CSE 331: Section 2 — Testing (Solutions)

Task 1 - Spec Based Testing

Use the testing heuristics from lecture to write a test suite for the following method:

/**
 * Returns the sum of the array
 * @param arr an array of integers
 * @requires arr is not null
 * @returns the sum of the elements
 * in arr or 0 if arr is empty
 */
 public static int arraySum(int[] arr) {...}

@Test
public void testArraySum() {
    // empty array
    int[] arr1 = new int[0];
    assertEquals(0, arraySum(arr1)); 
    // single element array
    int[] arr2 = {5};
    assertEquals(5, arraySum(arr2)); 
    // multi-element array
    int[] arr3 = {0, 3, 3, -1, 0};
    assertEquals(5, arraySum(arr3));
}

Task 2 - Code Coverage

Write JUnit tests for code coverage for the method spec and impl below.

/**
 * Removes x from the prefix a[0..n]
 * @param a the non-null array to remove from
 * @param n the length of the prefix
 * @param x the value to remove
 * @requires 0 <= n <= a.length
 * @modifies a
 * @effects if x does not occur in a[0..n], leaves a unchanged;  otherwise, if x
 *     occurs k > 0 times in a[0..n], then remove all k occurrences of x,
 *     leaving remaining elements in the same relative order as before;
 *     the new value of elements in a[n-k..n] is unspecified.
 * @return n - k
 */
public static int removeValue(int[] a, int n, int x) {
    int w = 0;
    for (int r = 0; r < n; r++) {
        if (a[r] != x) {
            a[w] = a[r];
            w++;
        }
    }
    return w;
}

We have given you a template for the first test. Feel free to use a similar format for additional tests as well. Include a comment in the space provided above each assertion stating which testing heuristic(s) is being covered. Make sure your tests cover all statements, branches, and 0/1/2+ loops.

@Test public void testRemoveValue() {

  int[] arr = {__________________________________________________________________};

  // _____________________________________________________________________________

  assertEquals(__________________________________________________________________);

  assertArrayEquals(_____________________________________________________________);

















}

@Test
public void testRemoveValue() {
    int[] arr = {1, 2, 3};

    // 0 loop iterations
    assertEquals(0, removeValue(arr, 0, 1));
    assertArrayEquals(arr, new int[] {1,2,3});

    // 1 loop iterations & implicit else branch
    assertEquals(0, removeValue(arr, 1, 1));
    assertArrayEquals(arr, new int[] {1,2,3});

    // 2+ loop iterations & if branch
    assertEquals(1, removeValue(arr, 2, 1));
    assertArrayEquals(arr, new int[] {2,2,3});
}

Task 3 - Interactive Programming: Designing for Testability

/**
 * Reads whitespace-separated integers from standard input and prints
 * either their sum (default) or their average.
 *
 * Usage:
 *   java Sum [options]
 *
 * Options:
 *   -a      print the average instead of the sum
 *
 * Input is read from standard input until end of file.
 */
public static void main(String[] args) {
    boolean average = false;
    if (args.length > 0 && args[0].equals("-a")) {
        average = true;
    }

    Scanner scan = new Scanner(System.in);
    int sum = 0;
    int count = 0;

    while (scan.hasNextInt()) {
        sum += scan.nextInt();
        count++;
    }

    if (average) {
        System.out.println((double) sum / count);
    } else {
        System.out.println(sum);
    }
}

Part A - Decomposition

Identify at least three distinct jobs that main is performing.

Part B - Refactoring

Rewrite the main method by "wishful thinking". Which 2 or 3 helper methods might you create?

public static void main(String[] args) {









}

parseArguments(...)
readNumbers(...)
computeSum(...)
computeAverage(...)
printResult(...)

Part C - Testing

Of the helper methods you listed above, which one would be most valuable to extract if your goal is to make the program easier to unit test? Briefly explain.