Measure execution time in milliseconds

measureInMilliseconds.swift

// implemented according to this answer
// https://stackoverflow.com/a/24755958/6641096

func measureInMilliseconds(_ block: () -> ()) -> UInt64 {
    let start = DispatchTime.now()
    block()
    let end = DispatchTime.now()

    // Difference in nano seconds (UInt64)
    let nanoTime = end.uptimeNanoseconds - start.uptimeNanoseconds
    
    // Technically could overflow for long running tests
    let timeInterval = nanoTime / 1_000_000
    return timeInterval
}