# set-env Action

Used in [FLAT tests](https://sevenval.gitbook.io/flat/reference/testing) to change the environment of the FLAT app under test.

Normally, env vars are set on server start-up and are immutable later on. They are available in the pre-defined variable [`$env`](https://sevenval.gitbook.io/flat/variables#predefined-variables).

The action allows to override variables in the `$env` structure for testing purposes.

## Syntax

```markup
<set-env>
{
  "VAR_NAME": "VALUE",
  "BUILD_TIME": {{ unixtime() - 3600 }}
}
</set-env>
```

The action argument is a JSON Object. The property values should be of type string.

As env vars from the system (shell or `docker`) can only be strings, numeric or boolean values are cast to their *string representation*.

If the value is `null`, the env var is unset.

The action argument may be a [JSON template](https://sevenval.gitbook.io/flat/reference/templating).

## See also

* [`$env`](https://sevenval.gitbook.io/flat/variables#predefined-variables) (reference)
* [Using Env Vars](https://sevenval.gitbook.io/flat/cookbook/envvars) (cookbook)
* [Testing](https://sevenval.gitbook.io/flat/reference/testing) (reference)


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