merge: Add test case to shellSort algorithm (#975)

Sorts/test/ShellSort.test.js

@@ -0,0 +1,25 @@
+import { shellSort } from '../ShellSort'
+
+test('The ShellSort of the array [5, 4, 3, 2, 1] is [1, 2, 3, 4, 5]', () => {
+  const arr = [5, 4, 3, 2, 1]
+  const res = shellSort(arr)
+  expect(res).toEqual([1, 2, 3, 4, 5])
+})
+
+test('The ShellSort of the array [] is []', () => {
+  const arr = []
+  const res = shellSort(arr)
+  expect(res).toEqual([])
+})
+
+test('The ShellSort of the array [15, 24, 31, 42, 11] is [11, 15, 24, 31, 42]', () => {
+  const arr = [15, 24, 31, 42, 11]
+  const res = shellSort(arr)
+  expect(res).toEqual([11, 15, 24, 31, 42])
+})
+
+test('The ShellSort of the array [121, 190, 169] is [121, 169, 190]', () => {
+  const arr = [121, 190, 169]
+  const res = shellSort(arr)
+  expect(res).toEqual([121, 169, 190])
+})