The non-test method is public.
A fixture should not contain any public non-test methods.
A fixture should be self-contained and not have methods callable by other classes.
How to fix violations
If the methods are purely for this class, mark them as 'private'. If the methods are used by other classes move these methods to a separate class used by the relevant test fixtures.
Via ruleset file
Configure the severity per project, for more info see MSDN.
Via .editorconfig file
# NUnit1028: The non-test method is public. dotnet_diagnostic.NUnit1028.severity = chosenSeverity
chosenSeverity can be one of
Via #pragma directive
#pragma warning disable NUnit1028 // The non-test method is public. Code violating the rule here #pragma warning restore NUnit1028 // The non-test method is public.
Or put this at the top of the file to disable all instances.
#pragma warning disable NUnit1028 // The non-test method is public.
[System.Diagnostics.CodeAnalysis.SuppressMessage("Structure", "NUnit1028:The non-test method is public.", Justification = "Reason...")]