<connectionStrings configSource="connectionStrings.config" />

<?xml version="1.0" encoding="utf-8"?>
<connectionStrings>
  <add name="ConfigurationDatabase"
       connectionString="server=.;Integrated Security=true;database=test"/>
  <add name="TestDatabase"
       connectionString="server=TEST;Integrated Security=true;database=test"/>
</connectionStrings>