///

```Python hl_lines="7"
{!> ../../docs_src/request_forms/tutorial001.py!}
```

////

For example, in one of the ways the OAuth2 specification can be used (called "password flow") it is required to send a `username` and `password` as form fields.

The <abbr title="specification">spec</abbr> requires the fields to be exactly named `username` and `password`, and to be sent as form fields, not JSON.

				// The context of the lock is canceled, this can happen
				// if one lock lost quorum due to cluster instability
				// in that case, try to lock again.
				break keepLock
			case ld.lockContext <- lkctx:
				// Send the lock context to anyone asking for it
			}
		}
	}
}

func mergeContext(ctx1, ctx2 context.Context) (context.Context, context.CancelFunc) {
	ctx, cancel := context.WithCancel(context.Background())
	go func() {

			val:   0.61,
			label: labels[3],
		},
		{
			val:   0.79,
			label: labels[2],
		},
	}
	ticker := time.NewTicker(1 * time.Millisecond)
	defer ticker.Stop()
	for _, obs := range observations {
		// Send observations once every 1ms, to simulate delay between
		// observations. This is to test the channel based
		// synchronization used internally.
		select {
		case <-ticker.C:

```Python
app.dependency_overrides = {}
```

/// tip

If you want to override a dependency only during some tests, you can set the override at the beginning of the test (inside the test function) and reset it at the end (at the end of the test function).

	return nil
}

func (t *testLogger) IsOnline(ctx context.Context) bool {
	return t.current.Load() != nil
}

func (t *testLogger) Cancel() {
	t.current.Store(nil)
}

func (t *testLogger) Send(ctx context.Context, entry interface{}) error {
	tb := t.current.Load()
	var logf func(format string, args ...any)
	if tb != nil {
		tbb := *tb
		tbb.Helper()
		switch t.action.Load() {
		case errorMessage:

/// tip

Note that the test function is now `async def` instead of just `def` as before when using the `TestClient`.

///

Then we can create an `AsyncClient` with the app, and send async requests to it, using `await`.

{* ../../docs_src/async_tests/test_main.py hl[9:12] *}

This is the equivalent to:

```Python
response = client.get('/')
```

This includes, for example:

* Email notifications sent after performing an action:
    * As connecting to an email server and sending an email tends to be "slow" (several seconds), you can return the response right away and send the email notification in the background.
* Processing data:
    * For example, let's say you receive a file that must go through a slow process, you can return a response of "Accepted" (HTTP 202) and process the file in the background.

            }

            if ( log.isTraceEnabled() ) {
                log.trace("Sending NtTransNotifyChange for " + this.handle);
            }
            try {
                resp = th.send(req, resp, RequestParam.NO_TIMEOUT, RequestParam.NO_RETRY);
            }
            catch ( SmbException e ) {
                if ( e.getNtStatus() == 0xC0000120 ) {
                    // cancelled

        if (requestHeaders.name(i) == Header.TARGET_PATH_UTF8) {
          path = requestHeaders.value(i)
          break
        }
        i++
      }
      if (path == null) {
        // TODO: send bad request error
        throw AssertionError()
      }
      val file = File(baseDirectory.toString() + path)
      if (file.isDirectory) {
        serveDirectory(stream, file.listFiles()!!)

///

## About HTTP status codes

/// note

If you already know what HTTP status codes are, skip to the next section.

///

In HTTP, you send a numeric status code of 3 digits as part of the response.

These status codes have a name associated to recognize them, but the important part is the number.

In short: