Adding the table view for the to-do items

As always, we start with a test. But before we can write the test, we need a new test class. Follow these steps to add a test class for the view controller that shows the to-do items:

1. Select the ToDoTests group in the Project navigator and add a new file from the File menu in Xcode. Select the template from iOS | Source | Unit Test Case Class and then click Next. Insert the name ToDoItemsListViewControllerTests.
2. In the created file, add @testable import ToDo and remove the two template test methods.
3. Add a property for the system under test (sut):

   // ToDoItemsListViewControllerTests.swift
   class ToDoItemsListViewControllerTests: XCTestCase {
    
     var sut: ToDoItemsListViewController!
    
     override func setUpWithError() throws {
       // Put setup code here. This ...
     }
    
     override func tearDownWithError() throws {
       // Put teardown code here. This ...