Conditions on packs do not work properly

when I tried to set condition for packs, it does not work, have any of you met the same problem? Below is the xml part.

<variables>
<variable name="do.test" value="0" />
</variables>
<conditions>
<condition type="variable" id="do_test">
<name>do.test</name>
<value>1</value>
</condition>
</conditions>
<packs>
<pack name="Database Configuration" required="no" condition="do_test">
<description>The database configuration</description>
</pack>
</packs>

When I run the install.jar with -DTRACE-true, I can see the condition do_test is set to false, but the pack is still visible.I tried to find some thing in the souce code, but did not find the place where the conditions of the packs are checked before showing it.