ShouldGetNuGetPackageFile() uses DefaultPackagePathResolver from NuGet.Core

TestContextExtensions.cs

/// <summary>
/// Test context extensions: should get nu get package file.
/// </summary>
/// <param name="context">The context.</param>
/// <param name="packageMeta">The package meta.</param>
/// <param name="sourceControlRoot">The source control root.</param>
/// <param name="searchPattern">The search pattern.</param>
public static string ShouldGetNuGetPackageFile(this TestContext context, IEnumerable<string> packageMeta, string sourceControlRoot, string searchPattern)
{
    Assert.IsNotNull(packageMeta, "The expected package metadata is not here.");
    context.ShouldFindFolder(sourceControlRoot);
    Assert.IsFalse(string.IsNullOrEmpty(searchPattern), "The expected package-file search pattern is not here.");

    var nugetRoot = Path.Combine(sourceControlRoot, "packages");
    context.ShouldFindFolder(nugetRoot);

    var meta = packageMeta.ToArray();
    Assert.AreEqual(2, meta.Length, "The expected number of package meta items are not here.");

    var resolver = new DefaultPackagePathResolver(nugetRoot);
    var packageDirectory = resolver.GetPackageDirectory(meta[0], new SemanticVersion(meta[1]));

    var searchRoot = Path.Combine(nugetRoot, packageDirectory);
    searchPattern = string.Format(searchPattern, meta[0]);
    var path = Directory.GetFiles(searchRoot, searchPattern, SearchOption.AllDirectories).FirstOrDefault();
    context.ShouldFindFile(path);

    return path;
}