.build());
        Mockito.when(context.getUserProperty("revision")).thenReturn("therev");
        Mockito.when(context.getUserProperty("sha1")).thenReturn("thesha");
        Model expected = new Model(org.apache.maven.api.model.Model.newBuilder()
                .version("therev-thesha")
                .build());
        Model actual = transform(initial);

When building web APIs with FastAPI, if there's an error in our code, FastAPI will normally contain it to the single request that triggered the error. 🛡

The client will get a **500 Internal Server Error** for that request, but the application will continue working for the next requests instead of just crashing completely.

### Bigger Errors - Crashes

The **good news** is that with each different strategy there's a way to cover all of the deployment concepts. 🎉

Let's review these **deployment concepts** in terms of containers:

* HTTPS
* Running on startup
* Restarts

But there could be cases where you want to be able to set parameters on the dependency, without having to declare many different functions or classes.

Let's imagine that we want to have a dependency that checks if the query parameter `q` contains some fixed content.

But we want to be able to parameterize that fixed content.

## A "callable" instance

///

### Format the code

There is a script that you can run that will format and clean all your code:

<div class="termy">

```console
$ bash scripts/format.sh
```

</div>

It will also auto-sort all your imports.

## Tests

There is a script that you can run locally to test all the code and generate coverage reports in HTML:

* go to the parent package (the directory `app/`)...
* then go to the parent of that package (there's no parent package, `app` is the top level 😱)...
* and in there, find the module `dependencies` (the file at `app/dependencies.py`)...
* and from it, import the function `get_token_header`.

Hiding your documentation user interfaces in production *shouldn't* be the way to protect your API.

That doesn't add any extra security to your API, the *path operations* will still be available where they are.

If there's a security flaw in your code, it will still exist.

{!> ../../docs_src/query_params_str_validations/tutorial009.py!}
```

////

## Deprecating parameters

Now let's say you don't like this parameter anymore.

You have to leave it there a while because there are clients using it, but you want the docs to clearly show it as <abbr title="obsolete, recommended not to use it">deprecated</abbr>.

Then pass the parameter `deprecated=True` to `Query`:

    start();
  }

  // Thread.stop() is okay because all threads started by a test are dying at the end of the test,
  // so there is no object state put at risk by stopping the threads abruptly. In some cases a test
  // may put a thread into an uninterruptible operation intentionally, so there is no other way to
  // clean up these threads.
  @SuppressWarnings("deprecation")
  @Override
  public void tearDown() throws Exception {
    stop();

    start();
  }

  // Thread.stop() is okay because all threads started by a test are dying at the end of the test,
  // so there is no object state put at risk by stopping the threads abruptly. In some cases a test
  // may put a thread into an uninterruptible operation intentionally, so there is no other way to
  // clean up these threads.
  @SuppressWarnings("deprecation")
  @Override
  public void tearDown() throws Exception {
    stop();