Unit testing your Kotlin code

Let’s start with our simple little Calculator class

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package com.putridparrot
 
class Calculator {
    fun add(a : Int, b : Int): Int{
        return a + b
    }
}

Creating our unit test(s)

Add a Kotlin class file and copy the following code into it

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package com.putridparrot
 
import kotlin.test.assertEquals
import org.junit.Test as test
 
class TestCalculator() {
    @test fun testAdd() {
        val c = Calculator()
 
        assertEquals(c.add(5, 2), 7)
    }
}

IntelliJ will help us add the dependencies, but if you need to add them manually, select File | Project Structure and in the Project Settings | Modules we need to add JUnit4.

Obviously we’re able to import Java compiled code into our project as Kotlin and Java share the JVM bytecode, so in this instance we’re using JUnit’s Test annotation (renaming to test for this example), we’re also using Kotlin, test assertions.

That’s all there is to it.