PHPUnit Package
PHP Tools come with a bundled version of PHPUnit in case there isn't a user installation of PHPUnit in the project.
Custom PHPUnit
PHP Tools will use a particular PHPUnit version when it's configured in the composer.json
. Check Composer section, and ensure there is phpunit/phpunit
composer package installed.
Bundled PHPUnit
In case there is no phpunit/phpunit
composer package, the Test Explorer will use bundled PHPUnit; a stable version of PHPUnit chosen accordingly for the PHP version configured in the Project Properties.