Fixes related to multi-root support for tests

[DonJayamanne]

For #4268

• Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
• Title summarizes what is changing
• Has a news entry file (remember to thank yourself!)
• [n/a] Has sufficient logging.
• Has telemetry for enhancements.
• [n/a] Unit tests & system/integration tests are added/updated
• [n/a] Test plan is updated as appropriate
• [n/a] package-lock.json has been regenerated by running npm install (if dependencies have changed)
• [n/a] The wiki is updated with any design decisions/details.

[codecov]

Codecov Report

Merging #4667 into master will increase coverage by 1%.
The diff coverage is 67%.

@@          Coverage Diff           @@
##           master   #4667   +/-   ##
======================================
+ Coverage      77%     77%   +1%     
======================================
  Files         446     446           
  Lines       21218   21220    +2     
  Branches     3471    3472    +1     
======================================
+ Hits        16290   16294    +4     
+ Misses       4924    4922    -2     
  Partials        4       4

Flag	Coverage Δ
#Linux	66% <47%> (+1%)	⬆️
#Windows	66% <47%> (+1%)	⬆️
#macOS	66% <47%> (+1%)	⬆️

[ericsnowcurrently]

Mostly LGTM. I think there's one typo of a variable name.