import org.junit.Assert;

import org.junit.Test;

import java.util.*;

public class CombinationsTest {

@Test

public void testCombine() {

Combinations c = new Combinations();

Assert.assertTrue(c.combine(2, 0).isEmpty());

List<List<Integer>> list0 = c.combine(2, 1);

Set<List<Integer>> tmp = new HashSet<>();

tmp.add(Collections.singletonList(1));

tmp.add(Collections.singletonList(2));

Assert.assertTrue(list0.size() == 2);

Assert.assertEquals(new HashSet<>(list0), tmp);

tmp.clear();

List<List<Integer>> list1 = c.combine(4, 2);

tmp.add(Arrays.asList(2, 4));

tmp.add(Arrays.asList(3, 4));

tmp.add(Arrays.asList(2, 3));

tmp.add(Arrays.asList(1, 2));

tmp.add(Arrays.asList(1, 3));

tmp.add(Arrays.asList(1, 4));

Assert.assertTrue(list1.size() == 6);

Assert.assertEquals(new HashSet<>(list1), tmp);

tmp.clear();

List<List<Integer>> list2 = c.combine(4, 3);

tmp.add(Arrays.asList(1, 2, 3));

tmp.add(Arrays.asList(1, 2, 4));

tmp.add(Arrays.asList(1, 3, 4));

tmp.add(Arrays.asList(2, 3, 4));

Assert.assertTrue(list2.size() == 4);

Assert.assertEquals(new HashSet<>(list2), tmp);

}

}