xUnit1027 Error

Collection definition classes must be public

Cause

A collection definition class is not public.

xUnit.net will not discover the collection definition class if the class is not public.

To fix a violation of this rule, make the collection definition class public.

using Xunit;

[CollectionDefinition("CollectionName")]
class CollectionDefinitionClass
{ }

using Xunit;

[CollectionDefinition("CollectionName")]
public class CollectionDefinitionClass
{ }