JUnit 4 vs JUnit 5 (Jupiter) differences - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

JUnit 4 vs JUnit 5: Annotation Differences

Which annotation is used in JUnit 5 to replace JUnit 4's @Before annotation for setup methods?

A @Init

B @BeforeAll

C @BeforeEach

D @Setup

💡 Hint

JUnit 5 renamed lifecycle annotations to be more descriptive per test method or all tests.

JUnit 4 uses @Before to run setup before each test method. JUnit 5 replaces this with @BeforeEach to clarify it runs before each test.

❓ Predict Output

intermediate

JUnit 5 Test Execution Result

What will be the test execution result of this JUnit 5 test class?

JUnit

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;

public class SampleTest {
    @Test
    void testSum() {
        assertEquals(5, 2 + 3);
    }
}

A Test fails with AssertionError

B Test passes

C Compilation error due to missing @RunWith

D Test ignored

💡 Hint

JUnit 5 does not require @RunWith for basic tests.

The test method asserts 2 + 3 equals 5, which is true, so the test passes.

❓ assertion

advanced

Correct Assertion for Exception Testing in JUnit 5

Which assertion correctly tests that a method throws NullPointerException in JUnit 5?

JUnit

public void methodThatThrows() {
    throw new NullPointerException();
}

A assertException(NullPointerException.class, () -> methodThatThrows());

B @Test(expected = NullPointerException.class) public void test() { methodThatThrows(); }

C assertThatThrownBy(() -> methodThatThrows()).isInstanceOf(NullPointerException.class);

D assertThrows(NullPointerException.class, () -> methodThatThrows());

💡 Hint

JUnit 5 uses assertThrows for exception testing.

JUnit 5 uses assertThrows to check exceptions. Option D is JUnit 4 style and won't compile in JUnit 5 without vintage engine.

❓ framework

advanced

JUnit 5 Modular Architecture

Which statement best describes JUnit 5's architecture compared to JUnit 4?

A JUnit 5 is composed of three modules: Jupiter, Vintage, and Platform.

B JUnit 5 uses the same runner mechanism as JUnit 4.

C JUnit 5 requires no dependencies and runs standalone.

D JUnit 5 is a single monolithic jar replacing JUnit 4.

💡 Hint

JUnit 5 separates concerns into modules for flexibility.

JUnit 5 consists of the Jupiter module for new tests, Vintage for backward compatibility, and Platform for launching tests.

🔧 Debug

expert

JUnit 5 Test Not Executing

Given this JUnit 5 test class, why does the test method not run?

JUnit

import org.junit.jupiter.api.Test;

public class MyTest {
    public void testMethod() {
        System.out.println("Running test");
    }
}

A The test method is missing the @Test annotation.

B The test method must be static.

C The class must extend a JUnit 5 base test class.

D JUnit 5 requires test methods to be public static void.

💡 Hint

JUnit 5 identifies tests by annotations, not method names.

JUnit 5 runs methods annotated with @Test. Without it, the method is ignored.

Practice

1. Which of the following is a key difference between JUnit 4 and JUnit 5 regarding test method visibility?

easy

A. JUnit 4 requires test methods to be public, but JUnit 5 does not.

B. JUnit 5 requires test methods to be public, but JUnit 4 does not.

C. Both JUnit 4 and JUnit 5 require test methods to be private.

D. Neither JUnit 4 nor JUnit 5 require any specific visibility for test methods.

Solution

1. Step 1: Understand JUnit 4 test method visibility

   JUnit 4 requires test methods to be declared as public for the framework to recognize and run them.

2. Step 2: Understand JUnit 5 test method visibility

   JUnit 5 allows test methods to have any visibility, including package-private, making it more flexible.

