1. Why we test

[THEORY]

[PREDICT]

Read the code carefully before you run it.

prediction.kt

fun finalPriceInCents(pricePerItemInCents: Int, discountFromQuantity: Int, quantity: Int): Int {
    return if (quantity >= discountFromQuantity) pricePerItemInCents * quantity * 9 / 10
           else pricePerItemInCents * quantity
}

fun main() {
    println(finalPriceInCents(1000, 5, 5))
    println(finalPriceInCents(1000, 5, 4))
}

What do the two println calls print (price in cents)?

[TASK]

The function getDiscountTier should give a 5% discount from 10 items and a 10% discount from 50 items, everything below gets no discount. Run the code and compare each output with the expected result in the comment behind it. Several of the three calls do not match the specification — find the common root cause and correct it so that all three cases are right.

task.kt

fun getDiscountTier(quantity: Int): String { return when { quantity > 50 -> "10% discount" quantity > 10 -> "5% discount" else -> "no discount" } } fun main() { println(getDiscountTier(10)) // expected: "5% discount" println(getDiscountTier(50)) // expected: "10% discount" println(getDiscountTier(9)) // expected: "no discount" }

Before you get a hint: what have you tried, and where exactly are you stuck?

[COMPREHENSION CHECK]

1. Which testing principle does the prediction example above show most clearly?

Two tested quantities are enough to show that a discount rule works for every quantity A larger number of test cases lowers the risk of bugs, no matter which values they use Boundary checks matter for safety-critical software, not for everyday shop logic like discounts Boundary values, where a condition flips from true to false, are a common source of bugs

2. What does the principle 'Testing shows the presence of defects, not their absence' state?

A passed test says nothing about the code, only a failed test provides any information Once every line of code has run in at least one test, the code is proven to be free of defects A passed test only shows that no defect was found for the cases that were actually checked A passed test proves there are no defects, a failed test only suggests that one might exist