From 320ed259c45ab4cf7911f6a275e1a0beac678190 Mon Sep 17 00:00:00 2001
From: Takashi Matsuo <tmatsuo@google.com>
Date: Thu, 25 Jun 2020 10:01:55 -0700
Subject: [PATCH] add a section for installing coreutils on MacOS (#4167)

fixes #4166
---
 AUTHORING_GUIDE.md | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/AUTHORING_GUIDE.md b/AUTHORING_GUIDE.md
index 1ef11b860691..184d66031239 100644
--- a/AUTHORING_GUIDE.md
+++ b/AUTHORING_GUIDE.md
@@ -532,6 +532,13 @@ $ ../scripts/run_tests_local.sh . lint
 If your test needs a service account, you have to create a service
 account and download the JSON key to `testing/service-account.json`.
 
+On MacOS systems, you also need to install `coreutils` to use
+`scripts/run_tests_local.sh`. Here is how to install it with `brew`:
+
+```sh
+$ brew install coreutils
+```
+
 ### Google Cloud Storage Resources
 
 Certain samples require integration with Google Cloud Storage (GCS), most