When you are running a specific PHP version in production, you need to generate a "composer.lock" locally based on that.
To instruct Composer which PHP version you use in Production servers. You can run the following command.
composer config platform.php 7.2
Which will add a similar values to your
Post inspired by this tweet by @nunomaduro
Sometimes you will find the need to ignore these platforms requirements, which can be done like this:
composer update phpunit/phpunit --ignore-platform-reqs