How to test required init(coder:)? - swift

Question

In my custom class WLNetworkClient I had to implement such method:
required init(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
I do not need to use that, but I would like to test this to make 100% code coverage. Do you know how to achieve this?
I tried following way with no success:
let nc = WLNetworkClient(coder: NSCoder())
XCTAssertNotNil(nc)

Answer 1

Production code:
required init?(coder: NSCoder) {
return nil
}
Test:
func testInitWithCoder() {
let archiverData = NSMutableData()
let archiver = NSKeyedArchiver(forWritingWithMutableData: archiverData)
let someView = SomeView(coder: archiver)
XCTAssertNil(someView)
}
Since the required initializer returns nil and does not use the coder, the above code can be simplified to:
func testInitWithCoder() {
let someView = SomeView(coder: NSCoder())
XCTAssertNil(someView)
}

Answer 2

Here is answer which should help you:
let cd = NSKeyedUnarchiver(forReadingWithData: NSMutableData())
let c = CustomTextField(coder:cd)

Answer 3

Answer from Rudolf Adamkovič ist still working with Swift 4:
required init?(coder aDecoder: NSCoder) {
return nil
}
func testInitWithCoder() {
// 1. Arrange
let archiver = NSKeyedArchiver(forWritingWith: NSMutableData())
// 2. Action
let viewController = ViewController(coder: archiver)
// 3. Assert
XCTAssertNil(viewController)
}

Answer 4

I combined Rudolf's answer with Liz's suggestion and ended with the following solution:
let viewController = SomeTableViewController(
presenter: SomePresenterMock(),
coder: NSKeyedUnarchiver(forReadingWith: Data()))
XCTAssert(viewController?.tableView.numberOfSections == 1)
The key here is to use NSKeyedUnarchiver(forReadingWith: Data()) as mock coder, otherwise the test crashes with NSInvalidArgumentException.

Answer 5

I use improved Rudolf's Adamkovič answer:
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
func test_initWithCoder() {
let object = SomeView()
let data = NSKeyedArchiver.archivedData(withRootObject: object)
let coder = NSKeyedUnarchiver(forReadingWith: data)
let sut = SomeView(coder: coder)
XCTAssertNotNil(sut)
}

Answer 6

It seems that all the previous answers stopped working after Swift 5.
I managed to modify #ChikabuZ answer and make it work like this:
func testInitWithCoder() {
// Given
let object = SomeView()
let data = try! NSKeyedArchiver.archivedData(withRootObject: object, requiringSecureCoding: false)
let coder = try! NSKeyedUnarchiver(forReadingFrom: data)
// When
let sut = SomeView(coder: coder)
// Then
XCTAssertNotNil(sut)
}