How to format hour minute from time interval in Swift

func format(second: TimeInterval) -> String? {
    let formatter = DateComponentsFormatter()
    formatter.unitsStyle = .positional
    formatter.allowedUnits = [.hour, .minute]
    formatter.zeroFormattingBehavior = .pad
    return formatter.string(from: second)
}

XCTAssertEqual(format(second: 5400 ), "1:30")
XCTAssertEqual(format(second: 7200), "2:00")
XCTAssertEqual(format(second: 39600 ), "11:00")

func format(minute: Int) -> String {
    let h = minute / 60
    let m = minute % 60
    return "\(h.padZero()):\(m.padZero())"
}

private extension Int {
    func padZero() -> String {
        return String(format: "%02d", self)
    }
}

XCTAssertEqual(format(minute: 90 ), "01:30")
XCTAssertEqual(format(minute: 120), "02:00")
XCTAssertEqual(format(minute: 660 ), "11:00")