, authentication and authorisation, and data validation. Collections can run on demand or in your pipeline, so API changes are checked before they reach your users or partners.
What you get
- API test plan based on your endpoints, specs and business rules
- Postman collections and environments, organised by feature
- Positive, negative and boundary tests with clear assertions
- Authentication, authorisation and error-handling checks
- Option to run collections in CI
- Defect reports with requests, responses and steps to reproduce
How it works
Four steps. No surprises.
- 01
Discover
Review API documentation, environments and known risk areas.
- 02
Map
Agree endpoints, scenarios and test data for each feature.
- 03
Test
Build and run collections, and report defects as they are found.
- 04
Report
Summarise coverage and findings, and hand over the collections.
Pricing
Clear scope, agreed before work starts.
Often a fixed-scope package for a defined set of endpoints, or part of a monthly retainer for ongoing releases. Rates are confirmed after a short discovery call.
FAQ
Questions about api testing
Which types of APIs do you test?
The focus is REST APIs tested with Postman. If you use other API styles, raise it in the discovery call and we will confirm fit.
Do you need our API documentation?
Documentation such as an OpenAPI specification helps, but it is not required. Tests can also be built from existing requests, code reviews and conversations with your developers.
Can API tests run in our pipeline?
Yes. Postman collections can be run from the command line in most CI services, so they can run on every build or deployment.
How is test data handled?
The test data approach is agreed up front. Dedicated test environments and synthetic or masked data are preferred over real customer records.
Related
Services that fit together
Ready to close the gaps?
Book a free discovery call. You will get a clear scope and a quote, with no obligation.