API Testing & Postman Cheat Sheet

HTTP methods, status codes, request structure, Postman collections, environments, and test assertions.

Web & Network

api

postman

testing

API testing verifies that endpoints behave as documented: correct methods, status codes, headers, and response bodies. Postman organizes requests into collections with reusable environments and scripted assertions.

HTTP methods

Table

Method	Purpose
`GET`	Read a resource.
`POST`	Create a resource.
`PUT`	Replace a resource.
`PATCH`	Partially update a resource.
`DELETE`	Remove a resource.
`HEAD`	Read headers only.
`OPTIONS`	Discover allowed methods (CORS).

Common status codes

Table

Code	Meaning
`200`	OK.
`201`	Created.
`204`	No content.
`400`	Bad request.
`401`	Unauthenticated.
`403`	Forbidden.
`404`	Not found.
`422`	Unprocessable entity (validation).
`429`	Rate limited.
`500`	Server error.

Postman test assertions

pm.test("Status is 200", () => pm.response.to.have.status(200));
pm.test("Body has id", () => {
  const json = pm.response.json();
  pm.expect(json.id).to.be.a("string");
});
pm.test("Response time OK", () => {
  pm.expect(pm.response.responseTime).to.be.below(500);
});

Environments and variables

Table

Scope	Example
Global	Shared across all collections.
Collection	Scoped to one collection.
Environment	Per-environment (dev/staging/prod).
Local	Per-request temporary.

Use {{baseUrl}}/users with an environment variable baseUrl to switch hosts without editing requests.

References

Related tools

Postman Collection Builder