# API Testing

> 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. Use when this capability is needed.

- Skill: `tomevault-io/api-testing-4` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/api-testing-4`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/api-testing-4/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/api-testing-4

---


# API Testing with Postman + Newman

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

## Setup

```bash
npm install -g newman
```

## Test Pattern

Each request gets tests in the Tests tab:

```javascript
// 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:

```javascript
// 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

```javascript
// 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

```bash
# 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.

---
> Converted and distributed by [TomeVault](https://tomevault.io/claim/aiqualitylab) — claim your Tome and manage your conversions.
<!-- tomevault:4.0:skill_md:2026-04-13 -->