kotlin-hands-on/kotlin-junit-sample

A sample project demonstrating how to write tests in Kotlin for Java applications. This project shows the migration path from Java tests to Kotlin tests while testing Java source code.

Kotlin JUnit Sample

Tutorial: Test code using JUnit in JVM

Configuration guides: Maven | Gradle

A sample project demonstrating how to write tests in Kotlin for Java applications. This project shows how to add a Kotlin test for testing Java source code.

Getting Started

Prerequisites

• Java 17 or higher

Running Tests

Using Maven:

cd initial  # or cd complete
./mvnw test

Using Gradle:

cd initial  # or cd complete
./gradlew test

Project Structure

This repository contains two versions of the same project:

kotlin-junit-sample/
├── initial/          # Starting point with Java tests
│   ├── src/
│   │   ├── main/java/    # Java source code
│   │   └── test/java/    # JUnit test in Java
│   ├── pom.xml           # Maven configuration
│   └── build.gradle.kts  # Gradle configuration
│
└── complete/         # Final version with Kotlin tests
    ├── src/
    │   ├── main/java/    # Same Java source code
    │   └── test/java/    # Same JUnit test in Java, new test in Kotlin
    ├── pom.xml           # Maven with Kotlin support
    └── build.gradle.kts  # Gradle with Kotlin plugin

Application Code

Both projects contain a simple Todo application with:

• TodoItem − a Java class representing a todo item with title, description, completion status, and timestamps
• TodoRepository − a Java repository class for managing todo items in memory

Test Code

• initial/: Contains a JUnit 5 test written in Java for the TodoItem class
• complete/: Contains an additional Kotlin test for the TodoRepository class, demonstrating idiomatic Kotlin testing patterns

Technologies

• Java: 17
• Kotlin: 2.2.21 (test code only in the complete version)
• JUnit: 5.11.0
• Build Tools: Maven and Gradle (both supported)
• UI Library: Jexer 1.6.0 (terminal UI library)