3. Final Answer:

   JUnit 4 requires test methods to be public, but JUnit 5 does not. -> Option A

4. Quick Check:

   JUnit 4 public test methods = true [OK]

Hint: Remember: JUnit 4 needs public tests; JUnit 5 is more relaxed [OK]

Common Mistakes:

• Thinking JUnit 5 also requires public test methods
• Assuming both versions have the same visibility rules
• Confusing private and public requirements

2. Which annotation replaces @Before from JUnit 4 in JUnit 5?

easy

A. @Init

B. @BeforeAll

C. @Setup

D. @BeforeEach

Solution

1. Step 1: Identify JUnit 4 setup annotation

   JUnit 4 uses @Before to run code before each test method.

2. Step 2: Identify JUnit 5 equivalent annotation

   JUnit 5 replaces @Before with @BeforeEach to clarify it runs before each test method.

3. Final Answer:

   @BeforeEach -> Option D

4. Quick Check:

   @Before in JUnit 4 = @BeforeEach in JUnit 5 [OK]

Hint: Think "Each" means before every test, replacing @Before [OK]

Common Mistakes:

• Choosing @BeforeAll which runs once before all tests
• Using non-existent annotations like @Setup or @Init
• Confusing @BeforeEach with @AfterEach

3. Consider this JUnit 5 test class snippet:

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;

class CalculatorTest {
  @Test
  void addTest() {
    int result = 2 + 3;
    assertEquals(5, result);
  }
}

What will be the test result when running this test?

medium

A. Test passes successfully

B. Test fails with assertion error

C. Compilation error due to missing public modifier

D. Runtime error due to missing @BeforeEach

Solution

1. Step 1: Check method visibility in JUnit 5

   The test method is package-private (no modifier), which is allowed in JUnit 5.

2. Step 2: Verify assertion correctness

   The assertion compares 5 and result (2+3=5), so it matches and passes.

3. Final Answer:

   Test passes successfully -> Option A

4. Quick Check:

   2 + 3 = 5, assertion true [OK]

Hint: JUnit 5 allows non-public tests; 2+3=5 means pass [OK]

Common Mistakes:

• Assuming test methods must be public in JUnit 5
• Thinking missing @BeforeEach causes failure here
• Confusing assertion order causing failure

4. Given this JUnit 4 test snippet:

import org.junit.Before;
import org.junit.Test;

public class SampleTest {
  @Before
  public void setup() {
    System.out.println("Setup");
  }

  @Test
  void testMethod() {
    System.out.println("Test");
  }
}

What is the main issue when running this test?

medium

A. No issues; test runs and prints both lines

B. The test method must be public in JUnit 4

C. The setup method must be static

D. The @Before annotation is not recognized in JUnit 4

Solution

1. Step 1: Check test method visibility requirement in JUnit 4

   JUnit 4 requires test methods to be public, but here testMethod() has default (package-private) visibility.

2. Step 2: Verify @Before method correctness

   The setup() method is public and correctly annotated, so no issue there.

3. Final Answer:

   The test method must be public in JUnit 4 -> Option B

4. Quick Check:

   JUnit 4 test methods must be public [OK]

Hint: JUnit 4 needs public test methods; check method modifiers [OK]

Common Mistakes:

• Thinking @Before is invalid in JUnit 4
• Assuming setup must be static
• Believing test runs despite non-public test method

5. You want to migrate a JUnit 4 test class to JUnit 5. Which of these changes is NOT required?

hard

A. Change import statements to JUnit Jupiter packages

B. Replace @Before with @BeforeEach

C. Make all test methods public

D. Replace @Test import to JUnit Jupiter's @Test

Solution

1. Step 1: Identify visibility requirements in JUnit 5

   JUnit 5 does not require test methods to be public; package-private is allowed.

2. Step 2: Check other migration steps

   Replacing @Before with @BeforeEach and updating imports to Jupiter packages are required for migration.

3. Final Answer:

   Make all test methods public -> Option C

4. Quick Check:

   JUnit 5 relaxes method visibility rules [OK]

Hint: JUnit 5 allows non-public tests; no need to change visibility [OK]

Common Mistakes:

• Thinking test methods must be public in JUnit 5
• Forgetting to update import statements
• Missing @Before to @BeforeEach replacement