Turn an OpenAPI spec into a running Postman suite.

Point it at a Swagger 2.0 or OpenAPI 3.x document and it generates a full Postman collection — auth, example bodies, JSON Schema assertions, and negative tests — ready to run with Newman.

The generator is deterministic. An optional AI planner may propose operation order and variable mappings — it never writes the Postman scripts.

View source →

bash

$ openapi-postman generate --spec ./petstore.openapi.yaml --negative

Generated 8 requests
Collection:   ./generated/api.collection.json
Environment:  ./generated/api.environment.json

$ openapi-postman run --collection ./generated/api.collection.json

✓ report.html · junit.xml · newman.json

Input, process, output.

One route from the fixture used on this page — POST /pets in fixtures/petstore.openapi.yaml — traced from spec to generated request.

Input · openapi.yaml

  /pets:
    post:
      summary: Create pet
      requestBody:
        content:
          application/json:
            schema: { $ref: '#/NewPet' }
      responses:
        '201':
          content:
            application/json:
              schema: { $ref: '#/Pet' }

  NewPet:
    required: [name]
    properties:
      name: { example: Miso }
      status: { enum: [available, adopted] }

⟶

Process · generator.ts

Resolve $ref chains, merge allOf
Merge path + operation parameters
Pick a security scheme, build auth block
Build an example body from the schema
Emit pm.test() assertions
Add negative variants (missing field, invalid enum, unauthorized)

⟶

Output · Postman item

"method": "POST",
"url": "{{baseUrl}}/pets",
"auth": { "type": "bearer" },
"body": {
  "raw": "{ \"name\": \"Miso\",
    \"status\": \"available\" }"
}

// event[0].script.exec
pm.test("Status code is successful (201)", …)
pm.test("Response time is below 2000ms", …)
pm.test("Response matches the schema…", …)

One command, a full Postman suite.

The generated collection for the Pets API above, folders and negative tests included — exactly what generate --negative produced for this page.

Pets

POSTCreate pet

POST[Negative] Create pet - unauthorized

POST[Negative] Create pet - missing name

POST[Negative] Create pet - invalid status

GETList pets

GET[Negative] List pets - unauthorized

GETGet pet

GET[Negative] Get pet - unauthorized

openapi-postman run executes the collection with Newman and writes three reports:

report.htmlstandalone, human-readable summary

junit.xmlfor CI test-result panels

newman.jsonraw run data, per-assertion detail

Built for real specs, not happy-path demos.

Spec formats: Swagger 2.0 and OpenAPI 3.x, from a local file or a URL
Bodies: JSON, form-urlencoded, multipart uploads, text, and binary responses
Parameters: Path, query, header, cookie, array, and deep-object styles
Auth: Bearer, Basic, OAuth token placeholders, API keys, and combined security requirements
Assertions: Status-specific JSON Schema checks, media-type-aware response handling
Ordering & chaining: CRUD-oriented default order, configurable, with identifier extraction between dependent requests
Negative tests: Missing-field, invalid-enum, boundary, and unauthorized cases — optional, off by default
Safe mode: Excludes DELETE operations when testing against an unfamiliar API
Runner: Newman execution with CLI, JSON, JUnit, and standalone HTML reports

—

Optional: AI-assisted planning

A provider-neutral planner can propose operation order and variable mappings from a read-only prompt, with schema-validated output and automatic fallback between providers. The deterministic generator still writes every Postman script.

OpenAI SDK Codex CLI Claude Code CLI Antigravity CLI Custom command

From spec to suite in three commands.

Install

$ npm install -g openapi-postman-test-generator
$ npm install -g newman

Generate

$ openapi-postman generate --spec ./openapi.yaml --negative --safe

Run

$ openapi-postman run --collection ./generated/api.collection.json --environment ./generated/api.environment.json