toMatchJsonFile

Asserts that a value matches a JSON file snapshot. The value is serialized to JSON and compared to a stored validation file. Supports retries when a callback function is provided as the actual value.

Usage

Static Snapshot

test("matches page title ultimately", async () => {
  await page.setContent("<title>Page Title</title>");

  await expect({
    title: await page.title(),
  }).toMatchJsonFile();
});

Output (matches_page_title.json):

{
  "title": "Page Title"
}

Repeatable Snapshot

When passing a callback function as actual value, the snapshot will be retried until it matches the stored validation file:

test("matches page title eventually", async () => {
  await page.setContent("<title>Page Title</title>");

  await expect(async () => ({
    title: await page.title(),
  })).toMatchJsonFile();
});

undefined Object Properties

By default, object properties with an undefined value are omitted from the snapshot. Set includeUndefinedObjectProperties to true to include them:

test("includes undefined properties", async () => {
  await expect({ name: "Alice", age: undefined }).toMatchJsonFile({
    includeUndefinedObjectProperties: true,
  });
});

Output (includes_undefined_properties.json):

{
  "name": "Alice",
  "age": {
    "$type": "undefined"
  }
}

Options

Option	Default Value	Description
includeUndefinedObjectProperties	false	Serializes undefined properties in objects. By default, they are omitted.
name	undefined	Unique name of the file snapshot. Used to distinguish multiple file snapshots within the same test. See Named Snapshots.
normalizers	[]	Custom normalizers to apply before serialization. See Normalization of Snapshots.
timeout	expect timeout	Retries the snapshot until it passes or the timeout is reached. Only applies when a callback is passed. See Snapshot Retries.
updateDelay	250	Delay in ms before a repeatable snapshot is created in update mode. See See Snapshot Retries.
resolveFilePath	resolveNameAsFile	Custom resolver for the file path used to store snapshots. See Named Snapshots.