@Spy for partial mocking in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a spy object for partial mocking.

JUnit

List<String> list = Mockito.[1](new ArrayList<>());

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

Amock

Bverify

Cspy

Dwhen

Attempts:

3 left

💡 Hint

Common Mistakes

Using mock() instead of spy() causes full mocking, not partial.

Using verify() or when() here is incorrect as they are for verification and stubbing.

The @Spy annotation or Mockito.spy() method creates a spy object that allows partial mocking of real objects.

2fill in blank

medium

Complete the code to stub a method on a spy object.

JUnit

Mockito.[1](spyList.size()).thenReturn(5);

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

Awhen

BdoReturn

Cverify

Dspy

Attempts:

3 left

💡 Hint

Common Mistakes

Using doReturn() without when() can cause confusion in spies.

Using verify() is for checking calls, not stubbing.

Use when() to stub methods on spy objects for partial mocking.

3fill in blank

hard

Fix the error in stubbing a spy method to avoid calling the real method.

JUnit

Mockito.[1](10).when(spyList).size();

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

Awhen

Bspy

Cverify

DdoReturn

Attempts:

3 left

💡 Hint

Common Mistakes

Using when() on spies calls the real method, which may cause errors.

Using verify() does not stub methods.

Using doReturn() avoids calling the real method on a spy during stubbing, preventing side effects.

4fill in blank

hard

Fill both blanks to stub a spy method without calling the real method.

JUnit

Mockito.[1](10).when(spyList).[2]();

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

AdoReturn

Bwhen

Csize

Dclear

Attempts:

3 left

💡 Hint

Common Mistakes

Using when() instead of doReturn() causes the real method to be called.

Using clear() instead of size() changes the method being stubbed.

Use doReturn(10).when(spyList).size() to stub the size() method on a spy without calling the real method.

5fill in blank

hard

Fill both blanks to verify a method call on a spy with a specific argument.

JUnit

Mockito.[1](spyList).[2]("test");

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

Averify

Badd

Cremove

Dclear

Attempts:

3 left

💡 Hint

Common Mistakes

Using doReturn() or when() instead of verify() for checking calls.

Using remove() or clear() instead of add() changes the method verified.

Use verify(spyList).add("test") to check that the add method was called with argument "test" on the spy.