# Concurrency

`import { Concurrency } from "destack:test";`

Test scheduler concurrency mode.

```ds title="Concurrency"
export enum Concurrency {
    Auto = 1,
    Serial = 2,
    Concurrent = 3,
}
```

[language/library/src/test/options.ds:17:24](https://github.com/destack-sh/destack/blob/main/language/library/src/test/options.ds#L17-L24)

## Variants

### `Auto = 1`

Let the runner decide.

### `Serial = 2`

Run cases one at a time.

### `Concurrent = 3`

Run independent cases concurrently.