Property-based testing concept in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a property test function using Kotest.

Kotlin

fun testAddition() = property({ forAll<Int, Int> { a, b -> (a + b) [1] (b + a) } })

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A==

B=

C!=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using assignment operator '=' instead of equality '=='

Using inequality '!=' which would invert the test logic

The property test checks if addition is commutative by asserting a + b == b + a.

2fill in blank

medium

Complete the code to generate random strings for property testing.

Kotlin

val stringGen = Gen.[1](5..10)

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Alist

Bint

Cboolean

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using Gen.int or Gen.boolean which generate numbers or booleans, not strings

Using Gen.list which generates lists, not strings

We use Gen.string to generate random strings of length between 5 and 10.

3fill in blank

hard

Fix the error in the property test that checks list reversal.

Kotlin

property({ forAll<List<Int>> { list -> list.reversed().reversed() [1] list } })

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A!=

B=

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using assignment '=' instead of equality '=='

Using inequality '!=' which would fail the test

The test asserts that reversing a list twice returns the original list, so we use == to check equality.

4fill in blank

hard

Fill both blanks to create a property test that checks if sorting a list keeps its size unchanged.

Kotlin

property({ forAll<List<Int>> { list -> list.sorted().[1] list.size && list.size [2] list.sorted().size } })

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Asize ==

B==

C!=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using inequality '!=' which would fail the test

Using '<' which is incorrect for size comparison

The test checks that the size of the sorted list equals the original list size, so we use size == and == operators.

5fill in blank

hard

Fill all three blanks to create a property test that checks if concatenating two strings has length equal to the sum of their lengths.

Kotlin

property({ forAll<String, String> { s1, s2 -> (s1 + s2).[1] == s1.[2] + s2.[3] } })

Drag options to blanks, or click blank then click option'

Alength

Bcount

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using count or size which are not properties of String in Kotlin

Mixing different properties for length comparison

The property test checks that the length of the concatenated string equals the sum of the lengths of the two strings. The correct property to use is length.