Kotlin/Gradle/JUnit starter project

Just a quick tutorial to start a blank new Kotlin project using Gradle. Optionally, JUnit can also be added.

1. Create a project

1. Download and install IntelliJ Community, free for Java/Kotlin projects. Alternatively, you can use IntelliJ Ultimate EAP (no subscription required).
2. Go to “File” ⇀ “New project”.
3. Activate “Create Git repository”.
4. Pick “Kotlin” as language.
5. Pick “Gradle” as the build system.
6. Pick “Kotlin” as Gradle DSL. Since we’re using Kotlin, it makes sense that the Gradle DSL is Kotlin.
7. Fill in the remaining details, and press “Create”.

2. Setup Git

To ensure you don’t lose your work and can always go back in time, ensure you set up Git — even if only locally.

1. Start a new git repository (git init) if you haven’t picked “Create Git repository” before.
2. Create a .gitignore file with the following content, and commit all the changes:

/.gradle
/.idea
/build

3. Update Gradle/Kotlin

The IDE doesn’t use the latest versions of Gradle and Kotlin, so we need to do it manually.

1. Check the latest version of Gradle (e.g. 7.4.2) and update the file gradle/wrapper/gradle-wrapper.properties accordingly.
2. Check the latest version of Kotlin (e.g. 1.6.21) and update the file build.gradle.kts accordingly.

plugins {
    kotlin("jvm") version "1.6.21".  // or 1.+ for always latest
}

4. Set up JUnit

1. At build.gradle.kts’s dependencies, set up JUnit 5:

dependencies {
   testImplementation("org.junit.jupiter:junit-jupiter-api:5.+")
   testRuntimeOnly("org.junit.jupiter:junit-jupiter-engine:5.+")
}
tasks.withType<Test> {
    useJUnitPlatform()
}

2. Create a dummy test (src/test/kotlin/DummyTest.kt) and run it just to prove that the JUnit setup is good:

class TestAmazonCart {
   @Test
   fun `everything is fine`() {
       assertTrue(true)
   }
}

You can also run the tests with ./gradlew test