ContactsTests.kt

data class Contact(val name:String, val phoneNum:String)

interface ContactsListsApi{
  fetchContacts(): Single<List<Contact>>
}
interface ContactsListsContract{
  interface View{
    fun showProgress()
    fun hideProgress()
    fun setData(contacts: List<Contact>)
  }
  interface Presenter{
    fun fetchContacts()
  }
}

class ContactsListPresenter(val view: ContactsListsContract.View, val api:ContactsListsApi): ContactsListsContract.Presenter {
  override fun fetchContacts(){
    view.showProgress()
    fetchContacts()
      .subscribe(
        {
          view.hideProgress()
          view.setData(it)
        },
        {
          view.hideProgress()
          view.showError(it.message ?: "Unknown error")
        }
  }
}