}

  private void expectReturnsTrue(Target target) {
    String message = Platform.format("retainAll(%s) should return true", target);
    assertTrue(message, collection.retainAll(target.toRetain));
  }

  private void expectReturnsFalse(Target target) {
    String message = Platform.format("retainAll(%s) should return false", target);
    assertFalse(message, collection.retainAll(target.toRetain));
  }

  private static class Sha512Holder {
    static final HashFunction SHA_512 =
        new MessageDigestHashFunction("SHA-512", "Hashing.sha512()");
  }

  /**
   * Returns a hash function implementing the Message Authentication Code (MAC) algorithm, using the
   * MD5 (128 hash bits) hash function and the given secret key.
   *
   * <p>If you are designing a new system that needs HMAC, prefer {@link #hmacSha256} or other

      return conflictingStackTrace;
    }

    /**
     * Appends the chain of messages from the {@code conflictingStackTrace} to the original {@code
     * message}.
     */
    @Override
    public String getMessage() {
      // requireNonNull is safe because ExampleStackTrace sets a non-null message.
      StringBuilder message = new StringBuilder(requireNonNull(super.getMessage()));

          }
        };

    private PermittedMetaException(String message) {
      super(message);
    }

    abstract boolean isPermitted(Exception exception);

    void assertPermitted(Exception exception) {
      if (!isPermitted(exception)) {
        String message =
            "Exception "
                + exception.getClass().getSimpleName()

        new RuntimeException("but culottes have a tendancy to ride up!");
    final Object subscriber =
        new Object() {
          @Subscribe
          public void throwExceptionOn(String message) {
            throw exception;
          }
        };
    eventBus.register(subscriber);
    eventBus.post(EVENT);

    assertEquals("Cause should be available.", exception, handler.exception);

        new RuntimeException("but culottes have a tendancy to ride up!");
    final Object subscriber =
        new Object() {
          @Subscribe
          public void throwExceptionOn(String message) {
            throw exception;
          }
        };
    eventBus.register(subscriber);
    eventBus.post(EVENT);

    assertEquals("Cause should be available.", exception, handler.exception);

  }

  private void expectReturnsTrue(Target target) {
    String message = Platform.format("retainAll(%s) should return true", target);
    assertTrue(message, collection.retainAll(target.toRetain));
  }

  private void expectReturnsFalse(Target target) {
    String message = Platform.format("retainAll(%s) should return false", target);
    assertFalse(message, collection.retainAll(target.toRetain));
  }

    } catch (AssertionFailedError t) {
      threadRecordFailure(t);
      throw t;
    }
  }

  /** Calls threadFail with message "should throw exception". */
  public void threadShouldThrow() {
    threadFail("should throw exception");
  }

  /** Calls threadFail with message "should throw" + exceptionName. */
  public void threadShouldThrow(String exceptionName) {
    threadFail("should throw " + exceptionName);
  }

     * even entire message) that simultaneously:
     *
     * - _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_)
     *

          }
        };

    private PermittedMetaException(String message) {
      super(message);
    }

    abstract boolean isPermitted(Exception exception);

    void assertPermitted(Exception exception) {
      if (!isPermitted(exception)) {
        String message =
            "Exception "
                + exception.getClass().getSimpleName()