Unit Testing UICollectionView.indexPath(for: UICollectionViewCell)

Question

I am trying to unit test this bit of code in a ViewController

    func categoryTextEditedAt(_ cell: UICollectionViewCell, _ text: String) {
        guard let indexPath = self.collectionView.indexPath(for: cell), text != "" else {return}

        //Rest of the codes to be tested
    }

And in my Unit Test to test the above function is as follows:

    func testCategoryTextEditedAt() {
        sut.viewDidLoad()
        sut.collectionView.reloadData()
        let cell = sut.collectionView.dataSource?.collectionView(sut.collectionView, cellForItemAt: IndexPath(item: 0, section: 0))
        sut.categoryTextEditedAt(cell!, "testString")
    }

but I am keep getting 'nil' for the indexPath inside categoryTextEditedAt(:) function. As I debug, I found that inside testCategoryTextEditedAt() cell has a value but self.collectionView.indexPath(for:cell) keeps returning 'nil' for 'indexPath.'

How can I go about this process?

Answer 1

For those who are curious how to unit test collectionViewDelegateMethod:

    func categoryTextEditedAt(_ cell: UICollectionViewCell, _ text: String) {
        guard let indexPath = self.collectionView.indexPath(for: cell), text != "" else {return}

        //Rest of the codes to be tested
    }

you can do something like

func testCategoryTextEditedAt() {
    class MockCV: UICollectionView {
        override func indexPath(for cell: UICollectionViewCell) -> IndexPath? {
            let anyIndexPathWhichEverYoulike = IndexPath(item:0, section:0)
            return anyIndexPathWhichEverYoulike
        }
    }
    sut.collectionView = MockCV()
    let cell = sut.collectionView.dataSource?.collectionView(sut.collectionView, cellForItemAt: IndexPath(item: 0, section: 0))
    sut.categoryTextEditedAt(cell!, "testString")
}