Argument aggregation in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an argument aggregator class that implements ArgumentsAggregator.

JUnit

public class PersonAggregator implements ArgumentsAggregator {
    @Override
    public Person aggregateArguments(ArgumentsAccessor accessor, ParameterContext context) {
        String name = accessor.getString([1]);
        int age = accessor.getInteger(1);
        return new Person(name, age);
    }
}

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Aname

B1

C2

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of 0 for the first argument index.

Using the argument name instead of index.

The first argument index is 0, so accessor.getString(0) correctly retrieves the first argument.

2fill in blank

medium

Complete the code to use the custom aggregator in a parameterized test.

JUnit

@ParameterizedTest
@CsvSource({"John,25", "Jane,30"})
void testPerson(@AggregateWith(PersonAggregator.class) Person person) {
    assertNotNull([1]);
}

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APerson

Bperson.name

Cperson

Dthis.person

Attempts:

3 left

💡 Hint

Common Mistakes

Using the class name 'Person' instead of the parameter.

Trying to access fields without checking the object.

The parameter 'person' is the aggregated object, so assertNotNull(person) checks it is created.

3fill in blank

hard

Fix the error in the aggregator method to correctly retrieve the age argument as an integer.

JUnit

public Person aggregateArguments(ArgumentsAccessor accessor, ParameterContext context) {
    String name = accessor.getString(0);
    int age = accessor.[1](1);
    return new Person(name, age);
}

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AgetString

BgetInteger

CgetInt

DgetAge

Attempts:

3 left

💡 Hint

Common Mistakes

Using getString to get an integer value.

Using non-existent methods like getInt or getAge.

ArgumentsAccessor provides getInteger(int index) to retrieve integer arguments.

4fill in blank

hard

Fill both blanks to create a parameterized test method that uses the aggregator and asserts the person's age.

JUnit

@ParameterizedTest
@CsvSource({"Alice,28"})
void testPersonAge(@AggregateWith(PersonAggregator.class) Person [1]) {
    assertEquals([2], [1].getAge());
}

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Aperson

Bage

C28

D35

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different parameter name in the assertion.

Using the wrong age value for the assertion.

The parameter name is 'person', and the first test case age is 28, so assertEquals(28, person.getAge()) is correct.

5fill in blank

hard

Fill all three blanks to implement an aggregator that combines first and last names into fullName and returns a Person.

JUnit

public class FullNameAggregator implements ArgumentsAggregator {
    @Override
    public Person aggregateArguments(ArgumentsAccessor accessor, ParameterContext context) {
        String firstName = accessor.getString([1]);
        String lastName = accessor.getString([2]);
        String fullName = firstName + " " + lastName;
        int age = accessor.getInteger([3]);
        return new Person(fullName, age);
    }
}

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A0

B1

C2

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up argument indexes.

Using indexes outside the arguments range.

The first name is at index 0, last name at 1, and age at 2 in the arguments.