Mockzilla

What is Mockzilla?

A solution for running and configuring a local HTTP server to mimic REST API endpoints used by your Android, iOS, Flutter, or Kotlin Multiplatform application.

The source code is written in Kotlin but is fully compatible with Swift, Dart bindings are also provided!

Advantages

✅ Compile safe mock endpoint definitions.

✅ HTTP client agnostic.

✅ Works completely offline.

✅ Entirely self-contained in your application's codebase.

✅ Edit responses live from a desktop app or an in-app overlay — no rebuild required.

✅ Presets for one-tap switching between success, error, and edge-case responses.

Control mocks live, while your app runs 🎛️

Beyond defining mocks in code, Mockzilla ships two ways to change what's returned while your app is running — force an endpoint to fail, add artificial latency, or apply a preset, all without touching code or rebuilding:

• Mockzilla Desktop: A companion app that connects to your device over Wifi.
• Mockzilla Mobile UI: An overlay you embed directly in your app.

Quick Start 🚀

Head to the quick start guide to get up and running, or jump straight to a specific topic:

• Configuring Endpoints
• Mockzilla Desktop
• Mockzilla Mobile UI
• Presets

Why's it useful? 🙌

Development servers go down, endpoints can be late being delivered or not exist at all! Mockzilla aims to easily provide a way of simulating your server from within your mobile application's codebase.

Why not use a hosted solution? ☁️

Hosted mocking solutions can be powerful mocking tools in many cases. They have their downsides:

1. They can go down, Mockzilla works offline!
2. There's no compile-time checking
3. They require active maintenance with no compile-time safety if APIs change.

What makes it compile safe? 🖥️

By defining your mocks using the same model classes as are used for deserialization, changing them, means changing the mocks or we get compiler errors! 😎

Example using kotlinx.serialization:

Existing networking models

@Serializable
data class HelloWorldResponse(val greeting: String)

Mocking code

val myEndpoint = EndpointConfiguration.Builder("hello-world")
    .setPatternMatcher { uri.endsWith("hello-world") }
    .setDefaultHandler {
        MockzillaHttpResponse(
            body = Json.encodeToString(
                // Using existing models
                HelloWorldResponse(greeting = "Hello world!")
            )
        )
    }

Important Note 🛑

Mockzilla is designed as a development and test tool only.

Mockzilla should never be used in production. Its traffic is unprotected and by nature of running a server on device, it can introduce security issues.

Do not ship it to production.

Contributing

Contributions are welcome! See CONTRIBUTING.md for how to get set up.