Add failing test for out of bounds exception

Author: klaaspieter

StackViewControllerTests/StackViewControllerTests.swift

@@ -121,6 +121,21 @@ class StackViewControllerTests: XCTestCase {
         XCTAssertEqual([1, 10], stackViewController.items.map { $0.tag })
         XCTAssertEqual(2, stackViewController.childViewControllers.count)
     }
+
+    func testReplaceItems() {
+        stackViewController.items = [
+            createViewWithTag(1),
+            TestViewController(tag: 10)
+        ]
+
+        stackViewController.items = [
+            createViewWithTag(2),
+            TestViewController(tag: 20)
+        ]
+
+        XCTAssertEqual([2, 20], stackViewController.items.map { $0.tag })
+        XCTAssertEqual(2, stackViewController.childViewControllers.count)
+    }
 }
 
 private extension StackViewItem {