Migrating from Mountebank to Rift: A Zero-Friction Guide¶

Switch to 20-250x better performance without changing a single line of configuration

You're using Mountebank. Your team has invested time building mock configurations, your CI/CD pipelines are set up, and your tests depend on it. The thought of migration sounds daunting.

Here's the good news: migrating to Rift takes about 5 minutes.

Rift is designed as a drop-in replacement. Same API. Same configuration format. Same behavior. Just faster. Much faster.

The 5-Minute Migration¶

Step 1: Swap the Docker Image¶

Before (Mountebank):

docker run -p 2525:2525 mountebank/mountebank:2.9.1

After (Rift):

docker run -p 2525:2525 zainalpour/rift-proxy:latest

That's it. Your existing imposters.json files work without modification.

Step 2: Update docker-compose.yml¶

Before:

services:
  mountebank:
    image: mountebank/mountebank:2.9.1
    ports:
      - "2525:2525"
      - "4545:4545"
    volumes:
      - ./imposters.json:/imposters.json
    command: --configfile /imposters.json --allowInjection

After:

services:
  rift:
    image: zainalpour/rift-proxy:latest
    ports:
      - "2525:2525"
      - "4545:4545"
    volumes:
      - ./imposters.json:/imposters.json
    command: --configfile /imposters.json --allow-injection

Note: --allowInjection becomes --allow-injection (both are supported for compatibility).

Step 3: Update CI/CD¶

If you're pulling from Docker Hub, update the image reference:

# GitHub Actions example
jobs:
  test:
    services:
      rift:
        image: zainalpour/rift-proxy:latest
        ports:
          - 2525:2525

Compatibility Checklist¶

Feature	Mountebank	Rift	Notes
REST API	✅	✅	Identical
JSON config format	✅	✅	Identical
`equals` predicate	✅	✅
`deepEquals` predicate	✅	✅
`contains` predicate	✅	✅
`startsWith` predicate	✅	✅
`endsWith` predicate	✅	✅
`matches` (regex)	✅	✅
`exists` predicate	✅	✅
`jsonpath` predicate	✅	✅	247x faster
`xpath` predicate	✅	✅	170x faster
`and`/`or`/`not`	✅	✅
`is` response	✅	✅
`proxy` response	✅	✅
`inject` response	✅	✅	JavaScript
`wait` behavior	✅	✅
`decorate` behavior	✅	✅
`copy` behavior	✅	✅
`lookup` behavior	✅	✅
`repeat` behavior	✅	✅
Response cycling	✅	✅
Request recording	✅	✅
HTTPS	✅	✅
Mutual TLS	✅	✅

Validating Your Migration¶

Using rift-verify¶

Rift includes a verification tool that tests your imposters automatically:

# Start Rift with your config
docker run -d -p 2525:2525 -p 4545:4545 \
  -v $(pwd)/imposters.json:/imposters.json \
  zainalpour/rift-proxy:latest \
  --configfile /imposters.json

# Run verification (rift-verify ships with the Homebrew formula and the release archives)
rift-verify --admin-url http://localhost:2525

The verifier: - Fetches all imposters - Generates test requests from predicates - Verifies responses match expectations - Reports any mismatches

Using rift-lint¶

Validate configuration before deployment:

# Check for issues
rift-lint ./imposters/

# Strict mode (CI/CD)
rift-lint ./imposters/ --strict

# Auto-fix common issues
rift-lint ./imposters/ --fix

Migration Scenarios¶

Scenario 1: Kubernetes Deployment¶

Before:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: mountebank
spec:
  template:
    spec:
      containers:
        - name: mountebank
          image: mountebank/mountebank:2.9.1
          ports:
            - containerPort: 2525

After:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: rift
spec:
  template:
    spec:
      containers:
        - name: rift
          image: zainalpour/rift-proxy:latest
          ports:
            - containerPort: 2525
          resources:
            # Rift uses significantly less memory
            limits:
              memory: "128Mi"  # vs 512Mi+ for Mountebank
              cpu: "500m"

Scenario 2: Node.js Test Suite¶

If you're using the mountebank npm package:

Before:

const mb = require('mountebank');

const server = await mb.create({ port: 2525 });

After:

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

const server = await rift.create({ port: 2525 });

The API is intentionally similar. Most test code requires minimal changes.

