CS61B: Lecture 6

Testing

• If we write a function to test the output of a unit of our code to a pre-determined output, that is called a unit test.
• Ex: Sorting function for an array of strings.

public class Sort {
    public static int findSmallest(String[] x, int s) {
        int smallest = s;
        for (int i = s; i < x.length; i+=1) {
            if (x[i].compareTo(x[smallest]) < 0) {
                smallest = i;
            }
        }
        return smallest;
    }

    public static void swap(String[] x, int a, int b) {
        String temp = x[a];
        x[a] = x[b];
        x[b] = temp;
    }

    public static void sort(String[] x) {
        sort(x, 0);
    }

    /*
     * Helper methods could be used to use recursion
     * in a method that does not support recorsion
     */
    private static void sort(String[] x, int s) {
        if (s == x.length) {
            return ;
        }
        int smallest = findSmallest(x, s);
        swap(x, s, smallest);
        sort(x, s+1);
    }
}

String[] test = {"cat", "bob", "luka", "c++ is ..."};
Sort.sort(test);
Arrays.toString(test);

[bob, c++ is ..., cat, luka]

• A unit test for example would look like the following:

%classpath add jar ../../cs61b/library-sp25/*.jar

public class TestSort {
    @Test
    public static void testSort() {
        String[] input = {"cat", "bob", "luka", "c++ is ..."};
        String[] expected = {"bob", "cat", "C++ is ...", "luka"};
        Sort.sort(input);

        assertThat(input).isEqualTo(expected);
    }

    @Test
    public static void testFindSmallest() {
        String[] input = {"cat", "bob", "luka", "c++ is ..."};
        int expected = 1;
        int actual = Sort.findSmallest(input, 0);
        
        assertThat(input).isEqualTo(expected);
    }

    @Test
    public static void testSwap() {
        String[] input = {"cat", "bob", "luka", "c++ is ..."};
        String[] expected = {"bob", "cat", "luka", "c++ is ..."};
        Sort.swap(input, 0, 1);
        
        assertThat(input).isEqualTo(expected);
    }
}