Nested class lifecycle in JUnit - Test Execution Trace

Test Overview

This test demonstrates the lifecycle of nested test classes in JUnit 5. It verifies that the outer and inner test classes run their setup and teardown methods in the correct order, and that test methods inside the nested class execute successfully.

Test Code - JUnit 5

JUnit

import org.junit.jupiter.api.*;

@TestInstance(TestInstance.Lifecycle.PER_CLASS)
public class OuterTest {

    @BeforeAll
    void beforeAllOuter() {
        System.out.println("Outer beforeAll");
    }

    @BeforeEach
    void beforeEachOuter() {
        System.out.println("Outer beforeEach");
    }

    @Test
    void outerTest() {
        System.out.println("Outer test running");
        Assertions.assertTrue(true);
    }

    @Nested
    @TestInstance(TestInstance.Lifecycle.PER_CLASS)
    class InnerTest {

        @BeforeAll
        void beforeAllInner() {
            System.out.println("Inner beforeAll");
        }

        @BeforeEach
        void beforeEachInner() {
            System.out.println("Inner beforeEach");
        }

        @Test
        void innerTest() {
            System.out.println("Inner test running");
            Assertions.assertEquals(2, 1 + 1);
        }

        @AfterEach
        void afterEachInner() {
            System.out.println("Inner afterEach");
        }

        @AfterAll
        void afterAllInner() {
            System.out.println("Inner afterAll");
        }
    }

    @AfterEach
    void afterEachOuter() {
        System.out.println("Outer afterEach");
    }

    @AfterAll
    void afterAllOuter() {
        System.out.println("Outer afterAll");
    }
}

Execution Trace - 14 Steps

Step	Action	System State	Assertion	Result
1	Test starts - JUnit initializes OuterTest class	JUnit test runner ready to execute OuterTest	-	PASS
2	Runs OuterTest @BeforeAll method	Outer beforeAll printed	-	PASS
3	Runs OuterTest @BeforeEach method before outerTest	Outer beforeEach printed	-	PASS
4	Runs OuterTest test method outerTest	Outer test running printed	assertTrue(true) passes	PASS
5	Runs OuterTest @AfterEach method after outerTest	Outer afterEach printed	-	PASS
6	JUnit initializes InnerTest nested class	Ready to execute InnerTest	-	PASS
7	Runs InnerTest @BeforeAll method	Inner beforeAll printed	-	PASS
8	Runs OuterTest @BeforeEach method before innerTest	Outer beforeEach printed	-	PASS
9	Runs InnerTest @BeforeEach method before innerTest	Inner beforeEach printed	-	PASS
10	Runs InnerTest test method innerTest	Inner test running printed	assertEquals(2, 1 + 1) passes	PASS
11	Runs InnerTest @AfterEach method after innerTest	Inner afterEach printed	-	PASS
12	Runs OuterTest @AfterEach method after innerTest	Outer afterEach printed	-	PASS
13	Runs InnerTest @AfterAll method after all inner tests	Inner afterAll printed	-	PASS
14	Runs OuterTest @AfterAll method after all tests	Outer afterAll printed	-	PASS

Failure Scenario

Failing Condition: InnerTest @BeforeAll method throws an exception

Execution Trace Quiz - 3 Questions

Which method runs first when executing the OuterTest class?

A OuterTest @BeforeEach

B OuterTest @BeforeAll

C InnerTest @BeforeAll

D InnerTest @BeforeEach

Key Result

Using nested test classes in JUnit 5 allows organizing related tests with their own lifecycle methods. Outer class lifecycle methods run around all tests, while nested class lifecycle methods run only for their tests, helping keep setup and teardown clear and scoped.