TDD

Question 1

TDD steps

Answer 1

It has four steps:

1. Write a failing test
2. Make the test pass
3. Refactor
4. Repeat

Red: Write a failing test, before writing any app code.

Green: Write the bare minimum code to make the test pass.

Refactor: Clean up both your app and test code.

Repeat: Do this cycle again until all features are implemented.

Question 2

Test conventions

Answer 2

• XCTest: Requires all test methods begin with test to be run.
• test: Followed by the name of the method being tested. Here, this is init. There’s then an underscore to separate it from the next part.

Optionally, if special set up is required, this comes next. This test doesn’t include this. If provided, this likewise is followed by an underscore to separate it from the last part.

Lastly, this is followed by the expected outcome or result. Here this is createsCashRegister.

Question 3

A few things you might look to refactor in refactor state in TDD

Answer 3

Duplicate logic

Comments

Code smells

Question 4

Three parts of test

Answer 4

Given a certain condition…

When a certain action happens…

Then an expected result occurs.

Question 5

In which order are test methods executed?

Answer 5

The order in which test classes and test methods are run is not explicitly defined and cannot be relied upon.

Question 6

Lifecycle of XCTestCase

Answer 6

XCTestCase subclass lifecycles are managed outside the test execution, and any class-level state is persisted between test methods.

Question 7

When setUp() and tearDown() are executed?

Answer 7

After and before each test

Question 8

Organisation of test target folder

Answer 8

Question 9

@testable attribute

Answer 9

Xcode provides a way to expose data types for testing without making them available for general use

This makes symbols that are open, public, and internal available to the test case.

Question 10

Not compiling counts as a failure?

Answer 10

yes

Question 11

Use tests to guide … what?

Answer 11

Use tests to guide refactoring code for readability and performance.

Question 12

Functonal view controller testing is done by?

Answer 12

Functional testing is done by using separate methods for interacting with the UI (callbacks, delegate methods, etc.) from logic methods (updating state).

Question 13

Using the host app

Answer 13

you have access to the UIApplication object and the whole View hierarchy in the tests.

One alternate way of retrieving and testing a view controller can be done as follows: First, get a reference to the storyboard:

Question 14

Turn on Randomized order

Answer 14

Question 15

Code coverage

Answer 15

Coverage doesn’t mean the code works, but lack of coverage means that it’s not tested. For views and view controllers, it’s not expected to get to 100% coverage because TDD does not include UI testing. When you combine unit tests with UI automation tests, then you should expect to be able to cover most if not all of these files.

Question 16

Debugging tests

Answer 16

Make sure:

You have the right assumptions in the given statements.

Your then statements accurately reflect the desired behavior.

Question 17

Using test breakpoints

Answer 17

Question 18

XCTest expectations have two parts:

Answer 18

the expectation and a waiter. An expectation is an object that you can later fulfill. The wait method of XCTestCase tells the test execution to wait until the expectation is fulfilled or a specified amount of time passes.

Question 19

Testing for true asynchronicity

Answer 19

Create custom class that observe if text/color/font changes when “when” part happens in test and fulfill expectation within this class

Question 20

What expectation can expect?

Answer 20

NotificationCenter
exp.fulfill()

pro

Question 21

expectedFulfillmentCount

Answer 21

You can use
expectedFulfillmentCount to set how many times you have to fulfill exp

Question 22

Expecting something not to happen

Answer 22

exp.isInverted = true
you can invert expectation

Question 23

What you can add to Notification?

Answer 23

You can add data through userInfo[:]

Question 24

Expectation can be set. How?

Answer 24

Question 25

You can check an array of expectations with order

Answer 25

enforceOrder parameter

Question 26

Describe exceptions and what they can do

Answer 26

fulfill
Notifications
Arrays
invert
set fulfilling many times

Use XCTestExpectation and its subclasses to make tests wait for asynchronous process completion.

Test expectations help test properties of the asynchronicity, like order and number of occurrences, but XCTAssert functions should still be used to test state.

Question 27

Remove item from array

Answer 27

Question 28

XCTKVOExpectation and XCTNSPredicateExpectation

Answer 28

Question 29

Type of test doubles

Answer 29

Stub: Stubs stand in for the original object and provide canned responses. These are often used to implement one method of a protocol and have empty or nil returning implementations for the others.

Fake: Fakes often have logic, but instead of providing real or production data, they provide test data. For example, a fake network manager might read/write from local JSON files instead of connecting over a network.

Mock: Mocks are used to verify behavior, that is they should have an expectation that a certain method of the mock gets called or that its state was set to an expected value. Mocks are generally expected to provide test values or behaviors.

Partial mock: While a regular mock is a complete substitution for a production object, a partial mock uses the production code and only overrides part of it to test the expectations. Partial mocks are usually a subclass or provide a proxy to the production object.

Question 30

Mock static

Answer 30

Question 31

How to test view?

Answer 31

Subclass view that you want to test and override logic

Then inject this view to your SUT (view controller)

Make some changes on view controller

Asset what is needed

Question 32

Test doubles let you

Answer 32

test code in isolation from other systems, especially those that are part of system SDKs, rely on networking or timers.

Question 33

Mocks let you

Answer 33

swap in a test implementation of a class, and partial mocks let you just substitute part of a class.

Question 34

Fakes let you

Answer 34

supply data for testing or use in Simulator.

Question 35

Testing for time dependencies

Answer 35

During tests, use a very short timer (e.g., one millisecond instead of one second).

Swap the timer for a mock that executes the callback immediately.

Use the callback directly, and save the timing for an app or user-acceptance testing.

Question 36

How to use mockes?

Answer 36

Inject mock to your SUT and test what you want

You need create abstraction layer for your dependency (mock).
Use protocol

Test how SUT is reacting on your mock

Question 37

When to register cells for table view?

Answer 37

on did set

Question 38

How to dequeue different cells in table view?

Answer 38

You can use different method for dequeueing for each cell

Question 39

How to configure cell with viewModel?

Answer 39