Bun's test runner supports Jest-style snapshot testing via .toMatchSnapshot().

import { test, expect } from "bun:test";

test("snapshot", () => {
  expect({ foo: "bar" }).toMatchSnapshot();
});

---

The first time this test is executed, Bun will write a snapshot file to disk in a directory called __snapshots__ that lives alongside the test file.

test
├── __snapshots__
│   └── snap.test.ts.snap
└── snap.test.ts

---

To regenerate snapshots, use the --update-snapshots flag.

bun test --update-snapshots

test/snap.test.ts:
✓ snapshot [0.86ms]

 1 pass
 0 fail
 snapshots: +1 added # the snapshot was regenerated
 1 expect() calls
Ran 1 tests across 1 files. [102.00ms]

---

See Docs > Test Runner > Snapshots for complete documentation on snapshots with the Bun test runner.