Why mocking isolates units under test in JUnit - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a mock object using Mockito.

JUnit

UserService userService = Mockito.[1](UserService.class);

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

Averify

Bspy

Cmock

Dwhen

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'spy' instead of 'mock' creates a partial mock, not a full mock.

Using 'verify' or 'when' are for other purposes, not creating mocks.

Mockito.mock() creates a mock object that simulates the behavior of the real class.

2fill in blank

medium

Complete the code to stub a method call on the mock to return a specific value.

JUnit

Mockito.[1](userService.getUserName()).thenReturn("Alice");

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

Averify

Bwhen

Cmock

Dspy

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'verify' instead of 'when' confuses verification with stubbing.

Using 'mock' or 'spy' here is incorrect as they create or wrap objects.

Mockito.when() is used to specify what a mock should return when a method is called.

3fill in blank

hard

Fix the error in the verification statement to check if getUserName() was called once.

JUnit

Mockito.verify(userService, Mockito.[1]()).getUserName();

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

Atimes(1)

BatLeastOnce()

Cnever()

Dtimes(2)

Attempts:

3 left

💡 Hint

Common Mistakes

Using times(2) checks for two calls, which is incorrect here.

Using never() checks that the method was not called, which is wrong.

Using atLeastOnce() allows multiple calls, not exactly one.

Mockito.times(1) verifies that the method was called exactly once.

4fill in blank

hard

Fill both blanks to stub a method and verify it was called with a specific argument.

JUnit

Mockito.[1](userService.getUserById([2])).thenReturn(new User("Bob"));
Mockito.verify(userService).getUserById(5);

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

Awhen

Bverify

C5

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using verify() in the first blank is wrong because it is for checking calls, not stubbing.

Using 10 instead of 5 causes verification to fail.

Use when() to stub the method call with argument 5, then verify it was called with 5.

5fill in blank

hard

Fill all three blanks to create a mock, stub a method, and verify the call.

JUnit

UserRepository repo = Mockito.[1](UserRepository.class);
Mockito.[2](repo.findUserByEmail([3])).thenReturn(new User("Eve"));
Mockito.verify(repo).findUserByEmail("[e-mail]");

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

Amock

Bwhen

C"[e-mail]"

Dspy

Attempts:

3 left

💡 Hint

Common Mistakes

Using spy() instead of mock() creates a partial mock, not a full mock.

Not passing the correct email string causes verification to fail.

First, create a mock with mock(), then stub the method with when(), passing the email string as argument.