# Async Tests { #async-tests }

You have already seen how to test your **FastAPI** applications using the provided `TestClient`. Up to now, you have only seen how to write synchronous tests, without using `async` functions.

          parentBuilder) {
    List<TestSuite> derived = super.createDerivedSuites(parentBuilder);
    // TODO(cpovirk): consider using this approach (derived suites instead of extension) in
    // ListTestSuiteBuilder, etc.?
    derived.add(
        MapTestSuiteBuilder.using(new MapGenerator<K, V>(parentBuilder.getSubjectGenerator()))
            .withFeatures(parentBuilder.getFeatures())

If you don't declare a response model, FastAPI will use the `jsonable_encoder` explained in [JSON Compatible Encoder](../tutorial/encoder.md) and put it in a `JSONResponse`.

You could also create a `JSONResponse` directly and return it.

/// tip

 * {@snippet :
 * // won't work
 * TreeTraverser<NodeType> traverser = node -> node.getChildNodes();
 * }
 *
 * Instead, you can pass a lambda expression to the {@code using} factory method:
 *
 * {@snippet :
 * TreeTraverser<NodeType> traverser = TreeTraverser.using(node -> node.getChildNodes());
 * }
 *
 * @author Louis Wasserman
 * @since 15.0

## Introduction

This chart bootstraps MinIO Cluster on [Kubernetes](http://kubernetes.io) using the [Helm](https://helm.sh) package manager.

   * little-endian byte order.
   *
   * @throws IOException if an I/O error occurs
   */
  @Override
  public void writeChar(int v) throws IOException {
    writeShort(v);
  }

  /**
   * Writes a {@code String} as specified by {@link DataOutputStream#writeChars(String)}, except
   * each character is written using little-endian byte order.
   *

    return emptySet();
  }

  @SuppressWarnings("EmptyList") // We specifically want to test emptyList()
  public Test testsForEmptyList() {
    return ListTestSuiteBuilder.using(
            new TestStringListGenerator() {
              @Override
              public List<String> create(String[] elements) {
                return emptyList();
              }
            })

    return emptySet();
  }

  @SuppressWarnings("EmptyList") // We specifically want to test emptyList()
  public Test testsForEmptyList() {
    return ListTestSuiteBuilder.using(
            new TestStringListGenerator() {
              @Override
              public List<String> create(String[] elements) {
                return emptyList();
              }
            })

        SetTestSuiteBuilder.using(new ImmutableSetWithBadHashesGenerator())
            .named(ImmutableSetTest.class.getName() + ", with bad hashes")
            .withFeatures(
                CollectionSize.ANY,
                CollectionFeature.KNOWN_ORDER,
                CollectionFeature.ALLOWS_NULL_QUERIES)
            .createTestSuite());

    suite.addTest(
        SetTestSuiteBuilder.using(new DegeneratedImmutableSetGenerator())

You can also connect using any S3-compatible tool, such as the MinIO Client `mc` commandline tool:

```sh
mc alias set local http://localhost:9000 minioadmin minioadmin
mc admin info local
```

See [Test using MinIO Client `mc`](#test-using-minio-client-mc) for more information on using the `mc` commandline tool.