Tests for collectionview supplementary views

Author: Alex Little

Tests/CombineDataSourcesTests/CollectionView/CollectionViewItemsControllerTests.swift

@@ -42,13 +42,20 @@ final class CollectionViewItemsControllerTests: XCTestCase {
     // Configure the controller
     let collectionView = UICollectionView(frame: .zero, collectionViewLayout: UICollectionViewFlowLayout())
     collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "Cell")
+    collectionView.register(UICollectionReusableView.self, forSupplementaryViewOfKind: "supplementary-kind", withReuseIdentifier: "supplementaryview")
+
+    ctr.configureSupplementaryView = { _, collection, kind, index, section -> UICollectionReusableView in
+        return collection.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: "supplementaryview", for: index)
+    }
 
     ctr.collectionView = collectionView
     ctr.updateCollection(dataSet2)
 
     XCTAssertNil(lastModel)
     let cell = ctr.collectionView(collectionView, cellForItemAt: IndexPath(row: 0, section: 0))
+    let supplementaryView = ctr.collectionView(collectionView, viewForSupplementaryElementOfKind: "supplementary-kind", at: IndexPath(row: 0, section: 0))
     XCTAssertNotNil(cell)
+    XCTAssertNotNil(supplementaryView)
     XCTAssertEqual("test model", lastModel?.text)
   }
 }