Fake objects in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a fake object for testing.

JUnit

FakeDatabase fakeDb = mock(FakeDatabase.class);
fakeDb.[1]("testUser");

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

AaddUser

BupdateUser

Cconnect

DdeleteUser

Attempts:

3 left

💡 Hint

Common Mistakes

Using connect instead of addUser will not add a user.

Using deleteUser or updateUser will not add a new user.

The method addUser is used to add a user to the fake database for testing purposes.

2fill in blank

medium

Complete the code to verify the fake object's method was called.

JUnit

verify(fakeDb).[1]("testUser");

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AupdateUser

Bconnect

CaddUser

DdeleteUser

Attempts:

3 left

💡 Hint

Common Mistakes

Verifying connect does not check user addition.

Verifying deleteUser or updateUser is unrelated to adding a user.

We verify that addUser was called on the fake database with the argument "testUser".

3fill in blank

hard

Fix the error in the fake object setup to return a value.

JUnit

when(fakeDb.[1]("testUser")).thenReturn(true);

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Aconnect

BuserExists

CaddUser

DdeleteUser

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to stub addUser which might be void causes errors.

connect and deleteUser do not return boolean values.

The method userExists returns a boolean, so it can be stubbed to return true.

4fill in blank

hard

Fill both blanks to create a fake object and stub a method.

JUnit

FakeDatabase fakeDb = mock([1].class);
when(fakeDb.[2]("admin")).thenReturn(true);

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AFakeDatabase

BRealDatabase

CuserExists

DaddUser

Attempts:

3 left

💡 Hint

Common Mistakes

Using RealDatabase instead of FakeDatabase defeats the purpose of a fake.

Stubbing addUser instead of userExists will not return a boolean.

We create a FakeDatabase object and stub the userExists method to return true for "admin".

5fill in blank

hard

Fill all three blanks to verify method calls and stub behavior on a fake object.

JUnit

FakeDatabase fakeDb = mock([1].class);
when(fakeDb.[2]("guest")).thenReturn(false);
verify(fakeDb).[3]("guest");

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

AFakeDatabase

BRealDatabase

CuserExists

DaddUser

Attempts:

3 left

💡 Hint

Common Mistakes

Using RealDatabase instead of FakeDatabase.

Verifying addUser instead of userExists causes test failures.

Stubbing addUser which does not return a value.

We create a FakeDatabase, stub userExists to return false for "guest", and verify userExists was called with "guest".