Dev Proxy — Simulates API failures, throttling, and chaos for robust app testing, without code changes.
Analyzed by Sai Pavan Gopularam · Developer Tools · API Testing · View on GitHub
- Stars: 831
- Forks: 89
- Commits last 30 days: 41
- Health: Active (41 commits this month)
- Language: C#
- License: MIT
What It Is
Dev Proxy is a command-line tool that acts like a network traffic controller for your applications. Imagine a flight simulator, but for your API calls: it lets you intentionally introduce turbulence (failures), headwinds (slow responses), or air traffic control delays (throttling) to see how your app handles stress.
This matters because most apps rely on external APIs. If those APIs fail, your app might crash, lose user data, or provide a terrible experience. Dev Proxy solves this by allowing developers to test these 'unhappy paths' easily, without writing temporary test code or waiting for real outages. It helps build more resilient software that can withstand real-world API instability.
License Verdict
MIT License — Build and Sell Freely — Commercial Use Approved • No Copyleft Restrictions
The MIT License is highly permissive. You can use, copy, modify, merge, publish, distribute, sublicense, and sell copies of the software. This includes using it in commercial products and services without needing to disclose your source code. There are no copyleft restrictions.
How to Use It
To get started, you'll need to install the Dev Proxy global tool via the .NET CLI. Once installed, you can run it and begin configuring rules to simulate API behaviors.
Prerequisites:
- .NET SDK (6.0+ recommended)
Estimated setup time: 10 minutes.
dotnet tool install --global Microsoft.DevProxy
devproxy --version
devproxy --urls http://localhost:8000What I'd Build With This
API Resilience Scenario Builder (micro-saas)
Build a simple web or desktop application that provides a user-friendly GUI to configure complex Dev Proxy scenarios. Users could select common API endpoints, choose failure types (e.g., 500 errors, specific latency, rate limits), and generate the `.json` configuration files for Dev Proxy. This product targets individual developers or small teams who want to quickly set up advanced API testing without deep diving into JSON configs.
Effort: 3 Weeks Build Time · Target: Indie Developers, Small Dev Teams · Pricing: $19/mo or $149 one-time
Hosted API Reliability Testing Platform (saas)
Develop a cloud-based SaaS platform that integrates Dev Proxy's capabilities into a CI/CD pipeline. Developers upload their OpenAPI specs, define resilience tests (e.g., 'what if this API returns 429 for 10% of requests?'), and the platform runs tests against their staging environments using hosted Dev Proxy instances. It provides detailed reports on application behavior under stress. This targets mid-sized and large development teams focused on microservice reliability.
Effort: 6 Months Build Time · Target: Mid-sized Dev Teams, QA Teams · Pricing: $99-$499/mo based on usage
Custom Chaos Engineering Integration for Enterprises (enterprise)
Offer professional services to large enterprises to integrate Dev Proxy deeply into their existing testing frameworks and internal tooling. This would involve custom adapters for their specific API gateways, bespoke reporting, and training programs for their engineering teams on how to implement chaos engineering practices using Dev Proxy. The service would help large organizations ensure the resilience of their critical applications and microservices in complex environments.
Effort: Ongoing Service · Target: Large Enterprises, Financial Institutions · Pricing: $50k-$250k+ per project
Sai Pavan Gopularam's Take
Dev Proxy is a smart tool for any developer who's tired of 'it works on my machine' excuses. It lets you break things intentionally to build them stronger, which is invaluable for shipping robust software. I'd bet a simple GUI wrapper for common M365 API failure scenarios could easily pull in $500/month from busy developers.
Watch Out For
- Configuration Complexity: While powerful, setting up specific and nuanced failure scenarios can involve detailed JSON configuration, which might have a learning curve for new users.
- Proxy Interference: As a network proxy, Dev Proxy intercepts all traffic. Misconfiguration or running it alongside other network tools could lead to unexpected behavior or debugging challenges.
- Limited Scope: Dev Proxy simulates API issues, but it doesn't test other types of failures like database outages, network partitioning between services, or infrastructure-level chaos. It's one tool in a larger reliability toolkit.
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