Property-based testing concept in Kotlin - Mini Project: Build & Apply

Property-based Testing Concept in Kotlin

📖 Scenario: You are working on a simple Kotlin function that reverses strings. You want to make sure it works correctly for many cases, not just a few examples.

🎯 Goal: Build a property-based test that checks if reversing a string twice returns the original string.

📋 What You'll Learn

Create a function called reverseString that takes a String and returns its reverse.

Create a property test function called testDoubleReverse that checks the property: reversing twice returns the original string.

Use a list of sample strings to test the property.

Print "All tests passed!" if all tests succeed.

💡 Why This Matters

🌍 Real World

Property-based testing helps catch bugs by checking that your code works for many inputs, not just a few examples.

💼 Career

Understanding property-based testing is useful for software developers to write more reliable and robust code.

1

Create the reverseString function

Write a Kotlin function called reverseString that takes a String parameter named input and returns the reversed string using reversed().

Kotlin

// Write the function reverseString here

Need a hint?

Use the built-in reversed() function on the input string.

2

Create a list of sample strings

Create a val named sampleStrings and assign it a list of strings: "hello", "world", "kotlin", "property", "test".

Kotlin

fun reverseString(input: String): String {
    return input.reversed()
}

// Create sampleStrings list here

Need a hint?

Use listOf to create the list with the exact strings.

3

Write the property test function testDoubleReverse

Write a function called testDoubleReverse with no parameters. Inside, use a for loop with variable str to iterate over sampleStrings. For each str, check if reverseString(reverseString(str)) == str. If any check fails, print "Test failed for: " + str and return false. If all pass, return true.

Kotlin

fun reverseString(input: String): String {
    return input.reversed()
}

val sampleStrings = listOf("hello", "world", "kotlin", "property", "test")

// Write testDoubleReverse function here

Need a hint?

Use a for loop and if statement to check the property for each string.

4

Run the test and print the result

Call the function testDoubleReverse() and if it returns true, print "All tests passed!".

Kotlin

fun reverseString(input: String): String {
    return input.reversed()
}

val sampleStrings = listOf("hello", "world", "kotlin", "property", "test")

fun testDoubleReverse(): Boolean {
    for (str in sampleStrings) {
        if (reverseString(reverseString(str)) != str) {
            println("Test failed for: $str")
            return false
        }
    }
    return true
}

// Call testDoubleReverse and print result

Need a hint?

Use an if statement to check the return value and print the success message.