Requires .Net 5.
All tests are unit tests. You can run the tests with your preferred test runner, or using the standard command line:
dotnet test
Regarding the test "WeekdaysAndBusinessDayTests.GivenHolidayList_BusinessDayCalculation_ShouldNotIncludeHolidays()". InlineData was preferred over MemberData here as the dates and holiday list are more readable.