IntroducePolymorphicCreationWithFactoryMethod2.swift

protocol OutputBuilder {
  func addElement(_ id: String)
}

class XMLBuilder: OutputBuilder {
    func addElement(_ id: String) {}
}

class DOMBuilder: OutputBuilder {
    func addElement(_ id: String) {}
}

class RandomTest {}

class XMLBuilderTest: RandomTest {
    private var builder: OutputBuilder
    
    public func testAddRoot() {
        builder = XMLBuilder()
        builder.addElement("order")
        builder.addElement("expiringDate")
    }
}

class DOMBuilderTest: RandomTest {
    private var builder: OutputBuilder
    
    public func testAddRoot() {
        builder = DOMBuilder()
        builder.addElement("order")
        builder.addElement("expiringDate")
    }
}