when().thenThrow() for exceptions in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to mock a method to throw an exception using when().thenThrow().

JUnit

when(mockedList.[1](0)).thenThrow(new IndexOutOfBoundsException());

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

Aremove

Bget

Cadd

Dclear

Attempts:

3 left

💡 Hint

Common Mistakes

Using methods like add or clear which do not take an index parameter.

Trying to mock a method that does not throw IndexOutOfBoundsException.

The get method is commonly mocked to throw exceptions like IndexOutOfBoundsException when accessing invalid indexes.

2fill in blank

medium

Complete the code to mock a service method to throw a custom exception.

JUnit

when(userService.[1](anyString())).thenThrow(new UserNotFoundException());

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

AfindUserById

BdeleteUser

CupdateUser

DcreateUser

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing methods that create or update users which usually do not throw not found exceptions.

Using methods that do not accept a string parameter.

The method findUserById is typically used to retrieve a user and can throw UserNotFoundException if the user does not exist.

3fill in blank

hard

Fix the error in the code to correctly mock throwing an exception with when().thenThrow().

JUnit

when(mockedMap.get([1])).thenThrow(new NullPointerException());

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

A"key"

Bkey

Cnull

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Passing an unquoted string which causes compilation errors.

Passing null which is valid but not the intended key here.

The get method expects a key object. To pass a string key, it must be in quotes.

4fill in blank

hard

Fill both blanks to mock a method that throws an IllegalArgumentException when called with a negative number.

JUnit

when(calculator.[1]([2])).thenThrow(new IllegalArgumentException());

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

Adivide

B-5

Cadd

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using the add method which usually does not throw exceptions for negative inputs.

Passing positive numbers instead of negative.

The divide method can throw an exception when dividing by a negative number like -5.

5fill in blank

hard

Fill all three blanks to mock a repository method that throws SQLException when saving a null entity.

JUnit

when(repository.[1]([2])).thenThrow(new [3]());

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

Asave

Bnull

CSQLException

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using delete instead of save which may not throw SQLException here.

Passing a non-null argument instead of null.

The save method throws SQLException when called with a null entity.