Testing

Complete the following exercises:

1. Consider two functions that compute the following:
   • The arithmetic mean of an array of doubles
   • The median of an array of doubles

   Write unit tests for these functions.

   mean

   • [] -> None (or some exception)
   • [0] -> 0
   • [0, 2] -> 1
   • [-1, 1] -> 0
   • [0, 1, 2, 3, 4] -> 5

   median

   • [] -> None (or some exception)
   • [0] -> 0
   • [0, 2] -> 1
   • [-1, 1] -> 0
   • [0, 1, 2, 3, 4] -> 2

2. Compare your (black box) test cases to those developed by others. Did you miss any important test cases?

3. Write C or Java code for the aforementioned functions. You may not use any library functions in your implementation.

   /**
    * Calculate and print the median of a set of values.
    */
   public class Median {
     public static void main(String[] args) {
       // convert the arguments to double
       final double[] values = new double[args.length];
       for (int i = 0; i < values.length; i++) {
         final String arg = args[i];
   
         final double value = Double.parseDouble(arg);
         values[i] = value;
       }
   
       final double median = median(values);
       System.out.printf("The median is %.3f%n", median);
     }
   
     /**
      * Compute the arithmetic mean of an array of <code>double</code>s.
      */
     public static double mean(final double[] values) {
       // compute the mean of the entire array
       return mean(values, 0, values.length);
     }
   
     /**
      * Computes the arithmetic mean of a slice of an array.
      *
      * @param values array over which to compute the mean
      * @param start lower index of the array slice (inclusive)
      * @param end upper index of the array slice (exclusive)
      */
     private static double mean(final double[] values, int start, int end) {
       double sum = 0.0;
       for (int i = start; i < end; i++) {
         sum += values[i]; // sum the elements of the array
       }
   
       final double mean = sum / (end - start);
       return mean;
     }
   
     /**
      * Compute the median of an array of <code>double</code>s.
      */
     public static double median(final double[] values) {
       if (values.length == 0) {
         final String message = "Median not defined for an empty array";
         throw new IllegalArgumentException(message);
       }
   
       sort(values); // sort the values
   
       final int midpoint = values.length >> 1; // index of array's midpoint
   
       final double median;
       if ((values.length & 0x01) == 0x01) { // odd number of elements
         median = values[midpoint];
       } else { // even number of elements
         median = mean(values, midpoint - 1, midpoint + 1);
       }
   
       return median;
     }
   
     /**
      * Sort the specified values in ascending order using the insertion sort
      * algorithm.
      */
     private static void sort(double[] values) {
       for (int i = 0; i < values.length; i++) {
         for (int j = i; 0 < j; j--) {
           if (values[j] < values[j - 1]) { // out of order => swap values
             final double tmp = values[j];
             values[j] = values[j - 1];
             values[j - 1] = tmp;
           }
         }
       }
     }
   }
   

4. Draw the control flow graph (CFG) of each function.

   main

   

   mean

   

   median

   

   sort

   

5. Compute the cyclomatic complexity of each function.

   Function	Cyclomatic Number
   main	2
   mean	2
   median	3
   sort	4

6. Exchange your implementations of the aforementioned functions with someone else. Draw the CFG and calculate the cyclomatic complexity of each function. Verify that your CFG and cyclomatic number matches the original author’s.

7. While looking at your code, write unit tests for each function. Organize your test cases as follows:
   • the minimum set required to exercise all statements
   • the minimum set required to exercise all branches
   • the minimum set required to exercise all paths