Why parameterization reduces test duplication in JUnit - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to use the correct annotation for parameterized tests in JUnit.

JUnit

@[1]
public void testSum(int a, int b, int expected) {
    assertEquals(expected, a + b);
}

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AParameterizedTest

BAfterEach

CTest

DBeforeEach

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Test instead of @ParameterizedTest causes the test to run only once.

Using lifecycle annotations like @BeforeEach instead of test annotations.

The @ParameterizedTest annotation tells JUnit to run the test multiple times with different parameters, reducing duplication.

2fill in blank

medium

Complete the code to provide multiple sets of parameters using the correct source annotation.

JUnit

@ParameterizedTest
@[1]({"1, 2, 3", "3, 4, 7", "5, 6, 11"})
public void testSum(int a, int b, int expected) {
    assertEquals(expected, a + b);
}

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AValueSource

BEnumSource

CMethodSource

DCsvSource

Attempts:

3 left

💡 Hint

Common Mistakes

Using @ValueSource which supports only single parameter arrays.

Using @MethodSource without defining a method.

@CsvSource allows passing multiple comma-separated values as parameters to the test method, enabling parameterization.

3fill in blank

hard

Fix the error in the parameterized test method signature to match the parameters provided.

JUnit

@ParameterizedTest
@CsvSource({"2, 3, 5", "4, 5, 9"})
public void testSum([1]) {
    assertEquals(expected, a + b);
}

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Aint a, int b, int expected

Bint a, int b

CString a, String b, String expected

Dint expected

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the expected parameter causes compilation errors.

Using wrong parameter types like String instead of int.

The test method must have parameters matching the number and types of values in each CSV line: int a, int b, int expected.

4fill in blank

hard

Fill both blanks to correctly import and use the assertion method in JUnit 5.

JUnit

import static org.junit.jupiter.api.Assertions.[1];

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

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AassertEquals

BassertTrue

CassertFalse

DassertNull

Attempts:

3 left

💡 Hint

Common Mistakes

Using assertTrue or assertFalse when checking equality.

Forgetting to import the assertion method.

assertEquals is the correct assertion to check if two values are equal in JUnit 5.

5fill in blank

hard

Fill all three blanks to complete a parameterized test that uses a method source for input data.

JUnit

@ParameterizedTest
@MethodSource("[1]")
public void testMultiply(int a, int b, int expected) {
    assertEquals([2], a * b);
}

static Stream<Arguments> [3]() {
    return Stream.of(
        Arguments.of(2, 3, 6),
        Arguments.of(4, 5, 20),
        Arguments.of(6, 7, 42)
    );
}

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AmultiplyData

Bexpected

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching method source name causes runtime errors.

Using wrong variable names in assertion.

The method source name must match the string in @MethodSource. The assertion compares expected with the product. The method providing data is named multiplyData.