* earliest one wins. This applies to both executions scheduled with [TaskRunner.Queue.schedule] and
 * those implied by the returned execution delay.
 *
 * Cancellation
 * ------------
 *
 * Tasks may be canceled while they are waiting to be executed, or while they are executing.
 *
 * Canceling a task that is waiting to execute prevents that upcoming execution. Canceling a task

import org.junit.jupiter.api.Test;
import org.mockito.Mockito;

import static org.junit.jupiter.api.Assertions.assertThrows;

class SimplexTransferListenerTest {
    @Test
    void cancellation() throws InterruptedException {
        TransferListener delegate = new TransferListener() {
            @Override
            public void transferInitiated(TransferEvent event) throws TransferCancelledException {

 *
 * <p>This class has limited support for cancellation and other "early completions":
 *
 * <ul>
 *   <li>While calls to {@code submit} and {@code submitAsync} return a {@code Future} that can be
 *       cancelled, cancellation never propagates to a task that has started to run -- neither to
 *       the callable itself nor to any {@code Future} returned by an {@code AsyncCallable}.

Context timeouts are propagated, and a default timeout of 1 minute is added if none is specified.

There is no cancellation propagation for single payload requests.
When the context is canceled, the request will return at once with an appropriate error. 
However, the remote call will not see the cancellation - as can be seen from the 'missing' context on the handler.
The result will be discarded.

### Typed handlers

 *
 * <p>This class has limited support for cancellation and other "early completions":
 *
 * <ul>
 *   <li>While calls to {@code submit} and {@code submitAsync} return a {@code Future} that can be
 *       cancelled, cancellation never propagates to a task that has started to run -- neither to
 *       the callable itself nor to any {@code Future} returned by an {@code AsyncCallable}.

 * limitations under the License.
 */
package okhttp3

import okio.IOException

interface Callback {
  /**
   * Called when the request could not be executed due to cancellation, a connectivity problem or
   * timeout. Because networks can fail during an exchange, it is possible that the remote server
   * accepted the request before the failure.
   */
  fun onFailure(
    call: Call,

  /**
   * Tests that a canceled future throws a cancellation exception.
   *
   * <p>This method checks the cancel, isCancelled, and isDone methods.
   */
  public void testCanceledFutureThrowsCancellation() throws Exception {

    assertFalse(future.isDone());
    assertFalse(future.isCancelled());

    CountDownLatch successLatch = new CountDownLatch(1);

    // Run cancellation in a separate thread as an extra thread-safety test.

import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import javax.annotation.concurrent.GuardedBy;
import junit.framework.TestCase;

/** Tests for {@link AbstractFuture} with the cancellation cause system property set */
@AndroidIncompatible // custom classloading

public class AbstractFutureCancellationCauseTest extends TestCase {

  private ClassLoader oldClassLoader;

import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import javax.annotation.concurrent.GuardedBy;
import junit.framework.TestCase;

/** Tests for {@link AbstractFuture} with the cancellation cause system property set */
@AndroidIncompatible // custom classloading

public class AbstractFutureCancellationCauseTest extends TestCase {

  private ClassLoader oldClassLoader;

  }
}
```

This is implemented using `suspendCancellableCoroutine`
but uses the standard Dispatcher in OkHttp. This means
that by default Kotlin's Dispatchers are not used.

Cancellation if implemented sensibly in both directions.
Cancelling a coroutine scope, will cancel the call.
Cancelling a call, will throw a CancellationException