wait-for.ts

const sleep = async (timeout: number = 1000) =>
  // tslint:disable-next-line:no-string-based-set-timeout
  new Promise((res) => setTimeout(res, timeout));

/**
 * A test-only utility that executes a function until a given condition is met.
 * Useful to wait for asynchronous operations to complete on integration tests.
 * If the condition is never met (`condition` never returns `true`) then tests will eventually timeout accordin to
 * the test framework timeout settings.
 * @param task Asynchronous function that will be repeatedly executed until the the desired `condition` is met.
 * @param condition Function that evalutes the results of `task`. Return `true` to indicate that the condition is met.
 * @param retryInterval Interval in milliseconds to wait between the next execution of `task`. Defaults to 100ms.
 * @return A promise that resolves with the last results returned by `task` when the condition is met.
 */
export const waitFor = async <T>(
  task: () => Promise<T>,
  condition: (taskResults: T) => boolean,
  retryInterval: number = 100,
): Promise<T> => {
  const results = await task();
  const isReady = condition(results);

  if (isReady) {
    return results;
  }

  await sleep(retryInterval);

  return waitFor(task, condition);
};