Ref: https://docs.moodle.org/dev/PHPUnit

composer install --dev

php admin/tool/phpunit/cli/init.php

vendor/bin/phpunit theme_adaptable_toolbox_testcase theme/adaptable/tests/adaptabletoolbox_test.php
or
vendor\bin\phpunit theme_adaptable_toolbox_testcase theme/adaptable/tests/adaptabletoolbox_test.php

vendor/bin/phpunit --group theme_adaptable
or
vendor\bin\phpunit --group theme_adaptable