.

node_modules/@jest/core/build/testSchedulerHelper.js

@@ -0,0 +1,51 @@
+'use strict';
+
+Object.defineProperty(exports, '__esModule', {
+  value: true
+});
+exports.shouldRunInBand = shouldRunInBand;
+
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+const SLOW_TEST_TIME = 1000;
+
+function shouldRunInBand(
+  tests,
+  timings,
+  {detectOpenHandles, maxWorkers, watch, watchAll}
+) {
+  // detectOpenHandles makes no sense without runInBand, because it cannot detect leaks in workers
+  if (detectOpenHandles) {
+    return true;
+  }
+  /*
+   * Run in band if we only have one test or one worker available, unless we
+   * are using the watch mode, in which case the TTY has to be responsive and
+   * we cannot schedule anything in the main thread. Same logic applies to
+   * watchAll.
+   * Also, if we are confident from previous runs that the tests will finish
+   * quickly we also run in band to reduce the overhead of spawning workers.
+   * Finally, the user can provide the runInBand argument in the CLI to
+   * force running in band.
+   * https://github.com/facebook/jest/blob/700e0dadb85f5dc8ff5dac6c7e98956690049734/packages/jest-config/src/getMaxWorkers.js#L14-L17
+   */
+
+  const isWatchMode = watch || watchAll;
+  const areFastTests = timings.every(timing => timing < SLOW_TEST_TIME);
+  const oneWorkerOrLess = maxWorkers <= 1;
+  const oneTestOrLess = tests.length <= 1;
+
+  if (isWatchMode) {
+    return oneWorkerOrLess || (oneTestOrLess && areFastTests);
+  }
+
+  return (
+    oneWorkerOrLess ||
+    oneTestOrLess ||
+    (tests.length <= 20 && timings.length > 0 && areFastTests)
+  );
+}