Stub objects in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a stub that returns a fixed value.

JUnit

StubClass stub = new StubClass() {
    @Override
    public int getValue() {
        return [1];
    }
};

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

A"value"

Btrue

Cnull

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Returning a string instead of an int.

Returning null for a primitive int return type.

The stub method getValue() should return an integer. Returning 10 is correct.

2fill in blank

medium

Complete the code to stub a method that returns a fixed string.

JUnit

StubClass stub = new StubClass() {
    @Override
    public String getName() {
        return [1];
    }
};

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

A100

Bnull

C"TestUser"

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Returning an integer instead of a String.

Returning false instead of a String.

The stub method getName() returns a String. Returning "TestUser" is correct.

3fill in blank

hard

Fix the error in the stub method to return the correct boolean value.

JUnit

StubClass stub = new StubClass() {
    @Override
    public boolean isAvailable() {
        return [1];
    }
};

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

Atrue

Bnull

C1

D"true"

Attempts:

3 left

💡 Hint

Common Mistakes

Returning "true" as a string instead of boolean true.

Returning 1 instead of a boolean.

The method isAvailable() returns a boolean. The correct return is the boolean literal true, not a string or number.

4fill in blank

hard

Fill both blanks to stub a method that returns a list with one fixed element.

JUnit

StubClass stub = new StubClass() {
    @Override
    public List<String> getItems() {
        return [1];
    }
};

List<String> expected = new ArrayList<>();
expected.[2]("item1");

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

Anew ArrayList<>()

Badd

Cremove

Dclear

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove or clear instead of add.

Returning null instead of a new list.

The stub returns a new empty list (new ArrayList<>()), then we add "item1" to the expected list using add.

5fill in blank

hard

Fill all three blanks to stub a method that returns a map with one key-value pair.

JUnit

StubClass stub = new StubClass() {
    @Override
    public Map<String, Integer> getScores() {
        Map<String, Integer> map = [1];
        map.[2]([3], 100);
        return map;
    }
};

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

Anew HashMap<>()

Bput

C"player1"

Dclear

Attempts:

3 left

💡 Hint

Common Mistakes

Using clear instead of put.

Using an unquoted key for the map.

The stub creates a new map with new HashMap<>(), adds a key-value pair using put with key "player1" and value 100, then returns the map.