How to test a function in Kotlin with Junit

Issue

I write a program in Kotlin. The program is working fine, but I only test the function with running the program. I think I know what the problem is, but I don't know, how to modiy the test. Thanks in advance!

class Dice {
var firstDice = 1
var secondDice = 1
var thirdDice = 3
var fourthDice = 2
var fifthDice = 2
val dices: MutableList<Int> = ArrayList()

fun throwDices() {
    firstDice = Random.nextInt(1,7)
    dices.add(firstDice)
    println("Eldobtad a kockákat, az első kocka értéke: $firstDice")
    secondDice = Random.nextInt(1,7)
    dices.add(secondDice)
    println("A második kocka értéke: $secondDice")
    thirdDice = Random.nextInt(1,7)
    dices.add(thirdDice)
    println("A harmadik kocka értéke: $thirdDice")
    fourthDice = Random.nextInt(1,7)
    dices.add(fourthDice)
    println("A negyedik kocka értéke: $fourthDice")
    fifthDice = Random.nextInt(1,7)
    dices.add(fifthDice)
    println("Az ötödik kocka értéke: $fifthDice")
    dices.sort()
    println(dices)
}

fun winningCheck() :Int {
    if(dices[0] == dices[1] && dices[0] == dices[2] && dices[0] == dices[3] && dices[0] == dices[4] ) {
        return 15
    }
    else if(dices[0] == dices[1] && dices[0] == dices[2] && dices[0] == dices[3]) {
        return  9
    }
    else if (dices[0] == dices[1] && dices[0] == dices[2] && dices[3] == dices[4]) {
        return 5
    }
    else if(dices[0] == dices[1] && dices[0] == dices[2] || dices[1] == dices[2] && dices[1] == dices[3] ||
            dices[2] == dices[3] && dices[2] == dices[4]) {
        return 3
    }
    else if(dices[0] == dices[1] && dices[2] == dices[3] ||
            dices[1] == dices[2] && dices[3] == dices[4] ||
            dices[0] == dices[1] && dices[3] == dices[4]) {
        return  2
    }else if (dices[0] == dices[1] || dices[1] == dices[2] || dices[2] == dices[3] || dices[3] == dices[4]) {
        return 1
    }
    else
        return 0
}

}

This is the class, I want to test, and here is the testing code:

class DiceTest {

private val dice = Dice()
private val dices: MutableList<Int> = ArrayList()

@Before
fun init() {
    dice.firstDice = 1
    dice.secondDice = 1
    dice.thirdDice= 1
    dice.fourthDice = 1
    dice.fifthDice = 1

    dices.add(dice.firstDice)
    dices.add(dice.secondDice)
    dices.add(dice.thirdDice)
    dices.add(dice.fourthDice)
    dices.add(dice.fifthDice)
}

@Test
fun checkingFiveOfAKind () {
    assertEquals(15,dice.winningCheck())
}

And here is the error code:

Solution

I think your example could be simplified to ask, why does't this code work:

@Test
fun checkingFiveOfAKind() {
    val dices: MutableList<Int> = ArrayList()
    dices.add(1)
    dices.add(1)
    dices.add(1)
    dices.add(1)
    dices.add(1)
    
    val anotherDices: MutableList<Int> = ArrayList()

    val result :Int
    if(anotherDices[0] == anotherDices[1] 
       && anotherDices[0] == anotherDices[2] 
       && anotherDices[0] == anotherDices[3] 
       && anotherDices[0] == anotherDices[4] ) {
       result = 15
    } else {
       result = 0
    }
 
    assertEquals(15, result)
}

But this code does work:

@Test
fun checkingFiveOfAKind() {
    val dices: MutableList<Int> = ArrayList()
    dices.add(1)
    dices.add(1)
    dices.add(1)
    dices.add(1)
    dices.add(1)
    
    val result :Int
    if(dices[0] == dices[1] 
       && dices[0] == dices[2] 
       && dices[0] == dices[3] 
       && dices[0] == dices[4] ) {
       result = 15
    } else {
       result = 0
    }
 
    assertEquals(15, result)
}

---

Or written another way:

You are adding your dice rolls to a variable called dices but this is a declared in your test, it is not the variable you are using inside your Dice class, that is another List.

You may be able to fix your test like this:

class DiceTest {

private val dice = Dice()

@Before
fun init() {
    dice.firstDice = 1
    dice.secondDice = 1
    dice.thirdDice= 1
    dice.fourthDice = 1
    dice.fifthDice = 1

    dice.dices.add(dice.firstDice)
    dice.dices.add(dice.secondDice)
    dice.dices.add(dice.thirdDice)
    dice.dices.add(dice.fourthDice)
    dice.dices.add(dice.fifthDice)
}

@Test
fun checkingFiveOfAKind () {
    assertEquals(15, dice.winningCheck())
}

Answered By - Blundell