     
     func testIndexBasedUpdateMethodByReplacingSameKey() {
         var orderedDictionary: OrderedDictionary<String, Int> = ["A": 1, "B": 2, "C": 3]
-        let previousElement = try! orderedDictionary.update((key: "B", value: 42), at: 1)
+        let previousElement = orderedDictionary.update((key: "B", value: 42), at: 1)
         
         XCTAssertEqual(orderedDictionary.count, 3)
         XCTAssertTrue(previousElement! == ("B", 2))

    
    func testIndexBasedInsertionsWithUniqueKeys() {
        var orderedDictionary: OrderedDictionary<String, Int> = ["A": 1, "B": 2, "C": 3]
        try! orderedDictionary.insert((key: "T", value: 15), at: 0)
        try! orderedDictionary.insert((key: "U", value: 16), at: 2)
        try! orderedDictionary.insert((key: "V", value: 17), at: 5)
        try! orderedDictionary.insert((key: "W", value: 18), at: 2)
        
        let expected: OrderedDictionary<String, Int> = ["T": 15, "A": 1, "W": 18, "U": 16, "B": 2, "C": 3, "V": 17]
        let actual = orderedDictionary

    }
    
    func testIndexBasedUpdateMethodByDuplicatingKey() {
        let orderedDictionary: OrderedDictionary<String, Int> = ["A": 1, "B": 2, "C": 3]
        
        let element = (key: "A", value: 42)
        
        XCTAssertTrue(orderedDictionary.canUpdate(element, at: 0))
        XCTAssertFalse(orderedDictionary.canUpdate(element, at: 1))
        XCTAssertFalse(orderedDictionary.canUpdate(element, at: 2))
    }
    
    func testRetrievingElementAtNonExistentIndex() {
