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bdd-regression-test-generator

bdd-regression-test-generator

An autonomous agent that analyzes REST API endpoints and OpenAPI/Swagger service contracts to generate:

  • BDD Gherkin specifications (.feature files) describing all happy-path and edge-case scenarios.

  • TypeScript regression test scripts (Jest + Playwright-ready) ready to run against real services.

It exposes two interfaces:

Interface

Description

CLI

bdd-gen generate --input <spec> --output <dir>

MCP Server

Model Context Protocol server exposable to any MCP-aware host (e.g. IBM Bob, Claude Desktop)


Features

  • Parses OpenAPI 3.x and Swagger 2.0 contracts (JSON or YAML).

  • Extracts all paths, HTTP methods, parameters, request bodies, and response schemas.

  • Generates one .feature file per endpoint tag group.

  • Generates one *.spec.ts file per endpoint tag group with fully typed Jest test cases.

  • Supports custom base-URL injection at generation time.

  • MCP server exposes analyze_contract, generate_gherkin, and generate_tests tools.


Related MCP server: Swagger Testcase MCP

Installation

npm install
npm run build

To use as a global CLI after building:

npm link

CLI Usage

# Generate both Gherkin and Jest tests from an OpenAPI YAML spec
bdd-gen generate --input ./petstore.yaml --output ./generated --baseUrl https://api.example.com

# Generate only Gherkin feature files
bdd-gen generate --input ./petstore.json --output ./generated --only gherkin

# Generate only Jest test scripts
bdd-gen generate --input ./petstore.json --output ./generated --only jest

# Analyze a contract and print a summary (no file generation)
bdd-gen analyze --input ./petstore.yaml

CLI Options

Option

Alias

Description

Default

--input <path>

-i

Path to the OpenAPI/Swagger contract file

required

--output <dir>

-o

Directory where generated files will be written

./generated

--baseUrl <url>

-b

Base URL to embed in the generated test files

http://localhost:3000

--only <type>

Generate only gherkin or jest (omit for both)

both

--verbose

-v

Enable verbose logging

false


MCP Server

Start the MCP server with:

npm run mcp

The server registers the following tools:

analyze_contract

Parses an OpenAPI/Swagger contract from a file path or raw JSON/YAML string.

Input:

{ "source": "./petstore.yaml" }

Output: A structured ContractSummary JSON object with paths, methods, parameters, and schemas.


generate_gherkin

Generates Gherkin .feature content from a parsed contract.

Input:

{
  "source": "./petstore.yaml",
  "outputDir": "./generated"
}

Output: List of written .feature file paths.


generate_tests

Generates TypeScript Jest test scripts from a parsed contract.

Input:

{
  "source": "./petstore.yaml",
  "outputDir": "./generated",
  "baseUrl": "https://api.example.com"
}

Output: List of written .spec.ts file paths.


Project Structure

bdd-regression-test-generator/
├── src/
│   ├── parser/
│   │   └── contract-analyzer.ts   # OpenAPI/Swagger parser and extractor
│   ├── generator/
│   │   ├── gherkin-builder.ts     # Gherkin .feature file builder
│   │   └── jest-builder.ts        # TypeScript Jest spec builder
│   ├── mcp/
│   │   └── server.ts              # MCP server exposing generation tools
│   └── cli.ts                     # Commander-based CLI entry point
├── tests/
│   └── generator.test.ts          # Unit tests for parser and generators
├── dist/                          # Compiled output (after build)
├── package.json
├── tsconfig.json
└── README.md

Running Tests

npm test

With coverage:

npm run test:coverage

Example: Generated Gherkin

Feature: Pets

  Background:
    Given the API base URL is "https://api.example.com"

  Scenario: GET /pets - list all pets - success
    Given I have valid authentication credentials
    When I send a GET request to "/pets"
    Then the response status code should be 200
    And the response body should match the "PetList" schema

  Scenario: GET /pets - list all pets - unauthorized
    Given I have invalid or missing authentication credentials
    When I send a GET request to "/pets"
    Then the response status code should be 401

Example: Generated Jest Test

import axios from 'axios';

const BASE_URL = 'https://api.example.com';

describe('Pets', () => {
  describe('GET /pets', () => {
    it('should return 200 for a valid request', async () => {
      const response = await axios.get(`${BASE_URL}/pets`);
      expect(response.status).toBe(200);
    });
  });
});

License

MIT

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