InternalTrace provides facilities for tracing the execution of the NUnit framework. Tests and classes under test may make use of Console writes, System.Diagnostics.Trace or various loggers and NUnit itself traps and processes each of them. For that reason, a separate internal trace is needed. Note: InternalTrace uses a global lock to allow multiple threads to write trace messages. This can easily make it a bottleneck so it must be used sparingly. Keep the trace Level as low as possible and only insert InternalTrace writes where they are needed. TODO: add some buffering and a separate writer thread as an option. TODO: figure out a way to turn on trace in specific classes only.