unit test custom UITableViewCell? - ios

Question

Is it possible to init and load only custom cell and test outlets?
My ViewController has TableView with separated dataSource ( which is subclass of custom data source ). So it's kinda tricky to create cell using all of those.
Custom cell has only a couple of labels and config method for updating them from object, so if loaded, testing would be easy.

Answer 1

It is possible to write a unit test for custom UITableViewCell that will test its outlets and any other functionality included in it. The following sample demonstrates this:
class TestItemTableViewCell: XCTestCase {
var tableView: UITableView!
private var dataSource: TableViewDataSource!
private var delegate: TableViewDelegate!
override func setUp() {
tableView = UITableView(frame: CGRect(x: 0, y: 0, width: 200, height: 400), style: .plain)
let itemXib = UINib.init(nibName: "ItemTableViewCell",
bundle: nil)
tableView.register(itemXib,
forCellReuseIdentifier: "itemCell")
dataSource = TableViewDataSource()
delegate = TableViewDelegate()
tableView.delegate = delegate
tableView.dataSource = dataSource
}
func testAwakeFromNib() {
let indexPath = IndexPath(row: 0, section: 0)
let itemCell = createCell(indexPath: indexPath)
// Write assertions for things you expect to happen in
// awakeFromNib() method.
}
}
extension TestItemTableViewCell {
func createCell(indexPath: IndexPath) -> ItemTableViewCell {
let cell = dataSource.tableView(tableView, cellForRowAt: indexPath) as! ItemTableViewCell
XCTAssertNotNil(cell)
let view = cell.contentView
XCTAssertNotNil(view)
return cell
}
}
private class TableViewDataSource: NSObject, UITableViewDataSource {
var items = [Item]()
override init() {
super.init()
// Initialize model, i.e. create&add object in items.
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return items.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "itemCell",
for: indexPath)
return cell
}
}
private class TableViewDelegate: NSObject, UITableViewDelegate {
}
This approach mimics the way UITableViewCells are created/reused at runtime. The same methods get called, e.g. awakeFromNib, IBOutlets initialized, etc. I am sure you can even test the sizing of the cell (e.g. height) even though I haven't tried that yet. Note that having a view model where the "visualization" logic of your model object is contained is a good & modular approach and makes it easier to unit test parts of the code (as described in another answer above). However, with a unit test for a view model object, you cannot test the entire lifecycle of a UITableViewCell.

Answer 2

Performing unit tests against that is not really worth the hassle. However, there is an easier approach to this problem.
You can create a view model to support your cell, and then test that the view model is providing the correct values for each item.
A simple example of a view model that populates two labels and an image is here:
class MyCellModel {
var stringOne: String? {
return "Compute string 1"
}
var stringTwo: String? {
return "Compute string 2"
}
var image: UIImage? {
return UIImage(named: "myimage")
}
}
Using this model, you would place the logic for generating those values in the relevant computed properties. Then for testing purposes, you can initialize this model with the values you want to test against.