Welcome to this hands-on **Koin tutorial** where we focus on setting up **dependencies** and creating **dummy API services** in a **Kotlin Android** project using **Koin for Dependency Injection**. If you're learning how to structure your app using DI or trying to replace Dagger/Hilt with something simpler and Kotlin-native, this video is for you!

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### What You’ll Learn:

In this tutorial, we’ll cover the **essential steps to integrate Koin** into your Android app. You’ll:

Add Koin dependencies to your project
Create a dummy API service interface and implementation
Define Koin modules to provide services and repositories
Inject dependencies into a ViewModel
Test the setup using logs or UI output

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### Prerequisites:

- Basic knowledge of Kotlin and Android Studio
- MVVM or similar architecture understanding
- Android project ready to integrate with Koin

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### Step-by-Step Guide:

1. **Add Koin to your `build.gradle` file**:
```kotlin
// In app-level build.gradle
implementation("io.insert-koin:koin-android:3.5.3")
implementation("io.insert-koin:koin-androidx-viewmodel:3.5.3")
```

2. **Create a Dummy API Interface:**
```kotlin
interface ApiService {
fun fetchData(): String
}
```

3. **Add a Fake Implementation:**
```kotlin
class DummyApiService : ApiService {
override fun fetchData(): String = "Fake API response"
}
```

4. **Create a Repository Using ApiService:**
```kotlin
class DataRepository(private val apiService: ApiService) {
fun getData(): String = apiService.fetchData()
}
```

5. **Define Your Koin Module:**
```kotlin
val appModule = module {
single ApiService { DummyApiService() }
single { DataRepository(get()) }
}
```

6. **Start Koin in your `Application` class:**
```kotlin
class MyApp : Application() {
override fun onCreate() {
super.onCreate()
startKoin {
androidContext(this@MyApp)
modules(appModule)
}
}
}
```

7. **Inject Dependencies into ViewModel:**
```kotlin
class MyViewModel(private val repository: DataRepository) : ViewModel() {
fun load(): String = repository.getData()
}
```
```kotlin
val viewModelModule = module {
viewModel { MyViewModel(get()) }
}
```

8. **Observe and Use in Activity/Fragment:**
```kotlin
val viewModel: MyViewModel by viewModel()
```

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### Bonus Tip:

Use `mockk` or any mocking library for testing your services with test-specific Koin modules.

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This tutorial is perfect for learning the **foundations of dependency injection with Koin**, especially in cases where you need to **mock or stub out real API calls** during development or testing.

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