Sending a request and eyeballing the response is manual testing. To automate, you add assertions — checks that automatically decide whether the response is correct. In Postman these live in the "Tests" tab and run after each request.
What to assert
- Status code — e.g. the response is 200.
- Response time — e.g. under 500 ms.
- Body content — specific fields have expected values.
- Schema — the body matches an expected structure.
From request to automated pass/fail
Send request
→
Run assertions
→
Pass / fail result
Running a whole collection
Once your requests have assertions, Postman's Collection Runner (or the command-line runner) executes them all in sequence and reports pass/fail for each. That runner can then be triggered automatically in a CI/CD pipeline — the bridge to true automation.
Key step: assertions are what turn a request into a test. Without them, you are only sending calls; with them, Postman can judge correctness for you, every time.
Conclusion
Assertions make Postman requests self-checking, and the collection runner executes them at scale. This is the point where API testing becomes automation — repeatable, fast, and ready for a pipeline.