Mocking with MockK in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is MockK used for in Kotlin testing?

MockK is a library used to create mock objects in Kotlin tests. It helps simulate and control the behavior of dependencies to test code in isolation.

beginner

How do you create a simple mock object with MockK?

Use the function mockk<ClassName>() to create a mock instance of a class. For example, val mock = mockk<MyClass>().

beginner

What does the every { ... } returns ... syntax do in MockK?

It defines the behavior of a mocked function. Inside every { ... } you specify the function call, and returns sets what value it should return when called.

intermediate

How do you verify that a mocked function was called in MockK?

Use the verify { ... } block with the function call inside. This checks if the function was called during the test.

intermediate

What is the difference between mockk() and spyk() in MockK?

mockk() creates a pure mock with no real behavior, while spyk() creates a spy that wraps a real object and allows you to mock or verify some behavior while keeping the original behavior for others.

Which MockK function creates a mock object?

A every()

B spyk()

C mockk()

D verify()

mockk() creates a mock object. spyk() creates a spy, every() sets behavior, and verify() checks calls.

How do you specify what a mocked function should return?

A using <code>spyk()</code>

B using <code>verify { ... }</code>

C using <code>mockk()</code>

D using <code>returns</code> inside <code>every { ... }</code>

You use every { functionCall } returns value to define return values for mocked functions.

What does verify { mock.someFunction() } check?

A That <code>someFunction()</code> was called on <code>mock</code>

B That <code>someFunction()</code> returns a value

C That <code>mock</code> is a spy

D That <code>mock</code> is a real object

verify { ... } checks if the specified function was called on the mock.

Which MockK function lets you keep original behavior but mock some parts?

A mockk()

B spyk()

C every()

D verify()

spyk() creates a spy that wraps a real object, allowing partial mocking.

What is the main purpose of mocking in tests?

A To isolate the code being tested by simulating dependencies

B To make the code run faster

C To write less code

D To create user interfaces

Mocking helps isolate the code under test by simulating dependencies, so tests focus on the code itself.

Explain how to create a mock and define its behavior using MockK.

Think about how you tell a mock what to do when a function is called.

Describe the difference between a mock and a spy in MockK and when you might use each.

Consider if you want to keep original behavior or replace it completely.