Kotlin - JUnit and Kotlin Test

JUnit and Kotlin Test

JUnit and Kotlin Test are libraries that you can use to unit test your code so that you can always have a safety net.

Add the JUnit library 

you can add these lines to your build.gradle file:

dependencies{

testimplementation 'org.junit.jupiter:jupiter:junit-jupiter-api:5.3.1'
testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.3.31'
test{useJUnitPlatform}

}

So let me show you how to write the JUnit with Kotlin. Let's create a class :

class Totaller(var total : Int =0)
{
  fun add (num: Int) : Int{
       total+ = num
   return total
  }
}

Create a JUnit test class like below :

class Totaller(var total : Int =0)

{

  fun add (num: Int) : Int{

       total+ = num

   return total

  }

}

TotallerTest:

import org.junit.jupiter.api.Assertions.*

import org.junit.jupiter.api.Test

class TotallerTest

{

 @Test

 fun shouldBeAbleToAdd3And4()

 {

   val totaller = Totaller()

   

   assertEquals(3 , totaller.add(3))

   assertEquals(3 , totaller.add(4))

   assertEquals(3 , totaller.total)

 }

}

Points to take a note on:

1) We are using code from the JUnit packages so we need to import them.

2)The TotallerTest class is used to test Totaller

3)@Test is an annotation that marks the following function as a test.

4)Tests are made up of actions and assertions.

5)Actions are a piece of code that does stuff while assertions are pieces of code that check stuff.

Now We will use the KotlinTest :

The KotlinTest library has been designed to use the full bread of the Kotlin language to write tests in a more expressive way.

KotlinTest is pretty vast and it allows you to write tests in many different styles but here is one way of writing a KotlinTest version of the JUnit code.

import io.kotlintest.shouldBe

imnport io.kotlintest.specs.StringSpec

class AnotherTotallerTest :StringSpec({

"Should be able to add 3 and 4  - and it must not go wrong"{

   

    val totaller = TotallerTest()

totaller.add(3) shouldBe 3

totaller.add(4) shouldBe 7

totaller.total shouldBe 7

  

}

Points to take a note on:

This is String Specification or StringSpec style.

Now we will use rows to test against sets of data

import io.kotlintest.data.forall

import io.kotlintest.shoudBe

import io.kotlintest.specs.StringSpec

import io.kotlintest.tables.rows

class AnotherTotallerTest :StringSpec({

"Should be able to add 3 and 4  - and it must not go wrong"{

   

    val totaller = TotallerTest()

totaller.add(3) shouldBe 3

totaller.add(4) shouldBe 7

totaller.total shouldBe 7

  

}

"should be able to add lots of different numbers"{

forall(

         row(1,2,3),

row(19,47,66),

row(11,21,32)

){ x,y,expectedTotal - >

val totaller = TotallerTest(x)

totaller.add(y) shouldBe expectedTotal

}

}

})  

Points to take a note on:

• Run test in parallel
• Create tests with generated properties
• Enable/disable tests dynamically. you may, for example, want some test to run only on Linux and others to run on Mac.
• Put tests in groups.