Adding an XML configuration for phpunit.

tools/phpunit/phpunit.xml

+<?xml version="1.0" encoding="UTF-8"?>
+
+<phpunit backupGlobals="false"
+         backupStaticAttributes="false"
+         colors="true"
+         convertErrorsToExceptions="true"
+         convertNoticesToExceptions="true"
+         convertWarningsToExceptions="true"
+         processIsolation="false"
+         stopOnFailure="false"
+         syntaxCheck="false"
+         bootstrap="./../../vendor/autoload.php">
+    <testsuites>
+        <testsuite name="Test Suite">
+            <directory>./../../tests</directory>
+        </testsuite>
+    </testsuites>
+</phpunit>