Snapshot Testing @ CocoaheadsNL

Snapshot
Testing
Lars Lockefeer

struct Person {
let name: String
let age: Int?
}

struct Person {
let name: String
let age: Int?
init?(fromJSON json: [String: AnyObject]) {
guard let name = json["name"] as? String else {
return nil
}
self.name = name
self.age = json["age"] as? Int
}
}

func testValidJsonResultsInCorrectModel() {
let person = Person(fromJSON: [
"name": "Lars Lockefeer",
"age": 42
])
XCTAssertNotNil(person)
XCTAssertEqual(person?.name, "Lars Lockefeer")
XCTAssertEqual(person?.age, 42)
}

func testValidJsonResultsInCorrectModel2() {
"name": "Lars Lockefeer"
])
XCTAssertNotNil(person)
XCTAssertEqual(person?.name, "Lars Lockefeer")
XCTAssertNil(person?.age)
}

func testInvalidJsonResultsInNil() {
"age": 42
])
XCTAssertNil(person)
}

Faster & Better
Implementation

class MyTableViewCell {
@IBOutlet weak var nameLabel: UILabel!
@IBOutlet weak var photoImageView: UIImageView!
@IBOutlet weak var ratingControl: RatingControl!
}

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
/// Dequeue cell etc.
let product = products[indexPath.row]
cell.nameLabel.text = product.name
cell.photoImageView.image = product.photo
cell.ratingControl.rating = product.rating
}

func testProductCellLayout() {
let view = ProductCell()
view.nameLabel.text = "Peanut butter"
view.photoImageView.image = UIImage(named: "placeholder")
view.ratingControl.rating = 5
validateView(view)
}

Testing View Controllers is hard.
-- Everybody, always, everywhere.

class ProductDetailsViewController: UIViewController {
private let titleLabel: UILabel
// ... More properties ...
init(urlSession: NSURLSession, moc: NSManagedObjectContext, cache: DiskCache) {
self.urlSession = urlSession
// ...
}
func viewDidLoad() {
// ...
session.dataTaskWithURL("https://domain.tld/api/products/123") { data, response, error in
// ...
titleLabel = data["title"]
}
}
}

→ Image
→ Title
→ Price
→ Tags

class ProductDetailsViewModel {
typealias Observer = (UIImage, String, [String], Money) -> ()
private var loadObservers: [Observer]
init(urlSession: NSURLSession, moc: NSManagedObjectContext, cache: DiskCache) {
urlSession.dataTaskWithURL("https://domain.tld/api/products/123") { data, response, error in
// ...
for observer in self.loadObservers {
observer(data["image"], data["title"], data["tags"], data["price"])
}
}
}
func subscribe(observer: Observer) {
loadObservers.append(observer)
}
}

init(viewModel: ProductDetailsViewModel) {
self.viewModel = viewModel
// ...
}
func viewDidLoad() {
// ...
viewModel.subscribe { image, title, tags, price in
titleLabel.title = title
// ...
}
}
}

typealias Observer = (UIImage, String, [String], Money) -> ()
protocol ProductDetailsViewModelType {
func subscribe(observer: Observer)
}

init(viewModel: ProductDetailsViewModelType) {
// ...
}
}
extension ProductDetailsViewModel: ProductDetailsViewModelType {}

struct Mock: ProductDetailsViewModelType {
observer(UIImage(named: "placeholder"), "Test Product", ["Tag 1", "Tag 2", "Tag 3"], Money(cents: 999))
}
}
func testProductDetailViewControllerLayout() {
let viewModel = Mock()
let viewController = ProductDetailsViewController(viewModel: viewModel)
validateViewOfViewController(viewController)
}

struct Mock: ProductDetailsViewModelType {
let image: UIImage
let title: String
let tags: [String]
let price: Money
observer(image, title, tags, price)
}
}

func testProductDetailViewControllerLayout() {
let viewModel = Mock(
image: UIImage(named: "placeholder"),
title: "Test Product",
tags: ["Tag 1, Tag 2, Tag 3"]
price: Money(cents: 999)
)
}

func testProductDetailViewControllerEdgeCases() {
let viewModel = Mock(
image: UIImage(named: "placeholder"),
title: "A really long name, that won't fit the view. Let's see what it does.",
tags: ["Tag 1", "Tag 2", "Tag 3", "Tag 4", "Tag 5", ..., "Tag 99", "Tag 100"]
price: Money(cents: 999999999)
)
}

→ FBSnapshotTestCase
→ Kaleidoscope
→ Second Curtain

Thanks for listening!
Questions?
lars.lockefeer@teampicnic.com
@larslockefeer

Snapshot Testing @ CocoaheadsNL

More Related Content

What's hot (20)

Similar to Snapshot Testing @ CocoaheadsNL (20)

Recently uploaded (20)

Snapshot Testing @ CocoaheadsNL