[API reference](https://evolu.dev/docs/api-reference) › [@evolu/common](https://evolu.dev/docs/api-reference/common) › [WebSocket](https://evolu.dev/docs/api-reference/common/WebSocket) › testSetupWebSocket

```ts
function testSetupWebSocket(url: string): Promise<TestSetupWebSocket>;
```

Defined in: [packages/common/src/WebSocket.ts:538](https://github.com/evoluhq/evolu/blob/dd96d79f1dbe9a49fa12ce8e0aa7d3d0177795ca/packages/common/src/WebSocket.ts#L538)

Opens a native [WebSocket](https://evolu.dev/docs/api-reference/common/WebSocket/interfaces/WebSocket) and returns [TestSetupWebSocket](https://evolu.dev/docs/api-reference/common/WebSocket/interfaces/TestSetupWebSocket).