init jest

src/__tests__/index.test.ts

@@ -0,0 +1,10 @@
+import { sum } from './mocks/sum';
+import { describe, test, expect } from '@jest/globals';
+
+describe('Тесты на функцию sum', () => {
+  test('1 + 2 = 3', () => {
+    const result = sum(1, 2);
+
+    expect(result).toBe(3);
+  });
+});

src/__tests__/mocks/sum.ts

@@ -0,0 +1,3 @@
+export function sum(a, b) {
+  return a + b;
+}