assertEquals(0, stats.getTotalChannels());
    }

    @Test
    @DisplayName("createChannelTransport should fail with null addresses")
    void testCreateChannelTransportWithNullAddresses() {
        // Use reflection to access private method for testing
        Exception exception = assertThrows(Exception.class, () -> {
            java.lang.reflect.Method method =

        // First call should read the file
        NbtAddress result1 = lmhosts.getByName("TESTHOST", mockContext);
        assertNotNull(result1);

        // Second call should use cached data (file not modified)
        NbtAddress result2 = lmhosts.getByName("TESTHOST", mockContext);
        assertNotNull(result2);
        assertEquals(result1, result2);
    }

    @Test

///

/// info

In this example we use invented custom headers `X-Key` and `X-Token`.

But in real cases, when implementing security, you would get more benefits from using the integrated [Security utilities (the next chapter)](../security/index.md){.internal-link target=_blank}.

///

## Dependencies errors and return values { #dependencies-errors-and-return-values }

You can use the same dependency *functions* you use normally.

# Form Data { #form-data }

When you need to receive form fields instead of JSON, you can use `Form`.

/// info

To use forms, first install <a href="https://github.com/Kludex/python-multipart" class="external-link" target="_blank">`python-multipart`</a>.

Make sure you create a [virtual environment](../virtual-environments.md){.internal-link target=_blank}, activate it, and then install it, for example:

```console
$ pip install python-multipart
```

### Using your local FastAPI

If you create a Python file that imports and uses FastAPI, and run it with the Python from your local environment, it will use your cloned local FastAPI source code.

And if you update that local FastAPI source code when you run that Python file again, it will use the fresh version of FastAPI you just edited.

That way, you don't have to "install" your local version to be able to test every change.

/*
 * Copyright (C) 2014 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

        .put(path.asRequestBody(fileSystem, MEDIA_TYPE_JSON))
        .build()

    client.newCall(request).execute().use { response ->
      if (!response.isSuccessful) throw IOException("Unexpected code $response")

      fileSystem.sink(path).use {
        response.body.source().readAll(it)
      }

      println(fileSystem.source(path).buffer().readUtf8())
    }
  }

  companion object {

 * [system DNS service][SYSTEM], which is the default. Some applications may provide their own
 * implementation to use a different DNS server, to prefer IPv6 addresses, to prefer IPv4 addresses,
 * or to force a specific known IP address.
 *
 * Implementations of this interface must be safe for concurrent use.
 */
fun interface Dns {
  /**

We can use **OAuth2** to build that with **FastAPI**.

But let's save you the time of reading the full long specification just to find those little pieces of information you need.

Let's use the tools provided by **FastAPI** to handle security.

## How it looks { #how-it-looks }

/// tip

This is probably not as important or necessary if you use `Annotated`.

///

Let's say that you want to declare the query parameter `q` as a required `str`.

And you don't need to declare anything else for that parameter, so you don't really need to use `Query`.

But you still need to use `Path` for the `item_id` path parameter. And you don't want to use `Annotated` for some reason.