I had similar problem and found different solution.
I have install phpunit with composer globaly
composer global require phpunit/phpunit "^9"
and localy in my project (both same version "^9").
cd C:/fullpath/to/myproject
composer require-dev phpunit/phpunit "^9"
However for some reason phpunit was triggered from the xampp folder.. so what I did was removed
phpunit
phpunit.bat
From C:\xampp\php and it worked for me.
Just remember to set composer path to your env path in Windows.
Now you can create phpunit.xml in you project root (here is what worked for me):
<?xml version="1.0" encoding="UTF-8"?>
<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.0/phpunit.xsd"
bootstrap="vendor/autoload.php"
colors="true"
testdox="true"
verbose="false"
convertErrorsToExceptions="true"
convertNoticesToExceptions="true"
convertWarningsToExceptions="true"
forceCoversAnnotation="true"
processIsolation="false"
stopOnError="false"
stopOnFailure="false"
stopOnIncomplete="false"
stopOnSkipped="false"
stopOnRisky="false">
<testsuites>
<testsuite name="default">
<directory suffix="Test.php">tests</directory>
</testsuite>
</testsuites>
<filter>
<whitelist processUncoveredFilesFromWhitelist="true">
<directory suffix=".php">src</directory>
</whitelist>
</filter>
</phpunit>
Then just cd to my root and run phpunit in my terminal to run all my tests from the tests folder
Hope you will find this information helpfull
*Editor: Hypper.js - using Git Bash on Windows 10 (incase you wonder)