Quicksort Test Example

QuicksortTest.java

import static org.fest.assertions.Assertions.*;
import java.util.Arrays;

import org.junit.Test;

public class QuicksortTest {

    Quicksort<String> textSorter = Quicksort.createTextSorter();
    Quicksort<Integer> intSorter = Quicksort.createIntSorter();

    @Test
    public void sortIntArray() {
        Integer[] values = new Integer[] { 5, 6, 3 };
        intSorter.sort(values);
        assertArrayIsSorted(values);
    }

    @Test
    public void sortIntArrayFast() {
        Integer[] values = new Integer[] { 5, 4, 6, 2, 1 };
        intSorter.slowIntegerSort = false;
        intSorter.sort(values);
        assertArrayIsSorted(values);
    }

    @Test
    public void sortTextArray() {
        String[] values = new String[] { "xy", "aa", "bb" };
        textSorter.sort(values);
        assertArrayIsSorted(values);
    }

    static <T extends Comparable<T>> void assertArrayIsSorted(T[] array) {
        assertThat(array)
            .describedAs("A null instance of array could not be verified as sorted.")
            .isNotNull();
        assertThat(array.length)
            .describedAs("A array with one element could not be tested as sorted.")
            .isGreaterThan(1);
        for (int i = 1; i < array.length; i++) {
            T before = array[i - 1];
            T actual = array[i];
            boolean valueBeforeIsSmallerOrEqualsThanActual = before.compareTo(actual) <= 0;
            assertThat(valueBeforeIsSmallerOrEqualsThanActual)
                .describedAs( Arrays.toString(array) + " array is not sorted.")
                .isTrue();
        }
    }
    
}