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docs: Describe random string case in snapshot testing #12501

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Feb 26, 2022
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docs: Describe random string case in snapshot testing #12501

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docs: Describe random string case in snapshot testing
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Expand Up @@ -210,6 +210,22 @@ Object {
`;
```

:::tip

If the case concerns a string not an object then you need to replace random part of that string on your own before testing the snapshot.
You can use for that e.g. [`replace()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace) and [regular expressions](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions).

```javascript
const randomNumber = Math.round(Math.random() * 100);
const stringWithRandomData = `<div id="${randomNumber}">Lorem ipsum</div>`;
const stringWithConstantData = stringWithRandomData.replace(/id="\d+"/, 123);
expect(stringWithConstantData).toMatchSnapshot();
```

Another way is to [mock](MockFunctions.md) the library responsible for generating the random part of the code you're snapshotting.

:::

## Best Practices

Snapshots are a fantastic tool for identifying unexpected interface changes within your application – whether that interface is an API response, UI, logs, or error messages. As with any testing strategy, there are some best-practices you should be aware of, and guidelines you should follow, in order to use them effectively.
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