Can't specify test target OSX 10.13 High Sierra with Capabilities "platform": "MAC" when OSX 10.12 also exists as a Selenium Grid node

[aengwall]

Environment

• OS:
  • OSX 10.12 (Sierra) and 10.13 (High Sierra)
• Selenium Version:
  • Selenium server standalone 3.11.0
• Browser/Version:
  • Any

Expected Behavior

When running automated test with capabilities "platform": "MAC" it should run test only on OSX 10.13 High Sierra nodes. I can isolate tests targeting OSX 10.12 Sierra by using "platform": "SIERRA".
Currently no support for specifying nodes running High Sierra 10.13 OSX on selenium grid with existing Sierra 10.12 OSX nodes.

Actual Behavior -

Some tests run on 10.12 and some on 10.13.
Selenium hub routes tests to OSX 10.12 or 10.13 based on some routing pattern (round-robin,sequential,etc.)

Steps to reproduce -

Create a selenium grid with OSX 10.12 and 10.13.
Run tests with capabilities "platform": "MAC".

Refernce

Known and Supported Platforms that WebDriver runs on

https://github.com/SeleniumHQ/selenium/blob/master/java/client/src/org/openqa/selenium/Platform.java
Doesn't include identifier for MacOSX 10.13 High Sierra