Migrate PHPUnit configuration to version 9 (#735)

* Migrate PHPUnit configuration to version 9

* Addubg .editorconfig for phpunit.xml

Author: Nyholm

phpunit.xml.dist

@@ -1,26 +1,23 @@
 <?xml version="1.0" encoding="UTF-8"?>
-
 <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-         xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/5.2/phpunit.xsd"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd"
          backupGlobals="false"
          colors="true"
          bootstrap="vendor/autoload.php"
          failOnRisky="true"
          failOnWarning="true"
 >
-    <php>
-        <ini name="error_reporting" value="-1" />
-    </php>
-
-    <testsuites>
-        <testsuite name="Test Suite">
-            <directory>./tests/</directory>
-        </testsuite>
-    </testsuites>
-
-    <filter>
-        <whitelist>
-            <directory>./src</directory>
-        </whitelist>
-    </filter>
+  <coverage>
+    <include>
+      <directory>./src</directory>
+    </include>
+  </coverage>
+  <php>
+    <ini name="error_reporting" value="-1"/>
+  </php>
+  <testsuites>
+    <testsuite name="Test Suite">
+      <directory>./tests/</directory>
+    </testsuite>
+  </testsuites>
 </phpunit>