toMatchJsonFile

Asserts that a value matches a JSON file snapshot. The value is serialized to JSON and compared to a stored validation file.

Usage

test("value is expected value", () => {
  expect({ value: "expected value" }).toMatchJsonFile();
});

Output:

value_is_expected_value.json

{
  "value": "expected value"
}

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", () => {
  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.
resolveFilePath	resolveNameAsFile	Custom resolver for the file path used to store snapshots. See File Path Resolvers.