[ticket/9990] Add docs for running slow tests

PHPBB3-9990

phpunit.xml.all

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<phpunit backupGlobals="true"
+         backupStaticAttributes="true"
+         colors="true"
+         convertErrorsToExceptions="true"
+         convertNoticesToExceptions="true"
+         convertWarningsToExceptions="true"
+         processIsolation="false"
+         stopOnFailure="false"
+         syntaxCheck="false"
+         bootstrap="tests/bootstrap.php"
+>
+    <testsuites>
+        <testsuite name="phpBB Test Suite">
+            <directory suffix="_test.php">./tests/</directory>
+        </testsuite>
+    </testsuites>
+
+    <filter>
+        <blacklist>
+            <directory>./tests/</directory>
+        </blacklist>
+    </filter>
+</phpunit>