Add Merge Sort test

Author: LyangHiga

src/sort/mergeSort.test.ts

@@ -0,0 +1,15 @@
+import mergeSort from "./mergeSort";
+
+describe("Test for Merge Sort", () => {
+  test("testing if MS sort random array", () => {
+    const nTimes = 100;
+    for (let i = 0; i < nTimes; i++) {
+      const arr = Array.from({ length: 100 }, () =>
+        Math.floor(Math.random() * 1000)
+      );
+      const sortedArr = mergeSort(arr);
+      const jsSortedArr = arr.slice().sort((a, b) => a - b);
+      expect(sortedArr).toEqual(jsSortedArr);
+    }
+  });
+});

src/sort/mergeSort.ts

@@ -64,4 +64,4 @@ const mergeSort = (arr: number[]): number[] => {
   return mergeIdx(mergeSort(left), mergeSort(right));
 };
 
-export = mergeSort;
+export default mergeSort;