in TeamCity.ServiceMessages/Write/Special/Impl/Writer/TeamCityTestWriter.cs [21:26]
public void WriteStdOutput(string text)
{
if (text == null) throw new ArgumentNullException(nameof(text));
//##teamcity[testStdOut name='testname' out='text' tc:tags='tc:parseServiceMessagesInside']
PostMessage(new ServiceMessage("testStdOut") {{"name", _testName}, {"out", text}, {"tc:tags", "tc:parseServiceMessagesInside"}});
}