in src/OpenTelemetryEngineTests/Traces/FunctionsActivityBuilderTests.cs [19:28]
public void StartInternalActivity_CreatesValidActivity()
{
string invocationId = Guid.NewGuid().ToString();
var startActivityResponse = FunctionsActivityBuilder.StartInternalActivity(invocationId, "", "");
Assert.NotNull(startActivityResponse);
Assert.NotNull(startActivityResponse.activity);
Assert.Equal(invocationId, startActivityResponse.activity.Tags.Where(x => x.Key == "invocationId").First().Value);
}