Fakt¶

Compile-time type-safe test fakes for Kotlin Multiplatform

Automate the fake-over-mock pattern. Fakt generates type-safe test doubles that eliminate boilerplate.

@Fake
interface Analytics {
    fun track(event: String)
}

val fake = fakeAnalytics {
    track { event -> println("Tracked: $event") }
}

Why Fakt?¶

Manual fakes scale poorly - Each type needs custom tracking, config, or cleanup code
Manual fakes rot over time - Behavior diverges from real implementations without compile-time warnings
Mocks verify interactions, not behavior - Testing how dependencies are called, not what code achieves
Mocks make refactoring painful - Tests break even when behavior stays correct
Google explicitly prefers fakes - Lightweight, framework-free, and resilient to refactoring
Compile-time generation solves both problems - Automated fakes that never drift from interfaces

Read the full story →

✨ Features¶

✅ Zero boilerplate - Compiler generates type-safe fakes automatically at build time
✅ Never drift from real code - Interface changes cause compile errors, not silent bugs
✅ Test what matters - Verify outcomes (state) instead of implementation details (calls)
✅ Works everywhere - All KMP targets without reflection, zero production dependencies
✅ Smart defaults - Sensible behaviors for all types, configure only what you need
✅ Real code, not magic - Generated .kt files are readable, not bytecode magic

Complete feature reference →

🚀 Getting Started¶

Quick Start:

Getting Started - Install Fakt and create your first fake in 5 minutes
Usage Guide - Core patterns and techniques
Testing Patterns - Best practices for using fakes in tests

Usage Topics:

Suspend Functions - Working with coroutines and async code
Generics - Generic interfaces and type parameters
Properties - Faking val and var properties
Call Tracking - StateFlow-based reactive counters

Advanced Topics:

Multi-Module Setup - Cross-module fakes with collector modules
Configuration - Plugin configuration and log levels
Performance - Build times, caching, and optimization
Migration from Mocks - Migrating from MockK or Mockito

Reference:

API Reference - Complete generated API documentation
Limitations - Known limitations and workarounds
Compatibility - Platform and version requirements
FAQ - Frequently asked questions
Troubleshooting - Common issues and solutions

🌐 Platform Support¶

Fakt works on all Kotlin Multiplatform targets without reflection: JVM, Android, iOS, macOS, Linux, Windows, JavaScript, WebAssembly, watchOS, tvOS.

Single-platform projects (JVM-only, Android-only) are fully supported.

Full compatibility matrix →

Requirements¶

Kotlin: 2.2.21+
Gradle: 8.0+
JVM: 11+

License¶

Fakt is licensed under the Apache License 2.0.

Copyright (C) 2025 Rodrigo Sicarelli

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.