Why lifecycle hooks manage setup and teardown in JUnit - Automation Benefits in Action

Verify setup and teardown using JUnit lifecycle hooks

Preconditions (2)

Step 1: Create a test class CalculatorTest

Step 2: Use @BeforeEach to initialize a Calculator object before each test

Step 3: Write a test method testAdd that adds two numbers and asserts the result

Step 4: Write a test method testSubtract that subtracts two numbers and asserts the result

Step 5: Use @AfterEach to set the Calculator object to null after each test

Step 6: Run the tests and observe that setup runs before each test and teardown runs after each test

✅ Expected Result: Each test method runs with a fresh Calculator instance initialized by @BeforeEach, and after each test the Calculator reference is cleared by @AfterEach. Tests pass successfully.

Automation Requirements - JUnit 5

Assertions Needed:

Assert that add method returns correct sum

Assert that subtract method returns correct difference

Best Practices:

Use @BeforeEach for setup to ensure fresh test state

Use @AfterEach for cleanup to avoid side effects

Keep tests independent and repeatable

Automated Solution

JUnit

import static org.junit.jupiter.api.Assertions.*;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.Test;

class Calculator {
    int add(int a, int b) {
        return a + b;
    }
    int subtract(int a, int b) {
        return a - b;
    }
}

public class CalculatorTest {
    private Calculator calculator;

    @BeforeEach
    void setUp() {
        calculator = new Calculator();
    }

    @AfterEach
    void tearDown() {
        calculator = null;
    }

    @Test
    void testAdd() {
        int result = calculator.add(5, 3);
        assertEquals(8, result, "5 + 3 should equal 8");
    }

    @Test
    void testSubtract() {
        int result = calculator.subtract(10, 4);
        assertEquals(6, result, "10 - 4 should equal 6");
    }
}

The @BeforeEach method setUp() runs before each test method. It creates a new Calculator instance so each test starts fresh, avoiding shared state.

The @AfterEach method tearDown() runs after each test method. It clears the Calculator reference to help with cleanup and avoid side effects.

Each test method uses the Calculator instance to perform operations and asserts the expected results. This shows how lifecycle hooks manage setup and teardown to keep tests independent and reliable.

Common Mistakes - 3 Pitfalls

Initializing the Calculator object inside each test method instead of using @BeforeEach

Not cleaning up resources or resetting state in @AfterEach

Using @BeforeAll or @AfterAll for instance setup and teardown

Bonus Challenge

Now add a test method that verifies multiplication using the same setup and teardown lifecycle hooks.

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