Updated `Microsoft.NET.Test.Sdk` to version 17.11.1 and `xunit` to version 2.9.3. Updated `xunit.runner.visualstudio` to version 2.8.2 with additional metadata for asset inclusion and private asset behavior.
Added new dependencies: `FluentAssertions` (7.0.0) and `Moq` (4.20.72).
Introduced project references to `DocumentOperator.Domain`, `DocumentOperator.Application`, and `DocumentOperator.Infrastructure` to the test project.
No changes were made to the `coverlet.collector` dependency or the `<Using Include="Xunit" />` directive.
Added a new test project, `DocumentOperator.Tests`, to the solution targeting .NET 8.0. Configured the project as a non-packable test project with support for nullable reference types and implicit usings. Included dependencies for `xunit`, `Microsoft.NET.Test.Sdk`, and `coverlet.collector` for testing and code coverage.
Added a placeholder test class, `UnitTest1`, with a single test method, `Test1`, marked with the `[Fact]` attribute.
