api-testing

name	api-testing
description	Generate and run REST API tests using Postman collections and Newman CLI. Use when asked to test APIs, verify endpoints, validate responses, or run Postman tests in CI.

API Testing with Postman + Newman

Generate API tests as Postman collections. Run them with Newman CLI.

Setup

npm install -g newman

Test Pattern

Each request gets tests in the Tests tab:

// Assert status code
pm.test("Status is 200", function () {
    pm.response.to.have.status(200);
});

// Assert response body
pm.test("Returns user name", function () {
    pm.expect(pm.response.json().name).to.eql("Test User");
});

// Assert response time
pm.test("Response under 2s", function () {
    pm.expect(pm.response.responseTime).to.be.below(2000);
});

// Validate schema
pm.test("Matches schema", function () {
    pm.response.to.have.jsonSchema({
        type: "object",
        required: ["id", "name", "email"],
        properties: {
            id: { type: "number" },
            name: { type: "string" },
            email: { type: "string" }
        }
    });
});

Pass Data Between Requests

Save a value from one response, use it in the next:

// In POST /users Tests tab — save created ID
const id = pm.response.json().id;
pm.environment.set("created_id", id);

// In GET /users/{{created_id}} — it auto-resolves

Negative Tests

// Missing required field → expect 400 or 422
pm.test("Rejects missing field", function () {
    pm.expect(pm.response.code).to.be.oneOf([400, 422]);
});

// No auth token → expect 401
pm.test("Rejects unauthorized", function () {
    pm.response.to.have.status(401);
});

Run with Newman

# Basic run
newman run collection.json

# With environment
newman run collection.json -e environment.json

# Override variables
newman run collection.json --env-var "base_url=https://staging.example.com"

# Data-driven from CSV
newman run collection.json -d testdata.csv

# CI report
newman run collection.json -r junit --reporter-junit-export report.xml

Guidelines

• Use environment variables for base_url and secrets, never hardcode.
• One assertion per pm.test block.
• Assert status code first, then body.
• Export collections as v2.1 format.