You need to install Bats before running tests. You need to have Drupal 7 sample project installed in your projects directory. You must have next structure of projects directory:

projects
  ...
  \_ docksal
  \_ drupal7
  ...

You need to install additional bats sub-modules. To perform this, perform next actions.

cd ~/projects/docksal/tests
git submodule init
git submodule update

You can run any test from drupal7 directory using next command:

bats ../docksal/tests/start.bats

By default OS is "OS X" (mac). You can set enviroment for test (OS is mac|linux|win):

OS=linux bats ../docksal/tests/start.bats

You can run all tests using next command (it must be run from docksal/tests directory):

./run-tests.sh

Or you can set OS:

OS=linux ./run-tests.sh

or specify parameter:

./run-tests.sh linux

In most cases test name is same as commands name:

init.bats => fin init
start.bats => fin start
...

There are also files with tests for fin functions:

helper_functions.bats - Helper functions
basics_check_functions.bats - Basics check functions
control_functions.bats - Control functions

Tests directory contains troubleshooting.bats, which should not be started in general and not included in run-tests.sh. This test have to be performed when something goes wrong.