Add test cases mentioned in trekhleb#308

Author: cascandaliato

src/algorithms/sets/combination-sum/__test__/combinationSum.test.js

@@ -2,6 +2,16 @@ import combinationSum from '../combinationSum';
 
 describe('combinationSum', () => {
   it('should find all combinations with specific sum', () => {
+    expect(combinationSum([1], 100000)).toHaveLength(1);
+
+    expect(
+      combinationSum([1], 100000)[0]
+        .every(el => el === 1),
+    )
+      .toBe(true);
+
+    expect(combinationSum([0, 2], 6)).toEqual([[2, 2, 2]]);
+
     expect(combinationSum([1], 4)).toEqual([
       [1, 1, 1, 1],
     ]);