Provide target framework as an envvar to tests. (#84)

Turkey/Program.cs

@@ -85,6 +85,7 @@ public static async Task<int> Run(string testRoot,
  Cleaner cleaner = new Cleaner();
 
  DotNet dotnet = new DotNet();
+ Version runtimeVersion = dotnet.LatestRuntimeVersion;
 
  TestOutput defaultOutput = new TestOutputFormats.NewOutput();
 
@@ -101,19 +102,21 @@ public static async Task<int> Run(string testRoot,
  var sanitizer = new EnvironmentVariableSanitizer();
  var envVars = sanitizer.SanitizeCurrentEnvironmentVariables();
 
- var traits = CreateTraits(dotnet.LatestRuntimeVersion, dotnet.LatestSdkVersion, platformIds, dotnet.IsMonoRuntime(dotnet.LatestRuntimeVersion), trait);
+ var traits = CreateTraits(runtimeVersion, dotnet.LatestSdkVersion, platformIds, dotnet.IsMonoRuntime(runtimeVersion), trait);
  Console.WriteLine($"Tests matching these traits will be skipped: {string.Join(", ", traits.OrderBy(s => s))}.");
 
+ envVars["TestTargetFramework"] = $"net{runtimeVersion.Major}.{runtimeVersion.Minor}";
+
  SystemUnderTest system = new SystemUnderTest(
  dotnet,
- runtimeVersion: dotnet.LatestRuntimeVersion,
+ runtimeVersion: runtimeVersion,
  sdkVersion: dotnet.LatestSdkVersion,
  platformIds: platformIds,
  environmentVariables: envVars,
  traits: traits
  );
 
- Version packageVersion = dotnet.LatestRuntimeVersion;
+ Version packageVersion = runtimeVersion;
  string nuGetConfig = await GenerateNuGetConfigIfNeededAsync(additionalFeed, packageVersion,
  useSourceBuildNuGetConfig: false);
  if (verbose && nuGetConfig != null)