Fixed ReactFresh test/mock

packages/react-reconciler/src/__mocks__/scheduler/tracing.js

@@ -0,0 +1,11 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+// This placeholder is to support a legacy/regression test in ReactFresh-test.
+// Without this mock, jest.mock('scheduler/tracing') throws.

packages/react-refresh/package.json

@@ -28,6 +28,7 @@
   },
   "devDependencies": {
     "react-16-8": "npm:react@16.8.0",
-    "react-dom-16-8": "npm:react-dom@16.8.0"
+    "react-dom-16-8": "npm:react-dom@16.8.0",
+    "scheduler-0-13": "npm:scheduler@0.13.0"
   }
 }

packages/react-refresh/src/__tests__/ReactFresh-test.js

@@ -3844,6 +3844,10 @@ describe('ReactFresh', () => {
 
       // Redirect all React/ReactDOM requires to v16.8.0
       // This version predates Fast Refresh support.
+      jest.mock('scheduler', () => jest.requireActual('scheduler-0-13'));
+      jest.mock('scheduler/tracing', () =>
+        jest.requireActual('scheduler-0-13/tracing'),
+      );
       jest.mock('react', () => jest.requireActual('react-16-8'));
       jest.mock('react-dom', () => jest.requireActual('react-dom-16-8'));
 

yarn.lock

@@ -12319,6 +12319,14 @@ saxes@^5.0.0:
   dependencies:
     xmlchars "^2.2.0"
 
+"scheduler-0-13@npm:scheduler@0.13.0":
+  version "0.13.0"
+  resolved "https://registry.yarnpkg.com/scheduler/-/scheduler-0.13.0.tgz#e701f62e1b3e78d2bbb264046d4e7260f12184dd"
+  integrity sha512-w7aJnV30jc7OsiZQNPVmBc+HooZuvQZIZIShKutC3tnMFMkcwVN9CZRRSSNw03OnSCKmEkK8usmwcw6dqBaLzw==
+  dependencies:
+    loose-envify "^1.1.0"
+    object-assign "^4.1.1"
+
 scheduler@^0.11.0:
   version "0.11.3"
   resolved "https://registry.yarnpkg.com/scheduler/-/scheduler-0.11.3.tgz#b5769b90cf8b1464f3f3cfcafe8e3cd7555a2d6b"