Execution order of lifecycle methods in JUnit - Test Execution Trace

Test Overview

This test demonstrates the order in which JUnit lifecycle methods run. It verifies that methods annotated with @BeforeAll run once before all tests, @BeforeEach runs before each test, @Test methods run as tests, @AfterEach runs after each test, and @AfterAll runs once after all tests.

Test Code - JUnit 5

JUnit

import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertTrue;

public class LifecycleOrderTest {

    static StringBuilder log = new StringBuilder();

    @BeforeAll
    static void beforeAll() {
        log.append("beforeAll-");
    }

    @BeforeEach
    void beforeEach() {
        log.append("beforeEach-");
    }

    @Test
    void testOne() {
        log.append("testOne-");
        assertTrue(true);
    }

    @Test
    void testTwo() {
        log.append("testTwo-");
        assertTrue(true);
    }

    @AfterEach
    void afterEach() {
        log.append("afterEach-");
    }

    @AfterAll
    static void afterAll() {
        log.append("afterAll");
        // Verify the full expected order
        String expected = "beforeAll-beforeEach-testOne-afterEach-beforeEach-testTwo-afterEach-afterAll";
        assertTrue(log.toString().equals(expected));
    }
}

Execution Trace - 8 Steps

Step	Action	System State	Assertion	Result
1	JUnit framework calls @BeforeAll static method	No tests run yet, log is empty	—	PASS
2	JUnit runs first test: calls @BeforeEach method	log contains 'beforeAll-'	—	PASS
3	JUnit runs first test method testOne()	log contains 'beforeAll-beforeEach-'	assertTrue(true) in testOne	PASS
4	JUnit calls @AfterEach method after testOne	log contains 'beforeAll-beforeEach-testOne-'	—	PASS
5	JUnit runs second test: calls @BeforeEach method	log contains 'beforeAll-beforeEach-testOne-afterEach-'	—	PASS
6	JUnit runs second test method testTwo()	log contains 'beforeAll-beforeEach-testOne-afterEach-beforeEach-'	assertTrue(true) in testTwo	PASS
7	JUnit calls @AfterEach method after testTwo	log contains 'beforeAll-beforeEach-testOne-afterEach-beforeEach-testTwo-'	—	PASS
8	JUnit calls @AfterAll static method after all tests	log contains 'beforeAll-beforeEach-testOne-afterEach-beforeEach-testTwo-afterEach-'	assertTrue(log.toString().equals(expected))	PASS

Failure Scenario

Failing Condition: The lifecycle methods do not run in the expected order or a test assertion fails

Execution Trace Quiz - 3 Questions

Which lifecycle method runs only once before all tests?

A @AfterEach

B @BeforeAll

C @BeforeEach

D @AfterAll

Key Result

Use lifecycle methods to set up and clean up tests in a clear order. Verifying their execution order helps ensure tests run predictably and resources are managed properly.

Practice

1. In JUnit 5, which lifecycle method runs exactly once before any test methods in the class?

easy

A. @AfterAll

B. @BeforeEach

C. @AfterEach

D. @BeforeAll

Solution

1. Step 1: Understand lifecycle annotations

   @BeforeAll is designed to run once before all tests in the class.

2. Step 2: Compare with other annotations

   @BeforeEach runs before each test, @AfterEach after each test, and @AfterAll once after all tests.

3. Final Answer:

   @BeforeAll -> Option D

4. Quick Check:

   @BeforeAll runs once before all tests [OK]

Hint: Remember: All = once before all tests [OK]

Common Mistakes:

• Confusing @BeforeEach with @BeforeAll
• Thinking @AfterAll runs before tests
• Mixing up @AfterEach and @BeforeEach

2. Which of the following is the correct syntax to define a method that runs after each test in JUnit 5?

easy

A. @AfterEach
void cleanup() {}

B. @AfterAll
void cleanup() {}

C. @BeforeEach
void cleanup() {}

D. @BeforeAll
void cleanup() {}

Solution

1. Step 1: Identify the annotation for after each test

   @AfterEach is the annotation that runs a method after every test method.

2. Step 2: Check method syntax

   The method should be void and can have any name, here 'cleanup()' is valid.

