[Node.js]jestでテストを書く

package.json

{
  "devDependencies": {
    "jest": "^26.4.2"
  }
}

sum.js

module.exports = function sum(a, b) {
  return a + b;
};

sum.test.js

const sum = require("./sum");

test("adds 1 + 2 to equal 3", () => {
  expect(sum(1, 2)).toBe(3);
});

テスト実行

$ npx jest
 PASS  ./sum.test.js
  ✓ adds 1 + 2 to equal 3 (1 ms)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        1.271 s
Ran all test suites.