Rift

High-performance Mountebank-compatible HTTP/HTTPS mock server written in Rust

Rift is a drop-in replacement for Mountebank that provides 2-250x better performance while maintaining full API compatibility. Use your existing Mountebank configurations and enjoy faster test execution.

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Why Rift?

Drop-in Mountebank Replacement

Rift implements the Mountebank REST API, allowing you to:

  • Use existing Mountebank configuration files without changes
  • Keep your current test infrastructure and tooling
  • Switch between Mountebank and Rift transparently

Blazing Fast Performance

Built in Rust with async I/O, Rift delivers exceptional performance:

Feature Mountebank Rift Speedup
Simple stubs 8,898 RPS 214,818 RPS 24x faster
Regex (100th pattern) 112 RPS 207,024 RPS 1,857x faster
JSONPath predicates 4,312 RPS 199,404 RPS 46x faster
API stub — no match (404) 1,351 RPS 209,763 RPS 155x faster
Complex predicates 4,703 RPS 191,987 RPS 41x faster

Apple M4 laptop, 50 connections, median of 3 repetitions. On a 16-vCPU AMD EPYC server the same suite reaches 325k RPS and 6,160x on regex — but Mountebank is slower there, so the M4 figures above are the conservative read.

See the performance page for both hosts, the full suite, and the method.

Full Feature Compatibility

Rift supports all major Mountebank features:

  • Imposters - HTTP/HTTPS mock servers on any port
  • Stubs - Request matching with responses
  • Predicates - equals, contains, matches, exists, jsonpath, xpath, and, or, not
  • Responses - Static, proxy, injection with behaviors
  • Behaviors - wait, decorate, copy, lookup
  • Recording - Proxy mode with response recording

Quick Start 

# Pull the latest image (from GitHub Container Registry)
docker pull zainalpour/rift-proxy:latest

# Or from Docker Hub
docker pull zainalpour/rift-proxy:latest

# Run Rift (Mountebank-compatible mode)
docker run -p 2525:2525 zainalpour/rift-proxy:latest

Create Your First Imposter 

# Create an imposter that responds to GET /hello
curl -X POST http://localhost:2525/imposters \
  -H "Content-Type: application/json" \
  -d '{
    "port": 4545,
    "protocol": "http",
    "stubs": [{
      "predicates": [{ "equals": { "method": "GET", "path": "/hello" } }],
      "responses": [{ "is": { "statusCode": 200, "body": "Hello, World!" } }]
    }]
  }'

# Test the imposter
curl http://localhost:4545/hello
# Output: Hello, World!

Using an Existing Mountebank Config 

# Start Rift with your existing imposters.json file
docker run -p 2525:2525 -v $(pwd)/imposters.json:/imposters.json \
  zainalpour/rift-proxy:latest --configfile /imposters.json

Node.js Integration

For Node.js projects, use the official npm package:

npm install @rift-vs/rift

import rift from '@rift-vs/rift';

// Start a Rift server (drop-in replacement for Mountebank)
const server = await rift.create({ port: 2525 });

// Create imposters, run your tests...

await server.close();

See the Node.js Integration Guide for complete documentation.

Java / JVM Integration

For JVM projects, use the official rift-java SDK. It runs the engine three ways — embedded in-process (Panama FFM, no Docker), connected to any running admin endpoint, or as a managed spawned binary — with a fluent DSL plus JUnit 5, Spring, and Testcontainers integrations.

<dependency>
  <groupId>io.github.achird-labs</groupId>
  <artifactId>rift-java-core</artifactId>
  <scope>test</scope>
</dependency>

try (Rift rift = Rift.embedded()) {                  // or Rift.connect(uri) / Rift.spawn()
    Imposter users = rift.create(
        imposter("users").stub(onGet("/api/users/1").willReturn(okJson("{\"id\":1}"))));
    // point your system under test at users.uri(), then assert:
    users.verify(onGet("/api/users/1"), times(1));
}

See the rift-java documentation for the full feature surface, and the BOM for version-pinning every module at once.

Documentation

Getting Started

Concepts

Mountebank Compatibility (reference)

  • Imposters - Creating and managing mock servers
  • Predicates - Request matching (equals, contains, regex, jsonpath, xpath)
  • Responses - Configuring stub responses
  • Behaviors - Response modification (wait, decorate, copy)
  • Proxy Mode - Recording and replaying responses

Configuration

Features

Deployment

Reference

Embedding & Extension

Project Status

Rift is under active development. Current status:

Feature Status
HTTP Imposters Stable
HTTPS Imposters Stable
All Predicates Stable
Static Responses Stable
Proxy Mode Stable
Behaviors (wait, decorate) Stable
Injection (JavaScript) Stable
TCP Protocol Planned
SMTP Protocol Planned

License

Rift is distributed under the Apache License 2.0.