Dummy objects in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a dummy object for the Logger interface.

JUnit

Logger dummyLogger = [1];

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ALogger()

Bnew Logger()

Cdummy(Logger.class)

Dmock(Logger.class)

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to instantiate an interface directly with new.

Using a non-existent method like dummy().

In JUnit with Mockito, mock(Logger.class) creates a dummy object for the Logger interface.

2fill in blank

medium

Complete the code to create a dummy List object using Mockito.

JUnit

List<String> dummyList = [1];

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Amock(List.class)

BList()

Cdummy(List.class)

Dnew ArrayList<>()

Attempts:

3 left

💡 Hint

Common Mistakes

Using new ArrayList() which is a real object, not a dummy.

Trying to call dummy() which does not exist.

Mockito's mock(List.class) creates a dummy List object for testing.

3fill in blank

hard

Fix the error in the dummy object creation for the Service interface.

JUnit

Service dummyService = [1];

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Amock(Service.class)

Bnew Service()

Cdummy(Service.class)

DService()

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to instantiate interface with new.

Using a non-existent dummy() method.

Interfaces cannot be instantiated with new. Use Mockito's mock(Service.class) to create a dummy.

4fill in blank

hard

Fill both blanks to create a dummy object and verify it was used once.

JUnit

Repository dummyRepo = [1];
verify(dummyRepo).[2]();

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Amock(Repository.class)

Bsave

Cdelete

Dnew Repository()

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to instantiate interface with new.

Verifying a method that was not called.

Create a dummy with mock(Repository.class) and verify the save() method was called.

5fill in blank

hard

Fill all three blanks to create a dummy object, stub a method, and assert the stubbed value.

JUnit

Calculator dummyCalc = [1];
when(dummyCalc.[2](5, 3)).thenReturn([3]);
assertEquals(8, dummyCalc.add(5, 3));

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Amock(Calculator.class)

Badd

C8

Dcalculate

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong method names in stubbing.

Not stubbing the method before asserting.

Create a dummy with mock(Calculator.class), stub the add method to return 8, and assert the result.