using (var folder = new TestFolder())
{
    // Create a package with files and dependencies
    var nupkg = TestNupkg.Create("MyPackage", "1.0.0");
    nupkg.AddFile("lib/net8.0/MyPackage.dll");
    nupkg.AddDependency("Newtonsoft.Json", "[13.0.0, )");

    // Save the .nupkg to disk
    var path = nupkg.Save(folder);

    // Use the generated package in your test
    using (var reader = new PackageArchiveReader(path.FullName))
    {
        var identity = reader.GetIdentity();
        // assert, verify, etc.
    }
}

var nuspec = new TestNuspec()
{
    Id = "MyPackage",
    Version = "2.0.0-beta.1",
    Authors = "TestAuthor",
    Description = "A test package",
    Tags = "test example"
};

var nupkg = nuspec.CreateNupkg();
nupkg.AddFile("lib/net8.0/MyPackage.dll", fileBytes);
nupkg.Save(outputDir);

var logger = new TestLogger();

// Pass logger to NuGet APIs...

// Inspect logged messages
var allMessages = logger.GetMessages();
var warnings = logger.GetMessages(LogLevel.Warning);