Scenario 3: Python Tests with requests¶

No changes needed — you're calling the REST API:

import requests

# This works with both Mountebank and Rift
def create_imposter(port, stubs):
    requests.post('http://localhost:2525/imposters', json={
        'port': port,
        'protocol': 'http',
        'stubs': stubs
    })

Common Migration Issues¶

Issue 1: EJS Templates¶

Mountebank supports EJS templates in config files. Rift currently processes these statically at load time.

Solution: Pre-process EJS files or use environment variable substitution:

# Use envsubst
envsubst < imposters.template.json > imposters.json
rift --configfile imposters.json

Issue 2: File Includes¶

Mountebank's <%- include('...') %> syntax works in Rift for reading files (certificates, etc.):

{
  "protocol": "https",
  "key": "<%- include('/certs/key.pem') %>",
  "cert": "<%- include('/certs/cert.pem') %>"
}

Issue 3: Custom Mountebank Protocols¶

Rift currently supports HTTP/HTTPS. TCP and SMTP protocols are planned.

Workaround: Run Mountebank alongside Rift for unsupported protocols:

services:
  rift:
    image: zainalpour/rift-proxy:latest
    ports:
      - "2525:2525"
      - "4545-4555:4545-4555"  # HTTP mocks

  mountebank:
    image: mountebank/mountebank:2.9.1
    ports:
      - "2526:2525"
      - "4556-4560:4556-4560"  # TCP/SMTP mocks

Performance Comparison¶

After migration, you'll notice immediate improvements:

Startup Time¶

# Mountebank with 10 imposters
time docker run mountebank/mountebank --configfile imposters.json
# ~3-5 seconds

# Rift with 10 imposters
time docker run zainalpour/rift-proxy --configfile imposters.json
# ~0.5 seconds

Memory Usage¶

# Mountebank
docker stats mountebank
# CONTAINER   CPU %   MEM USAGE
# mountebank  0.50%   180MiB

# Rift
docker stats rift
# CONTAINER   CPU %   MEM USAGE
# rift        0.10%   15MiB

Request Throughput¶

Run a quick benchmark:

# Install hey
brew install hey

# Benchmark
hey -n 10000 -c 50 http://localhost:4545/api/users

You'll see significantly higher requests per second with Rift.

Gradual Migration Strategy¶

For large teams, consider a gradual approach:

Phase 1: New Projects¶

Use Rift for all new test suites and services.

Phase 2: Non-Critical Tests¶

Migrate integration tests that run frequently (biggest performance gain).

Phase 3: Full Migration¶

After validation, migrate remaining Mountebank usage.

Parallel Running¶

During transition, run both in parallel:

services:
  rift:
    image: zainalpour/rift-proxy:latest
    ports:
      - "2525:2525"
    environment:
      - RUST_LOG=info

  mountebank:
    image: mountebank/mountebank:2.9.1
    ports:
      - "2526:2525"  # Different port

Route traffic based on test suite or feature flag.

Migration Checklist¶

[ ] Update Docker image reference
[ ] Update docker-compose.yml
[ ] Update CI/CD configuration
[ ] Run rift-lint on configuration files
[ ] Run rift-verify to validate imposters
[ ] Run existing test suite
[ ] Monitor for any behavioral differences
[ ] Update documentation

Getting Help¶

Encountering issues? Here's where to get help:

Documentation: achird-labs.github.io/rift
GitHub Issues: Report bugs or compatibility issues
Examples: Check the examples directory for patterns

What's Next?¶

You've migrated to Rift. Now let's explore advanced features:

Next Post: Mastering Request Matching with Predicates
Coming Soon: Chaos Engineering with Fault Injection

Successfully migrated? Share your experience! How much faster are your tests running?

Tags: #Migration #Mountebank #Rift #APITesting #DevOps #Performance