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

Practice - 5 Tasks

1fill in blank

easy

Complete the code to use the correct annotation for a test method in JUnit 5.

JUnit

@[1]
public void testAddition() {
    assertEquals(5, 2 + 3);
}

Drag options to blanks, or click blank then click option'

ATestMethod

BTest

CTestCase

DTestAnnotation

Attempts:

3 left

💡 Hint

Common Mistakes

Using @TestMethod which does not exist in JUnit 5.

Confusing with JUnit 4 imports.

In JUnit 5, the test method is annotated with @Test from the org.junit.jupiter.api package.

2fill in blank

medium

Complete the code to disable a test method in JUnit 5.

JUnit

@Test
@[1]
public void testFeature() {
    // test code
}

Drag options to blanks, or click blank then click option'

ADisabled

BIgnore

CSkip

DIgnoreTest

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Ignore which is from JUnit 4.

Using @Skip which does not exist.

In JUnit 5, to disable a test method, use the @Disabled annotation.

3fill in blank

hard

Fix the error in the JUnit 5 lifecycle method annotation for setup before all tests.

JUnit

@Before[1]
public static void initAll() {
    // initialization code
}

Drag options to blanks, or click blank then click option'

ASuite

BBeforeClass

CAllTests

DAll

Attempts:

3 left

💡 Hint

Common Mistakes

Using @BeforeClass which is from JUnit 4.

Using incorrect suffixes like 'Suite' or 'AllTests'.

In JUnit 5, the annotation for setup before all tests is @BeforeAll. It replaces JUnit 4's @BeforeClass.

4fill in blank

hard

Fill both blanks to correctly write a parameterized test in JUnit 5.

JUnit

@[1]
@[2](value = {"apple", "banana", "cherry"})
void testFruits(String fruit) {
    assertNotNull(fruit);
}

Drag options to blanks, or click blank then click option'

AParameterizedTest

BValueSource

CTest

DCsvSource

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Test instead of @ParameterizedTest.

Using @CsvSource when only simple values are needed.

In JUnit 5, parameterized tests use @ParameterizedTest and @ValueSource to supply values.

5fill in blank

hard

Fill all three blanks to write a JUnit 5 test method that asserts an exception is thrown.

JUnit

@Test
void testException() {
    Exception exception = assertThrows([1].class, () -> {
        throw new [2]("Error");
    });
    assertEquals("[3]", exception.getMessage());
}

Drag options to blanks, or click blank then click option'

AIllegalArgumentException

CError

DRuntimeException

Attempts:

3 left

💡 Hint

Common Mistakes

Using different exception classes in assertThrows and throw statement.

Mismatching the exception message string.

This test checks that an IllegalArgumentException is thrown with the message "Error".

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