It's not complete, but a few of the micro:bit examples work. It runs in your browser.
This is not the official Touch Develop simulator, which is described here, and is doubtless more capable in every way :-). In particular, that probably emulates the hardware, which is a much more reliable approach.
This is just a toy.
Create and activate a Python 3 virtualenv directory, then run:
pip install -U -r prereqs.txt
pip install -U -r requirements.txt
python3 -m bitlike examples/snake.py
It will print "Serving at http://localhost:8888/".
Follow the link, or copy it into your browser.
You can stop the simulator by holding down Ctrl and pressing 'c' (Ctrl-C).
You can keep the browser window open and reuse it if you run another simulation.