But if you need to access variables and objects from the same **FastAPI** app, or you need to perform small background tasks (like sending an email notification), you can simply just use `BackgroundTasks`.

## Recap { #recap }

  fun sleep(durationNanos: Long) {
    taskRunner.withLock {
      val sleepUntil = nanoTime + durationNanos
      yieldUntil { nanoTime >= sleepUntil }
    }
  }

  /**
   * Artificially stall until manually resumed by the test thread with [runTasks]. Use this to
   * simulate races in tasks that doesn't have a deterministic sequence.
   */
  fun yield() {
    taskRunner.assertLockNotHeld()

Keep in mind that this means that the whole contents will be stored in memory. This will work well for small files.

But there are several cases in which you might benefit from using `UploadFile`.

## File Parameters with `UploadFile` { #file-parameters-with-uploadfile }

Define a file parameter with a type of `UploadFile`:

import javax.net.ssl.X509TrustManager
import mockwebserver3.SocketEffect.CloseSocket
import mockwebserver3.SocketEffect.CloseStream
import mockwebserver3.SocketEffect.ShutdownConnection
import mockwebserver3.SocketEffect.Stall
import mockwebserver3.internal.DEFAULT_REQUEST_LINE_HTTP_1
import mockwebserver3.internal.DEFAULT_REQUEST_LINE_HTTP_2
import mockwebserver3.internal.MockWebServerSocket
import mockwebserver3.internal.RecordedRequest

CMD ["fastapi", "run", "app/main.py", "--port", "80"]
```

⛔️ **Shell**-форма:

```Dockerfile
# ⛔️ Не делайте так
CMD fastapi run app/main.py --port 80
```

Обязательно используйте **exec**-форму, чтобы FastAPI мог корректно завершаться и чтобы срабатывали [события lifespan](../advanced/events.md).

    @Test
    @DisplayName("Should throw exception when buffer too small for path")
    void testBufferTooSmallForPath() throws Exception {
        // Given
        String longPath = "\\\\server\\very_long_share_name_that_exceeds_buffer";
        Smb2TreeConnectRequest req = new Smb2TreeConnectRequest(mockConfig, longPath);
        byte[] smallBuffer = new byte[20]; // Too small for header + path

        // When & Then

* IDE warnings become more accurate, reducing warnings fatigue.
* Public API nullability annotations become closer to reality.
* Java compilation of Gradle code suffers from small performance penalty (up to 10%).
* Time has to be allocated to clean up existing projects.
* One has to write NullAway-conformant code even when hacking.
* Some patterns used to satisfy NullAway can be slightly more verbose.

        }
    }

    private static List<String> filesFromMerge(String commit) throws IOException, InterruptedException, ExecutionException {
        // Git revision range syntax is part of git, not the shell; pass as-is.
        return getStdoutLines(new String[] {"git", "diff", "--name-only", commit + "^1.." + commit});
    }

  /** Default size of a compact hash-based collection. */
  static final int DEFAULT_SIZE = 3;

  /**
   * Minimum size of the hash table of a compact hash-based collection. Because small hash tables
   * use a byte[], any smaller size uses the same amount of memory due to object padding.
   */
  private static final int MIN_HASH_TABLE_SIZE = 4;

        data[7] = (byte) (high >> 24);

        PacDataInputStream pdis = createInputStream(data);
        Date date = pdis.readFiletime();
        assertNotNull(date);
        // Allow for a small difference due to precision loss
        assertEquals(time / 1000, date.getTime() / 1000);

        // Test with null date (0x7fffffff ffffffff)