SelectionSortTest.java

package com.mathieupauly.selectionsort;

import org.junit.Test;

import static org.assertj.core.api.Assertions.assertThat;

public class SelectionSortTest {

    private SelectionSort selectionSort = new SelectionSort();

    @Test
    public void empty() {
        final int[] array = {};
        selectionSort.sort(array);
        assertThat(array).isEqualTo(new int[]{});
    }

    @Test
    public void two_element_sorted() {
        final int[] array = {0, 1};
        selectionSort.sort(array);
        assertThat(array).isEqualTo(new int[]{0, 1});
    }

    @Test
    public void test() {
        final int[] array = {1, 0};
        selectionSort.sort(array);
        assertThat(array).isEqualTo(new int[]{0, 1});
    }

}

class SelectionSort {
    public void sort(int[] array) {
        int minIndex;
        for (int i = 0; i < array.length - 1; i++) {
            minIndex = i;
            for (int j = i + 1; j < array.length; j++) {
                if (array[j] < array[minIndex]) {
                    minIndex = j;
                }
            }
            if (minIndex != i) {
                int tmp = array[i];
                array[i] = array[minIndex];
                array[minIndex] = tmp;
            }
        }
    }
}