[feature] ability to run a single test through the command line

[ngarbezza]

Is your feature request related to a problem? Please describe. If we have many tests and we might want to focus just on one, we don't have a way to do that.

Describe the solution you'd like Pass a file name and a line number file_name:line_number as argument to a new command or use node tests.js and create a testy runner just for that test