Open New Pane and Run Process

In the great advanced workflow video, Chris notes that it is helpful to bind a key to open panes and processes simultaneously as such:
bind-key p split-window -h "python3"
In my case, it would be very useful to have a key that runs the test file in the current directory and opens a new pane. I was wondering how this would be possible. All the test files will end in _test.sh or _test.py and I am using bats to test my shell scripts and unittest to test my python scripts. I tried:

bind-key C-b split-window -h "bats ./*_test.sh"
bind-key C-u split-window -h "unittest ./*_test.py"

I’m hoping someone has some advice as to how to do this.