Marionette's Python testrunner is used to run two different kinds of tests:
- The JavaScript WebAPI tests (FirefoxOS only)
- Marionette's own unit tests (all platforms)
The command-line to run these is generally the same; see Running Tests and the Marionette Test Runner for more details.
You can also write and run ad-hoc scripts that do not require the Marionette Test Runner; see Marionette for Interactive Python.
Gaia UI tests are also written in Python, but must be executed using the gaiatest runner, rather than using the Marionette testrunner directly.