StubKit
A smart stubbing system.
Installation
Using Swift Package Manager
.package(url: "https://github.com/kateinoigakukun/StubKit.git", from: "0.1.0"),
Carthage
Usinggithub "kateinoigakukun/StubKit"
CocoaPods
Usingpod "SwiftStubKit"
Usage
Getting started
You can instantiate any kind of Decodable
with a single line.
import StubKit
// Codable struct
struct User: Codable {
let id: Int
let name: String
let sex: Sex
}
let stubUser = try Stub.make(User.self)
// User(id: 1234, name: "This is Stub String", sex: .female)
Customize property
You can customize properties even if the property is defined as let
.
let maleUser = try Stub.make(User.self) {
$0.set(\.sex, value: .male)
}
// User(id: 1234, name: "This is Stub String", sex: .male)
Stubbable
Using If you want to customize the default stub value, please conform Stubbable
.
extension String: Stubbable {
static func stub() -> String {
return "This is custommized Stub String"
}
}
let stubUser = try Stub.make(User.self)
// User(id: 1234, name: "This is customized Stub String", sex: .female)
Advanced Usage
struct RandomIntStubProvider: StubProvider {
func stub<T>(of type: T.Type) -> T? {
if type is Int.Type {
return Int.random(in: 0..<100) as? T
}
return nil
}
}
let userStub = Stub(type: User.self, provider: [RandomIntStubProvider()])
try userStub.make() // User(id: 97)
try userStub.make() // User(id: 54)
try userStub.make() // User(id: 12)
Need to conform non-final class as Stubbable?
You can make it Stubbable
by defining the UnsafeStubbable
.
public protocol UnsafeStubbable: Stubbable {
associatedtype Target = Self
static func unsafeStub() -> Target
}
extension UnsafeStubbable {
public static func stub() -> Self {
return unsafeStub() as! Self
}
}
extension UIImage: UnsafeStubbable {
public static func unsafeStub() -> UIImage {
return #imageLiteral(resourceName: "dummy")
}
}
How does it work
StubKit mainly uses two techniques.
- Traverse using
Decoder
protocol. - Inject value with non-mutable
KeyPath
. - Existential type using
Self
.
Decoder
protocol
Traverse struct using
Swift has Decodable
protocol and if a type conforms to Decodable
, Swift compiler generates some code to decode internally. So we can decode a JSON to Swift struct without any configuration. StubKit uses this system to construct instance through Decoder
. Decoder
is a protocol which provide a value by key or index like JSONDecoder
. If we pass the Decoder
which just provide a stub value recursively, we can instantiate any kind of Decodable
instance.
KeyPath
Inject value with non-mutable I know it's only natural but, Swift can't mutate let
defined property. But Swift has MemoryLayout<T>.offset
which provide the offset to the property from its own address. So actually in memory we can mutate let
property.
Self
Existential type using A protocol that has associatedtype
or uses Self
type can't be existential type. But using Self
for return type of method is only available in Swift4.2. (I think using Self
for type of getter should be also available.) This technique makes Stubbale
type-safely.