Migrate testing projects to xUnit.net v3

[raman-m]

Unit testing

The Ocelot.UnitTests project currently references the xunit package, which is actually xUnit Core Framework v2 using an outdated project template. Ocelot's unit testing project was created 9 years ago when only xUnit v2 existed, while xUnit Core Framework v3 was later introduced specifically for .NET 8+ projects with the 1st release 1.0.0 on December 16, 2024.

Motivation for New Feature

The xUnit.net v3 has the recommended project xunit.v3.templates for .NET 8+ projects. Plus, xUnit v3 offers some handy new features contributed by the community.

Acceptance testing

Migrating the Ocelot.AcceptanceTests project is possible due to its reference to the xUnit package. This would just be a temporary xUnit+BDDfy solution until transitioning from BDDfy package, which has not been maintained by the author since 2016, to an industry-standard library like SpecFlow (deprecated), Reqnroll, or others. Since BDD frameworks rely on standard test execution frameworks like MSTest, NUnit, or xUnit, moving the Ocelot.AcceptanceTests project to xUnit.net v3 package could also be a great option.

Note❗

• The BDDfy package has not been maintained since 2016, and the latest 8.0.* beta releases appear unprofessional. It should be removed from Ocelot's acceptance testing project once the migration to xUnit v3 is completed.
• The SpecFlow package is deprecated, and its code along with its repository was deleted from GitHub on December 31, 2024, due to its EOL status.