This can be very useful for setting up **resources** that you need to use for the whole app, and that are **shared** among requests, and/or that you need to **clean up** afterwards. For example, a database connection pool, or loading a shared machine learning model.

## Use Case

Let's start with an example **use case** and then see how to solve it with this.

Let's imagine that you have some **machine learning models** that you want to use to handle requests. 🤖

   * there's no way to assign a {@code @Nullable T} to a field {@code T foo;} and instruct the
   * analysis that that means "plain {@code T}" rather than the inferred type {@code @Nullable T}.
   * (Even if supported added {@code @NonNull}, that would not help, since the problem case
   * addressed by this method is the case in which {@code T} has parametric nullness -- and thus its
   * value may be legitimately {@code null}.)
   */

  /**
   * The largest power of two that can be represented as a signed {@code byte}.
   *
   * @since 10.0
   */
  public static final byte MAX_POWER_OF_TWO = 1 << 6;

  /**
   * Returns the {@code byte} value that is equal to {@code value}, if possible.
   *
   * @param value any value in the range of the {@code byte} type
   * @return the {@code byte} value that equals {@code value}

  /**
   * Returns a dispatcher that queues events that are posted reentrantly on a thread that is already
   * dispatching an event, guaranteeing that all events posted on a single thread are dispatched to
   * all subscribers in the order they are posted.
   *
   * <p>When all subscribers are dispatched to using a <i>direct</i> executor (which dispatches on

In the output, you can see that it shows the **PID** (process ID) of each process (it's just a number).

You can see that:

* The Gunicorn **process manager** starts with PID `19499` (in your case it will be a different number).
* Then it starts `Listening at: http://0.0.0.0:80`.
* Then it detects that it has to use the worker class at `uvicorn.workers.UvicornWorker`.

You probably want to test the external provider once, but not necessarily call it for every test that runs.

In this case, you can override the dependency that calls that provider, and use a custom dependency that returns a mock user, only for your tests.

### Use the `app.dependency_overrides` attribute

It means that **FastAPI** was specifically tested with the editors used by 80% of the Python developers. And as most of the other editors tend to work similarly, all its benefits should work for virtually all editors.

 *  * **Canceled:** the web socket connection failed. Messages that were successfully enqueued by
 *    either peer may not have been transmitted to the other.
 *
 * Note that the state progression is independent for each peer. Arriving at a gracefully-closed
 * state indicates that a peer has sent all of its outgoing messages and received all of its
 * incoming messages. But it does not guarantee that the other peer will successfully receive all of

    The correct place is:

    * In the key `content`, that has as value another JSON object (`dict`) that contains:
        * A key with the media type, e.g. `application/json`, that contains as value another JSON object, that contains:
            * A key `schema`, that has as the value the JSON Schema from the model, here's the correct place.

   * there's no way to assign a {@code @Nullable T} to a field {@code T foo;} and instruct the
   * analysis that that means "plain {@code T}" rather than the inferred type {@code @Nullable T}.
   * (Even if supported added {@code @NonNull}, that would not help, since the problem case
   * addressed by this method is the case in which {@code T} has parametric nullness -- and thus its
   * value may be legitimately {@code null}.)
   */