verify(true);
  }

  public void testVerify_simple_failure() {
    try {
      verify(false);
      fail();
    } catch (VerifyException expected) {
    }
  }

  public void testVerify_simpleMessage_success() {
    verify(true, "message");
  }

  public void testVerify_simpleMessage_failure() {
    try {
      verify(false, "message");
      fail();

    @Nullable private String value = null;
    @Nullable private Throwable failure = null;
    private boolean wasCalled = false;

    MockCallback(String expectedValue) {
      this.value = expectedValue;
    }

    public MockCallback(Throwable expectedFailure) {
      this.failure = expectedFailure;
    }

    @Override
    public synchronized void onSuccess(String result) {

   * reading, such as an {@code InputStream}. Unlike with writable resources, there's no chance that
   * a failure that occurs when closing the stream indicates a meaningful problem such as a failure
   * to flush all bytes to the underlying resource.
   *
   * @param inputStream the input stream to be closed, or {@code null} in which case this method
   *     does nothing

   *   try {
   *     foo.bar();
   *   } catch (BarException | RuntimeException | Error t) {
   *     failure = t;
   *   }
   * }
   * if (failure != null) {
   *   throwIfInstanceOf(failure, BarException.class);
   *   throwIfUnchecked(failure);
   *   throw new AssertionError(failure);
   * }
   * </pre>
   *
   * @since 20.0
   */
  @GwtIncompatible // Class.cast, Class.isInstance

   *   try {
   *     foo.bar();
   *   } catch (BarException | RuntimeException | Error t) {
   *     failure = t;
   *   }
   * }
   * if (failure != null) {
   *   throwIfInstanceOf(failure, BarException.class);
   *   throwIfUnchecked(failure);
   *   throw new AssertionError(failure);
   * }
   * </pre>
   *
   * @since 20.0
   */
  @GwtIncompatible // Class.cast, Class.isInstance

 *     Guava 27.0
 */
public final class InternalFutures {
  /**
   * Usually returns {@code null} but, if the given {@code Future} has failed, may <i>optionally</i>
   * return the cause of the failure. "Failure" means specifically "completed with an exception"; it
   * does not include "was cancelled." To be explicit: If this method returns a non-null value,
   * then:
   *
   * <ul>

     *
     * - _shouldn't_ be null, so we don't annotate it with @Nullable
     *
     * - _can_ be null without causing a runtime failure (because we don't want the interesting
     *   details of precondition failure to be hidden by an exception we throw about an unexpectedly
     *   null _failure message_)
     *
     * That combination upsets NullPointerTester, which wants any call that passes null for a

          // misconfigured mock. Try to switch to Failure.
          Failure failure;
          try {
            failure = new Failure(t);
          } catch (Exception | Error oomMostLikely) { // sneaky checked exception
            failure = Failure.FALLBACK_INSTANCE;
          }

  }

  public void testTrustedGetFailure_Failed() {
    SettableFuture<String> future = SettableFuture.create();
    Throwable failure = new Throwable();
    future.setException(failure);
    assertThat(future.tryInternalFastPathGetFailure()).isEqualTo(failure);
  }

  public void testTrustedGetFailure_NotCompleted() {
    SettableFuture<String> future = SettableFuture.create();

    assertTrue(future.setException(new Exception("failure")));
    tester.testFailedFuture("failure");
  }

  public void testSetFailureNull() throws Exception {
    assertThrows(NullPointerException.class, () -> future.setException(null));
    assertFalse(future.isDone());
    assertTrue(future.setException(new Exception("failure")));
    tester.testFailedFuture("failure");
  }

  public void testCancel() throws Exception {