Is your feature request related to a problem?

The InThreadIMDServer serves an MDA Universe in pure Python for testing, but it has some test-specific methods like expect_header and has some placeholder data specifically for testing (like in the energy packet).

Describe the solution you'd like

A more generalized class could be made similar to InThreadIMDServer for the use case of serving a prewritten trajectory via IMD.

Describe alternatives you've considered

Don't do anything