@ParameterizedTest annotation in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the annotation for parameterized tests.

JUnit

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

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

ATest

BParameterizedTest

CBeforeEach

DAfterAll

Attempts:

3 left

💡 Hint

Common Mistakes

Importing @Test instead of @ParameterizedTest

Using annotations from JUnit 4

Forgetting to import the annotation

The @ParameterizedTest annotation is imported from org.junit.jupiter.api.ParameterizedTest.

2fill in blank

medium

Complete the code to supply string values for the parameterized test.

JUnit

@ParameterizedTest
@ValueSource(strings = {"apple", "banana", "cherry"})
void testFruits([1] fruit) {
    System.out.println(fruit);
}

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

AString

Bint

Cdouble

Dboolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using int or other types instead of String

Forgetting to match parameter type with @ValueSource type

The parameter type must match the type of values supplied by @ValueSource, which is String here.

3fill in blank

hard

Fix the error in the parameterized test method signature.

JUnit

@ParameterizedTest
@ValueSource(ints = {1, 2, 3})
void testNumbers([1] number) {
    assertTrue(number > 0);
}

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

AInteger

BString

Cint

Ddouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using String instead of int

Using wrapper Integer instead of primitive int

The parameter type must be int to match the ints array in @ValueSource.

4fill in blank

hard

Fill both blanks to create a parameterized test that checks if numbers are even.

JUnit

@ParameterizedTest
@ValueSource([1] = {2, 4, 6, 8})
void testEvenNumbers([2] number) {
    assertEquals(0, number % 2);
}

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

Aints

BString

Cint

Dstrings

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'strings' or 'String' for integer values

Mismatch between annotation and parameter types

The @ValueSource uses ints, so the parameter type must be int.

5fill in blank

hard

Fill all three blanks to create a parameterized test using @CsvSource with two parameters.

JUnit

@ParameterizedTest
@CsvSource({"apple, 1", "banana, 2", "cherry, 3"})
void testFruitCount([1] fruit, [2] count) {
    assertNotNull(fruit);
    assertTrue(count > [3]);
}

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

AString

Bint

C0

Ddouble

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong parameter types

Incorrect comparison value in assertion

The first parameter is a String, the second is an int, and the assertion checks count > 0.

Practice

1. What is the main purpose of the @ParameterizedTest annotation in JUnit?

easy

A. To group multiple test classes together

B. To skip a test method during execution

C. To mark a test method as the only one to run

D. To run the same test multiple times with different inputs

Solution

1. Step 1: Understand the role of @ParameterizedTest

   The annotation allows running one test method repeatedly with different input values.

2. Step 2: Compare with other options

   Skipping tests or grouping classes are done by other annotations, not @ParameterizedTest.

3. Final Answer:

   To run the same test multiple times with different inputs -> Option D

4. Quick Check:

   @ParameterizedTest = run test with many inputs [OK]

Hint: Think: same test, many inputs, no code repetition [OK]

Common Mistakes:

• Confusing @ParameterizedTest with @Test
• Thinking it skips tests
• Assuming it groups test classes

2. Which of the following is the correct way to provide integer values to a @ParameterizedTest using @ValueSource?

easy

A. @ValueSource(ints = {1, 2, 3})

B. @ValueSource(values = {1, 2, 3})

C. @ValueSource(strings = {1, 2, 3})

D. @ValueSource(numbers = {1, 2, 3})

Solution

1. Step 1: Recall @ValueSource syntax

   For integers, the correct attribute is 'ints', so @ValueSource(ints = {...}) is correct.

2. Step 2: Check other options

   'values', 'strings', and 'numbers' are invalid attributes for @ValueSource with integers.

3. Final Answer:

   @ValueSource(ints = {1, 2, 3}) -> Option A

4. Quick Check:

   Use 'ints' for integer arrays in @ValueSource [OK]

Hint: Use 'ints' attribute for integer arrays in @ValueSource [OK]

Common Mistakes:

• Using 'values' instead of 'ints'
• Using 'strings' for numbers
• Using unsupported attribute names

3. Given the following test method, what will be the output when running the parameterized test?

@ParameterizedTest
@ValueSource(strings = {"apple", "banana"})
void testLength(String fruit) {
    System.out.println(fruit.length());
}

medium

A. 5 and 6 printed on separate lines

B. 6 and 5 printed on separate lines

C. Only 5 printed once

D. Compilation error due to missing annotation

Solution

1. Step 1: Identify input values

   The test runs twice with inputs "apple" and "banana".

2. Step 2: Calculate string lengths

   "apple" length is 5, "banana" length is 6, so output prints 5 then 6 on separate lines.

3. Final Answer:

   5 and 6 printed on separate lines -> Option A

4. Quick Check:

   String lengths = 5, 6 [OK]

Hint: Check each input's length printed separately [OK]

Common Mistakes:

• Mixing order of outputs
• Expecting only one print
• Assuming compilation error

4. Identify the error in the following parameterized test code:

@ParameterizedTest
@ValueSource(ints = {1, 2, 3})
void testIsPositive(String number) {
    assertTrue(Integer.parseInt(number) > 0);
}

medium

A. Missing @Test annotation

B. Method parameter type should be int, not String

C. ValueSource should use strings instead of ints

D. assertTrue cannot be used in parameterized tests

Solution

1. Step 1: Check parameter type vs ValueSource

   @ValueSource provides ints, but method parameter is String, causing type mismatch.

2. Step 2: Correct parameter type

   Change method parameter to int to match input type and avoid parsing.

3. Final Answer:

   Method parameter type should be int, not String -> Option B

4. Quick Check:

   Parameter type must match @ValueSource type [OK]

Hint: Match method parameter type with @ValueSource data type [OK]

Common Mistakes:

• Using wrong parameter type
• Forgetting @ParameterizedTest annotation
• Misusing assertTrue in parameterized tests

5. You want to test a method that checks if a number is even using @ParameterizedTest with multiple inputs including 0, -2, and 3. Which of the following test method signatures and annotations correctly achieve this?

hard

A. @ParameterizedTest
@ValueSource(ints = {0, -2, 3})
void testIsEven(int number) {
assertEquals(number % 2, 0);
}

B. @ParameterizedTest
@ValueSource(ints = {0, -2, 3})
void testIsEven(int number) {
assertEquals(0, number % 2);
}

C. @ParameterizedTest
@CsvSource({"0, true", "-2, true", "3, false"})
void testIsEven(int number, boolean expected) {
assertEquals(expected, number % 2 == 0);
}

D. @ParameterizedTest
@CsvSource({"0, true", "-2, true", "3, false"})
void testIsEven(String number, boolean expected) {
assertEquals(expected, Integer.parseInt(number) % 2 == 0);
}

Solution

1. Step 1: Understand input and expected output

   We want to test numbers with expected boolean results, so two parameters are needed.

2. Step 2: Check annotation and method signature

   @CsvSource allows multiple parameters; method parameters match types (int, boolean) and assertion compares expected with actual.

3. Step 3: Analyze other options

   Options A and B have incorrect assertEquals argument order or logic; D uses String parameter unnecessarily.

4. Final Answer:

   Option C correctly uses @CsvSource with matching parameters and assertion -> Option C

5. Quick Check:

   Use @CsvSource for multiple inputs and expected results [OK]

Hint: Use @CsvSource for inputs plus expected results [OK]

Common Mistakes:

• Using wrong assertEquals argument order
• Mismatching parameter types
• Using @ValueSource when multiple parameters needed