3. Final Answer:

   @AfterEach void cleanup() {} -> Option A

4. Quick Check:

   @AfterEach runs after each test method [OK]

Hint: AfterEach means after every single test method [OK]

Common Mistakes:

• Using @AfterAll instead of @AfterEach
• Confusing @BeforeEach with @AfterEach
• Missing void return type

3. Consider the following JUnit 5 test class:

@BeforeAll
static void initAll() { System.out.println("InitAll"); }
@BeforeEach
void init() { System.out.println("Init"); }
@Test
void testOne() { System.out.println("TestOne"); }
@Test
void testTwo() { System.out.println("TestTwo"); }
@AfterEach
void tearDown() { System.out.println("TearDown"); }
@AfterAll
static void tearDownAll() { System.out.println("TearDownAll"); }

What is the correct order of printed lines when running this test class?

medium

A. InitAll, Init, TestOne, TearDown, Init, TestTwo, TearDown, TearDownAll

B. Init, InitAll, TestOne, TearDown, TestTwo, Init, TearDownAll

C. InitAll, Init, TestOne, Init, TestTwo, TearDown, TearDownAll, TearDown

D. InitAll, TestOne, Init, TearDown, Init, TestTwo, TearDown, TearDownAll

Solution

1. Step 1: Understand lifecycle method order

   @BeforeAll runs once before all tests, then for each test @BeforeEach runs, test runs, then @AfterEach runs. Finally, @AfterAll runs once after all tests.

2. Step 2: Apply to given methods

   Output order: InitAll (once), then for testOne: Init, TestOne, TearDown; for testTwo: Init, TestTwo, TearDown; finally TearDownAll.

3. Final Answer:

   InitAll, Init, TestOne, TearDown, Init, TestTwo, TearDown, TearDownAll -> Option A

4. Quick Check:

   BeforeAll once, BeforeEach-Test-AfterEach per test, AfterAll once [OK]

Hint: Remember: BeforeAll/AfterAll once, BeforeEach/AfterEach per test [OK]

Common Mistakes:

• Mixing order of BeforeAll and BeforeEach
• Forgetting AfterEach runs after each test
• Placing AfterAll before AfterEach

4. Given the following JUnit 5 test class snippet, identify the error:

@BeforeAll
void setupAll() { System.out.println("Setup all"); }
@Test
void testMethod() { System.out.println("Test"); }

What is the problem with this code?

medium

A. @BeforeAll method must return boolean.

B. @BeforeAll method must be static.

C. @BeforeAll method cannot have a body.

D. @BeforeAll method must be private.

Solution

1. Step 1: Recall @BeforeAll requirements

   In JUnit 5, @BeforeAll methods must be static unless using a test instance lifecycle that allows non-static.

2. Step 2: Check method signature

   The method 'setupAll' is not static, which causes a runtime error or test failure.

3. Final Answer:

   @BeforeAll method must be static. -> Option B

4. Quick Check:

   @BeforeAll requires static method by default [OK]

Hint: @BeforeAll methods are static unless configured otherwise [OK]

Common Mistakes:

• Making @BeforeAll non-static without lifecycle config
• Assuming @BeforeAll can be private
• Thinking @BeforeAll must return a value

5. You want to open a database connection once before all tests and close it once after all tests in a JUnit 5 test class. You also want to reset some data before each test and clean up after each test. Which combination of lifecycle methods should you use?

hard

A. @BeforeAll for resetting data, @AfterAll for cleanup, @BeforeEach for opening connection, @AfterEach for closing connection

B. @BeforeEach for opening connection, @AfterEach for closing connection, @BeforeAll for resetting data, @AfterAll for cleanup

C. @BeforeAll for opening connection, @AfterAll for closing connection, @BeforeEach for resetting data, @AfterEach for cleanup

D. @BeforeEach for resetting data, @AfterEach for cleanup, @BeforeAll for opening connection, @AfterAll for closing connection

Solution

1. Step 1: Assign tasks to lifecycle methods

   Opening and closing the database connection should happen once, so use @BeforeAll and @AfterAll.

2. Step 2: Use per-test methods for data reset and cleanup

   Resetting data and cleaning up should happen before and after each test, so use @BeforeEach and @AfterEach.

3. Final Answer:

   @BeforeAll for opening connection, @AfterAll for closing connection, @BeforeEach for resetting data, @AfterEach for cleanup -> Option C

4. Quick Check:

   Once methods for setup/teardown, each methods for per-test tasks [OK]

Hint: Once = BeforeAll/AfterAll, each test = BeforeEach/AfterEach [OK]

Common Mistakes:

• Opening connection before each test unnecessarily
• Resetting data only once before all tests
• Closing connection after each test causing overhead