Swift extensions and Unit Tests

Question

I have a issue with some UT I'm trying to write in swift

I have a protocol with an extension that "does stuff" :

protocol MyProtocol: class
{
    var myVar: SomeClass { get }

    func doStuff(identifier: String) -> Bool
}

extension MyProtocol
{
    func doStuff(identifier: String) -> Bool {
        return true
    }
}

And then a class that implements my protocol

final class MyClass: MyProtocol {

}

And this class has an extension that implements an other protocol which have a method I'm supposed to test

public protocol MyOtherProtocol: class {
    func methodToTest() -> Bool
}

extension MyClass: MyOtherProtocol {
    public func methodToTest() {
        if doStuff() {
            return doSomething()
        }

    }
}

Is there a way with this setup to mock doStuff method ?

Answer 1

It is a good practice to address Protocols instead of Classes. So instead of extending you class you can extend protocol

extension MyOtherProtocol where Self: MyProtocol {
    public func methodToTest() {
        if doStuff() {
            return doSomething()
        }

    }
}

So your extension will aware, that doStuff exists, but not aware about its implementation. And then make you class conforms to both.

extension MyClass: MyOtherProtocol {}

So in mock you can implement

class MyMockClass: MyProtocol, MyOtherProtocol {
    func doStuff() -> Bool {
        return true
    }
}