         var chain: TimePeriodChain = TimePeriodChain()
         //Create test TimePeriods to construct same as control
         //Add test periods
-        collectionSame.addTimePeriod(firstPeriod)
-        collectionSame.addTimePeriod(secondPeriod)
-        collectionSame.addTimePeriod(thirdPeriod)
-        collectionSame.addTimePeriod(fourthPeriod)
-        chain.addTimePeriod(firstPeriod)
-        chain.addTimePeriod(secondPeriod)
-        chain.addTimePeriod(thirdPeriod)
-        chain.addTimePeriod(fourthPeriod)
+        collectionSame.add(firstPeriod)
+        collectionSame.add(secondPeriod)
+        collectionSame.add(thirdPeriod)
+        collectionSame.add(fourthPeriod)
+        chain.add(firstPeriod)
+        chain.add(secondPeriod)
+        chain.add(thirdPeriod)
+        chain.add(fourthPeriod)
         //Test same as control
         XCTAssertTrue(self.controlCollection.hasSameCharacteristicsAs(collectionSame))
         //Test differnt chain

    }
    
    // MARK: - Group Info
    func testDurationInYears() {
        XCTAssertEqual(3, self.controlCollection.durationInYears)
    }
    
    func testDurationInWeeks() {
        XCTAssertEqual(156, self.controlCollection.durationInWeeks)
    }

    
    var formatter = DateFormatter()
    var controlCollection = TimePeriodCollection()
    var firstPeriod = TimePeriod()
    var secondPeriod = TimePeriod()
    var thirdPeriod = TimePeriod()
    var fourthPeriod = TimePeriod()
    
    override func setUp() {
        //Initialize control TimePeriodChain
        self.controlCollection = TimePeriodCollection()
        //Initialize formatter
        self.formatter.dateFormat = "yyyy MM dd HH:mm:ss.SSS"
        //Create test TimePeriods that are 1 year long
        firstPeriod = TimePeriod(beginning: self.formatter.date(from: "2014 11 05 18:15:12.000")!, end: self.formatter.date(from: "2015 11 05 18:15:12.000")!)
        secondPeriod = TimePeriod(beginning: self.formatter.date(from: "2015 11 05 18:15:12.000")!, end: self.formatter.date(from: "2016 11 05 18:15:12.000")!)
        thirdPeriod = TimePeriod(beginning: self.formatter.date(from: "2016 11 05 18:15:12.000")!, end: self.formatter.date(from: "2017 11 05 18:15:12.000")!)
        fourthPeriod = TimePeriod(beginning: self.formatter.date(from: "2015 4 05 18:15:12.000")!, end: self.formatter.date(from: "2017 4 05 18:15:12.000")!)
        //Add test periods
        self.controlCollection.add(firstPeriod)
        self.controlCollection.add(secondPeriod)
        self.controlCollection.add(thirdPeriod)
        self.controlCollection.add(fourthPeriod)
    }
    
    override func tearDown() {
