# toYamlSnapshot (/docs/matchers/to-yaml-snapshot)



Signature [#signature]

```ts
toYamlSnapshot(options?: SnapYamlOptions<T>): Promise<void>
```

Description [#description]

Serializes the received value to a YAML string and writes it to a snapshot file.
On subsequent runs the file content is diffed — the test fails if it differs.

Before serialization, the value is passed through the configured **filters** and **redactions**
pipeline:

1. Clone input value.
2. Apply each filter in order.
3. Apply each redaction in order.
4. Serialize with `yaml.stringify(value, { indent })`.
5. Write to snapshot file via `toMatchFileSnapshot`.

Defaults applied automatically [#defaults-applied-automatically]

| Concern           | Default behaviour                                           |
| ----------------- | ----------------------------------------------------------- |
| `undefined` props | Removed by `UndefinedFilter`                                |
| `Date` values     | Replaced with `[Date_1]`, `[Date_2]`, … by `ValueRedaction` |

Options [#options]

```ts
type SnapYamlOptions<T> = {
  dir?: string;
  name?: string;
  fileExtension?: string;
  args?: any[];
  filters?: (Selector<T> | Filter<T>)[];
  redactions?: Redaction<T>[];
  indent?: number;
};
```

| Option          | Default                                  | Description                                                           |
| --------------- | ---------------------------------------- | --------------------------------------------------------------------- |
| `dir`           | `"./snapshots"`                          | Directory relative to the test file                                   |
| `name`          | current test name                        | Slug used as the base filename                                        |
| `fileExtension` | none                                     | Extension appended to the file                                        |
| `args`          | `[]`                                     | Extra segments for parametric snapshots                               |
| `filters`       | `[new UndefinedFilter()]`                | Filters applied before serialization — see [Filters](/docs/filters)   |
| `redactions`    | `[new ValueRedaction(isDate, "[Date]")]` | Redactions applied after filters — see [Redactions](/docs/redactions) |
| `indent`        | `2`                                      | Spaces used for YAML indentation                                      |

Examples [#examples]

Basic usage [#basic-usage]

```ts
import { describe, expect, test } from "vitest";

test("user object", async () => {
  const user = { id: 1, name: "Alice", createdAt: new Date() };
  await expect(user).toYamlSnapshot();
  // writes: ./snapshots/user-object
  // id: 1
  // name: Alice
  // createdAt: "[Date_1]"
});
```

Custom file extension [#custom-file-extension]

```ts
test("config", async () => {
  await expect(config).toYamlSnapshot({ fileExtension: "yaml" });
  // writes: ./snapshots/config.yaml
});
```

Parameterized snapshots [#parameterized-snapshots]

```ts
test.each([10, 50, 100])("pagination page-size %i", async (pageSize) => {
  const result = await fetchUsers({ pageSize });
  await expect(result).toYamlSnapshot({ args: [pageSize] });
  // writes: ./snapshots/pagination-page-size-10
  // writes: ./snapshots/pagination-page-size-50
  // writes: ./snapshots/pagination-page-size-100
});
```

Custom filters [#custom-filters]

```ts
import { NullFilter, ExcludeFilter } from "vitest-snap";

test("filtered snapshot", async () => {
  await expect(data).toYamlSnapshot({
    filters: [new NullFilter(), new ExcludeFilter(".internalId")],
  });
});
```

Custom redactions [#custom-redactions]

```ts
import { ReplacedRedaction } from "vitest-snap";

test("redacted snapshot", async () => {
  await expect(user).toYamlSnapshot({
    redactions: [new ReplacedRedaction(".password", "[REDACTED]")],
  });
});
```

Include only specific fields [#include-only-specific-fields]

```ts
import { IncludeFilter } from "vitest-snap";

test("public fields only", async () => {
  await expect(user).toYamlSnapshot({
    filters: [".id", ".name", ".email"],
  });
});
```