Test fixtures and lifecycle in Kotlin - Mini Project: Build & Apply

Test fixtures and lifecycle

📖 Scenario: You are writing simple tests for a calculator app. You want to set up a calculator object before each test and clean up after each test.

🎯 Goal: Learn how to use test fixtures and lifecycle methods in Kotlin tests to prepare and clean up test data.

📋 What You'll Learn

Create a Calculator class instance as a test fixture

Use @BeforeEach to initialize the Calculator before each test

Use @AfterEach to reset the Calculator after each test

Write a simple test method that uses the Calculator

💡 Why This Matters

🌍 Real World

Test fixtures and lifecycle methods help prepare and clean up data for automated tests in real apps.

💼 Career

Understanding test lifecycle is essential for writing reliable unit tests in Kotlin development jobs.

1

Create Calculator class and test fixture variable

Create a Kotlin class called Calculator with a method add(a: Int, b: Int): Int that returns the sum of a and b. Then create a test class called CalculatorTest and declare a variable calculator of type Calculator? initialized to null.

Kotlin

class Calculator {
    // Your code here
}

class CalculatorTest {
    var calculator: Calculator? = null
    // Your code here
}

Need a hint?

Define the Calculator class with an add method. Declare a nullable Calculator variable in the test class.

2

Initialize Calculator before each test

In the CalculatorTest class, add a method annotated with @BeforeEach called setup that creates a new Calculator instance and assigns it to the calculator variable.

Kotlin

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

class CalculatorTest {
    var calculator: Calculator? = null

    // Add a @BeforeEach method called setup to initialize calculator
    // Your code here
}

Need a hint?

Use @BeforeEach annotation and assign a new Calculator to calculator inside setup.

3

Reset Calculator after each test

In the CalculatorTest class, add a method annotated with @AfterEach called tearDown that sets the calculator variable to null.

Kotlin

import org.junit.jupiter.api.BeforeEach

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

class CalculatorTest {
    var calculator: Calculator? = null

    @BeforeEach
    fun setup() {
        calculator = Calculator()
    }

    // Add a @AfterEach method called tearDown to reset calculator
    // Your code here
}

Need a hint?

Use @AfterEach annotation and set calculator to null inside tearDown.

4

Write a test using the fixture

In the CalculatorTest class, add a test method annotated with @Test called testAdd that uses the calculator variable to call add(2, 3) and prints the result.

Kotlin

import org.junit.jupiter.api.BeforeEach
import org.junit.jupiter.api.AfterEach
import org.junit.jupiter.api.Test

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

class CalculatorTest {
    var calculator: Calculator? = null

    @BeforeEach
    fun setup() {
        calculator = Calculator()
    }

    @AfterEach
    fun tearDown() {
        calculator = null
    }

    // Add a @Test method called testAdd that prints calculator.add(2, 3)
    // Your code here
}

Need a hint?

Use @Test annotation and print the result of calculator?.add(2, 3).