Nesse caso, você poderia querer documentar como essa API externa *deveria* ser. Que *operação de rota* ela deveria ter, que corpo ela deveria esperar, que resposta ela deveria retornar, etc.

## Um aplicativo com callbacks { #an-app-with-callbacks }

Vamos ver tudo isso com um exemplo.

Imagine que você desenvolve um aplicativo que permite criar faturas.

    // then we know it must have given a pending toString value earlier. If not, then the future
    // completed after the timeout expired, and the message might be success.
    if (isDone()) {
      throw new TimeoutException(message + " but future completed as timeout expired");
    }
    throw new TimeoutException(message + " for " + futureToString);
  }

  @ParametricNullness

  /** The HTTP {@code ETag} header field name. */
  public static final String ETAG = "ETag";

  /** The HTTP {@code Expires} header field name. */
  public static final String EXPIRES = "Expires";

  /** The HTTP {@code Last-Modified} header field name. */
  public static final String LAST_MODIFIED = "Last-Modified";

  /** The HTTP {@code Link} header field name. */

                ErrorCategory.AUTHENTICATION, false), INVALID_CREDENTIALS("Invalid credentials", ErrorCategory.AUTHENTICATION,
                        false), SESSION_EXPIRED("Session expired", ErrorCategory.AUTHENTICATION, true),

        // File system errors
        FILE_NOT_FOUND("File not found", ErrorCategory.FILE_SYSTEM, false), PATH_NOT_FOUND("Path not found", ErrorCategory.FILE_SYSTEM,

                    if (time > maxAge || time < 0) {
                        if (logger.isDebugEnabled()) {
                            logger.debug("role info is expired: {} > {}", time, maxAge);
                        }
                        return;
                    }
                } catch (final NumberFormatException e) {

	ArgsList []*Expression `parser:"\"(\" (@@ (\",\" @@)*)?\")\""`
}

// CountFunc represents the COUNT sql function
type CountFunc struct {
	StarArg bool        `parser:" \"COUNT\" \"(\" ( @\"*\"?"`
	ExprArg *Expression `parser:" @@? )! \")\""`
}

// CastFunc represents CAST sql function
type CastFunc struct {
	Expr     *Expression `parser:" \"CAST\" \"(\" @@ "`

        .build()
    val urlWithIpAddress = urlWithIpAddress(server, "/path/foo")
    server.enqueue(
      MockResponse
        .Builder()
        .addHeader(
          "Set-Cookie: a=android; " +
            "expires=Fri, 31-Dec-9999 23:59:59 GMT; " +
            "path=/path; " +
            "domain=${urlWithIpAddress.host}; " +
            "secure",
        ).build(),
    )
    get(urlWithIpAddress)

    // then we know it must have given a pending toString value earlier. If not, then the future
    // completed after the timeout expired, and the message might be success.
    if (isDone()) {
      throw new TimeoutException(message + " but future completed as timeout expired");
    }
    throw new TimeoutException(message + " for " + futureToString);
  }

  @ParametricNullness

    // it still should only have executed once due to memoization
    assertEquals(1, countingSupplier.calls);

    Thread.sleep(150);

    assertEquals(20, (int) memoizedSupplier.get());
    // old value expired
    assertEquals(2, countingSupplier.calls);

    assertEquals(20, (int) memoizedSupplier.get());
    // it still should only have executed twice due to memoization
    assertEquals(2, countingSupplier.calls);
  }

    // it still should only have executed once due to memoization
    assertEquals(1, countingSupplier.calls);

    Thread.sleep(150);

    assertEquals(20, (int) memoizedSupplier.get());
    // old value expired
    assertEquals(2, countingSupplier.calls);

    assertEquals(20, (int) memoizedSupplier.get());
    // it still should only have executed twice due to memoization
    assertEquals(2, countingSupplier.calls);
  }