I have written a discovery in my SCOM 2012 MP as below:

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<ManagementPackFragment SchemaVersion="2.0" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Monitoring>
    <Discoveries>
      <Discovery ID="TestDemo.TestDemo.Discovery.Test" Target="SNL!System.NetworkManagement.Node" Enabled="true" ConfirmDelivery="false" Remotable="true" Priority="Normal">
        <Category>Discovery</Category>
        <DiscoveryTypes>
          <DiscoveryClass TypeID="TestDemo.Class.Test">
            <Property TypeID="TestDemo.Class.Test" PropertyID="SerialNumber" />
            <Property TypeID="TestDemo.Class.Test" PropertyID="totalCapacity" />
          </DiscoveryClass>
        </DiscoveryTypes>
        <DataSource ID="DS" TypeID="TestDemo.DataSource.TestDiscovery">
          <IPAddress>$Target/Property[Type="SNL!System.NetworkManagement.Node"]/SNMPAddress$</IPAddress>
          <Version>$Target/Property[Type="SNL!System.NetworkManagement.Node"]/SNMPVersion$</Version>
          <CommunityString>$RunAs[Name="SNL!System.NetworkManagement.Snmp.MonitoringAccount"]/CommunityString$</CommunityString>
          <Interval>20</Interval>
        </DataSource>
      </Discovery>
    </Discoveries>
  </Monitoring>
  <LanguagePacks>
    <LanguagePack ID="ENU" IsDefault="true">
      <DisplayStrings>
        <DisplayString ElementID="TestDemo.TestDemo.Discovery.Test">
          <Name>Test Array Discovery</Name>
          <Description>Description for the Test Array</Description>
        </DisplayString>
      </DisplayStrings>
    </LanguagePack>
  </LanguagePacks>
</ManagementPackFragment>

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Note that the CommunityString is assigned in the way as below:

          <CommunityString>$RunAs[Name="SNL!System.NetworkManagement.Snmp.MonitoringAccount"]/CommunityString$</CommunityString>

Now, I run this discovery in Simulator, but there is no place to fill in my CommunityString.

So, I want to know how to give the value of $RunAs[Name="SNL!System.NetworkManagement.Snmp.MonitoringAccount"]/CommunityString$ in the simulator.

Thanks!