We start the implementation of DetailViewController with the creation of a test case. Select the ToDoTests group in Project Navigator and go to iOS | Source | Unit Test Case Class. Let's name it DetailViewControllerTests, and select the Controller folder as the destination location. Import the @testable import ToDo main module and delete the two template test methods.
Going by the screenshots we've seen in Chapter 2, Planning and Structuring Your Test-Driven iOS App, we know that DetailViewController needs a map view, four labels, and a button. Here, we will only show the TDD process for one label and the button. Add the following code to DetailViewControllerTests:
func test_HasTitleLabel() {
let storyboard = UIStoryboard(name: "Main",
bundle: nil)
let sut = storyboard
.instantiateViewController...