Function runContinuous

e2e/runJest.ts:190–282

(
  dir: string,
  args?: Array<string>,
  options: RunJestOptions = {},
)

// Runs `jest` continuously (watch mode) and allows the caller to wait for
// conditions on stdout and stderr and to end the process.
export const runContinuous = function (
  dir: string,
  args?: Array<string>,
  options: RunJestOptions = {},
) {
  const jestPromise = spawnJest(dir, args, {timeout: 30_000, ...options}, true);

  let stderr = '';
  let stdout = '';
  const pending = new Set<CheckerFunction>();
  const pendingRejection = new WeakMap<CheckerFunction, () => void>();

  jestPromise.addListener('exit', () => {
    for (const fn of pending) {
      const reject = pendingRejection.get(fn);

      if (reject) {
        console.log('stdout', normalizeStreamString(stdout, options));
        console.log('stderr', normalizeStreamString(stderr, options));

        reject();
      }
    }
  });

  const dispatch = () => {
    for (const fn of pending) {
      fn({stderr, stdout});
    }
  };

  jestPromise.stdout!.pipe(
    new Writable({
      write(chunk, _encoding, callback) {
        stdout += chunk.toString('utf8');
        dispatch();
        callback();
      },
    }),
  );

  jestPromise.stderr!.pipe(
    new Writable({
      write(chunk, _encoding, callback) {
        stderr += chunk.toString('utf8');
        dispatch();
        callback();
      },
    }),
  );

  const continuousRun = {
    async end() {
      jestPromise.kill();

      const result = await jestPromise;

      // Not sure why we have to assign here... The ones on `result` are empty strings