add unit test cases

src/App.tsx

@@ -1,4 +1,4 @@
-import { useState, type DOMAttributes } from 'react';
+import { useState } from 'react';
 import getSum, { defaultSeprator } from "./stringCalculator"
 
 const App = () => {

src/stringCalculator.test.ts

@@ -1,18 +1,41 @@
-// Test cases possible
-
-/**
- * 1. ""
- * 2. "12"
- * 3. "1,2"
- * 4. "1,2,3,4"
- * 5. "1,2,3,4"  , "-" => custom limiter
- * 6. "1,2,-3,4" => negative number
- * 7. "1 , 2 , 3  , 4" => handle trailing space cases
- * 8. "1, 2, - 3, 4" => any one number is not a valid number
- * 9. 1--2-3-4 => throw error
- */
-
-/**
- * limiter input if it is empty then what does it do
- * it the 
- */
+import {describe, test, expect } from 'vitest'
+import getStringSum from "./stringCalculator"
+
+ describe('getStringSum', () => {
+  test('returns 0 for empty string', () => {
+    expect(getStringSum("")).toBe(0)
+  })
+
+  test('returns the number testself for a single number string', () => {
+    expect(getStringSum("12")).toBe(12)
+  })
+
+  test('returns sum for comma-separated numbers', () => {
+    expect(getStringSum("1,2")).toBe(3)
+    expect(getStringSum("1,2,3,4")).toBe(10)
+  })
+
+  test('handles custom separator', () => {
+    expect(getStringSum("1-2-3-4", "-")).toBe(10)
+  })
+
+  test('handles negative numbers', () => {
+    expect(getStringSum("1,2,-3,4")).toBe(4)
+  })
+
+  test('handles extra spaces', () => {
+    expect(getStringSum("1 , 2 , 3  , 4")).toBe(10)
+  })
+
+  test('throws error if any number is invalid due to internal spaces', () => {
+    expect(() => getStringSum("1, 2, - 3, 4")).toThrowError(
+      new Error("input is not a list of valid number")
+    )
+  })
+
+  test('throws error for invalid input like 1--2-3-4', () => {
+    expect(() => getStringSum("1--2-3-4", "-")).toThrowError(
+      new Error("input is not a list of valid number")
+    )
+  })
+})