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

composer install --dev

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

vendor/bin/phpunit format_grid_courseformatlib_testcase course/format/grid/tests/courseformatlib_test.php
or
vendor\bin\phpunit format_grid_courseformatlib_testcase course/format/grid/tests/courseformatlib_test.php

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