{
  "methodDisplay": "method",
  "methodDisplayOptions": "replaceUnderscoreWithSpace",
  "parallelizeTestCollections": false
}

{
  "maxParallelThreads": 1,
  "methodDisplay": "method",
  "methodDisplayOptions": "replaceUnderscoreWithSpace",
  "parallelizeTestCollections": false
}

Set maximum xunit threads to 1
Set maximum xunit threads to 1

Only allow a maximum of 1 xunit parallel thread as suggested here: https://help.appveyor.com/discussions/problems/16354-nullreferenceexception-thrown-by-test-logger-during-build
