minimum phpunit to start with

phpunit.xml

<?xml version="1.0" encoding="UTF-8"?>
<phpunit
    bootstrap="./tests/phpunit.bootstrap.php"
    processIsolation="false"
    verbose="true"
    strict="false"
    colors="true">
    <testsuites>
        <testsuite name="PHPUnit">
            <directory>./tests</directory>
        </testsuite>
    </testsuites>
    <filter>
        <whitelist>
            <directory suffix=".php">./src</directory>
        </whitelist>
    </filter>
    <logging>
        <log type="coverage-html" target="build/coverage"/>
    </logging>
</phpunit>