---
title: tests
sidebarTitle: tests
---

# `fastmcp.utilities.tests`

## Functions

### `temporary_settings` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/tests.py#L24" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
temporary_settings(**kwargs: Any)
```


Temporarily override FastMCP setting values.

**Args:**
- `**kwargs`: The settings to override, including nested settings.


### `run_server_in_process` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/tests.py#L75" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
run_server_in_process(server_fn: Callable[..., None], *args: Any, **kwargs: Any) -> Generator[str, None, None]
```


Context manager that runs a FastMCP server in a separate process and
returns the server URL. When the context manager is exited, the server process is killed.

**Args:**
- `server_fn`: The function that runs a FastMCP server. FastMCP servers are
not pickleable, so we need a function that creates and runs one.
- `*args`: Arguments to pass to the server function.
- `provide_host_and_port`: Whether to provide the host and port to the server function as kwargs.
- `host`: Host to bind the server to (default\: "127.0.0.1").
- `port`: Port to bind the server to (default\: find available port).
- `**kwargs`: Keyword arguments to pass to the server function.

**Returns:**
- The server URL.


### `run_server_async` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/tests.py#L143" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
run_server_async(server: FastMCP, port: int | None = None, transport: Literal['http', 'streamable-http', 'sse'] = 'http', path: str = '/mcp', host: str = '127.0.0.1') -> AsyncGenerator[str, None]
```


Start a FastMCP server as an asyncio task for in-process async testing.

This is the recommended way to test FastMCP servers. It runs the server
as an async task in the same process, eliminating subprocess coordination,
sleeps, and cleanup issues.

**Args:**
- `server`: FastMCP server instance
- `port`: Port to bind to (default\: find available port)
- `transport`: Transport type ("http", "streamable-http", or "sse")
- `path`: URL path for the server (default\: "/mcp")
- `host`: Host to bind to (default\: "127.0.0.1")


## Classes

### `HeadlessOAuth` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/tests.py#L225" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>


OAuth provider that bypasses browser interaction for testing.

This simulates the complete OAuth flow programmatically by making HTTP requests
instead of opening a browser and running a callback server. Useful for automated testing.


**Methods:**

#### `redirect_handler` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/tests.py#L238" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
redirect_handler(self, authorization_url: str) -> None
```

Make HTTP request to authorization URL and store response for callback handler.


#### `callback_handler` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/tests.py#L244" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
callback_handler(self) -> tuple[str, str | None]
```

Parse stored response and return (auth_code, state).

