A very hacky quick test thingy I wrote because I did not want to deal with libraries and imports but show people basic exercises. I'm pretty sure it'll fall apart on basic security.

hackyTest.kt

fun main() {
    println("Running stuff")
    
    case("5 + 10", weight=5) {
        var x = 15;
        x = x + 10
    	add(5, 10) == x
    }
    
    case("10 + 15") {
    	add(10, 15) == 25
    }
    
    case("Negative") {
    	add(10, -15) == -5
    }
    
    case("Zero", 10) {
    	add(10, 0) == 10
    }
}

fun case(name: String, weight: Int = 1, code: () -> Boolean): Boolean {
    val result = code()
    val resultDisplay = if (result) "PASSED" else "FAILED"
    println("TEST $name -> $resultDisplay") 

    return result
} 

fun add(a: Int, b: Int): Int {
    return a + b
}

Running stuff
TEST 5 + 10 -> FAILED
TEST 10 + 15 -> PASSED
TEST Negative -> PASSED
TEST Zero -> PASSED

MIT License