---
title: YAML
description: YAML snapshots are stored as written: comments and layout survive, nothing is re-emitted. They are compared as trees, the same way as JSON, with differences...
url: https://docs-v3-preview.elastic.dev/formats/yaml
---

# YAML
```csharp
using Nullean.Snapshots.Yaml;

config.Should().MatchYamlSnapshot();
config.Should().BeYaml("items: [{id: 1}]");
```

YAML snapshots are stored **as written**: comments and layout survive, nothing is re-emitted. They are compared as
trees, the same way as [JSON](https://docs-v3-preview.elastic.dev/formats/json), with differences pointing at line and column in the verified file:
```text
YAML did not match snapshot: tests/App.Tests/.snapshots/ConfigTests/Renders.verified.yml
3 difference(s):
$.items[0].name   expected "kibana"   actual "Kibana"   (verified.yml:3:11)
$.items[1]        missing in actual   (verified.yml:5:5)
$.meta.extra      unexpected in actual
```


## Typing

Plain scalars are typed with the **YAML 1.2 core schema**, not 1.1:

| Written                               | Is                                     |
|---------------------------------------|----------------------------------------|
| `true`, `True`, `TRUE`, `false`, …    | a boolean                              |
| `yes`, `no`, `on`, `off`              | a string                               |
| `null`, `Null`, `NULL`, `~`, nothing  | null                                   |
| `42`, `+1`, `017`                     | a decimal integer                      |
| `0o17`, `0x1F`                        | an integer, equal to its decimal value |
| `1_000`, `0b101`                      | a string                               |
| `1.5`, `1e3`, `.inf`, `-.Inf`, `.nan` | a float                                |
| `"true"`, `'1'`, block scalars        | a string                               |

`!!str`, `!!int`, `!!float`, `!!bool` and `!!null` tags apply; local tags such as `!ref` are typed as if they were not
there.

## Anchors and merge keys

Aliases are the anchored value, and `<<` merge keys are resolved: explicit keys win over merged ones, and of several
merged mappings the first wins. A YAML snapshot with anchors compares equal to the same data written out in full.
A stream of several documents compares document by document, with paths such as `$doc[1].name`.
For a short value there is `MatchInlineYamlSnapshot`, which keeps the expected value in the test as a literal: see [inline snapshots](https://docs-v3-preview.elastic.dev/formats/inline).