Let's look at how we can make that work.

## pytest.mark.anyio { #pytest-mark-anyio }

If we want to call asynchronous functions in our tests, our test functions have to be asynchronous. AnyIO provides a neat plugin for this, that allows us to specify that some test functions are to be called asynchronously.

## HTTPX { #httpx }

 * asynchronous handling, message chaining, cancellation, and timeout management.
 *
 * @author mbechler
 */
public interface CommonServerMessageBlockRequest extends CommonServerMessageBlock, Request {

    /**
     * Checks if the request will be handled asynchronously.
     *
     * @return request was handled asynchronously
     */
    boolean isResponseAsync();

    /**

    }

    /**
     * Indexes a document asynchronously.
     *
     * @param request the index request
     * @return a future for the index response
     */
    @Override
    public ActionFuture<IndexResponse> index(final IndexRequest request) {
        return client.index(request);
    }

    /**
     * Indexes a document asynchronously with a callback.
     *

 *
 * All event methods must execute fast, without external locking, cannot throw exceptions,
 * attempt to mutate the event parameters, or be reentrant back into the client.
 * Any IO - writing to files or network should be done asynchronously.
 */
internal abstract class ConnectionListener {
  /**
   * Invoked as soon as a call causes a connection to be started.
   */
  open fun connectStart(
    route: Route,
    call: Call,
  ) {}

   * calls returns to zero).
   *
   * Note: The time at which a [call][Call] is considered idle is different depending on whether it
   * was run [asynchronously][Call.enqueue] or [synchronously][Call.execute]. Asynchronous calls
   * become idle after the [onResponse][Callback.onResponse] or [onFailure][Callback.onFailure]
   * callback has returned. Synchronous calls become idle once [execute()][Call.execute] returns.

   * executor}.
   *
   * @param listener the backing listener
   * @param executor the executor with which removal notifications are asynchronously executed
   */
  public static <K, V> RemovalListener<K, V> asynchronous(
      RemovalListener<K, V> listener, Executor executor) {
    checkNotNull(listener);
    checkNotNull(executor);
    return (RemovalNotification<K, V> notification) ->

package com.google.common.util.concurrent;

import com.google.common.annotations.GwtCompatible;
import java.util.concurrent.Future;
import org.jspecify.annotations.Nullable;

/**
 * Transforms a value, possibly asynchronously. For an example usage and more information, see
 * {@link Futures#transformAsync(ListenableFuture, AsyncFunction, Executor)}.
 *
 * @author Chris Povirk
 * @since 11.0
 */
@GwtCompatible

package com.google.common.util.concurrent;

import com.google.common.annotations.GwtCompatible;
import java.util.concurrent.Future;
import org.jspecify.annotations.Nullable;

/**
 * Computes a value, possibly asynchronously. For an example usage and more information, see {@link
 * Futures.FutureCombiner#callAsync(AsyncCallable, java.util.concurrent.Executor)}.
 *

    // Already connected. Return it immediately.
    if (plan.isReady) return ConnectResult(plan)

    // Already failed? Return it immediately.
    if (plan is FailedPlan) return plan.result

    // Connect TCP asynchronously.
    tcpConnectsInFlight += plan
    val taskName = "$okHttpName connect ${routePlanner.address.url.redact()}"
    taskRunner.newQueue().schedule(
      object : Task(taskName) {

import java.util.concurrent.Future;
import org.jspecify.annotations.Nullable;

/**
 * A callback for accepting the results of a {@link java.util.concurrent.Future} computation
 * asynchronously.
 *
 * <p>To attach to a {@link ListenableFuture} use {@link Futures#addCallback}.
 *
 * @author Anthony Zana
 * @since 10.0
 */
@GwtCompatible
public interface FutureCallback<V extends @Nullable Object> {