I can set the values of 'Reason' dropdown field for any 'State' change by modifying the Bug.xml (\Currituck\TypeDefinitions\bug.xml) <Transition> block
<TRANSITION from="Resolved" to="Closed">
<REASONS>
<DEFAULTREASON value="Resolution Confirmed"/>
<REASON value="Fixed"/>
<REASON value="Deferred"/>
<REASON value="Duplicate"/>
<REASON value="As Designed"/>
<REASON value="Unable to Reproduce"/>
<REASON value="Obsolete"/>
<REASON value="Test Passed"/>
</REASONS>
<FIELDS>
<FIELD refname="Microsoft.VSTS.Common.ClosedDate"><COPY from="clock"/></FIELD>
<FIELD refname="Microsoft.VSTS.Common.ClosedBy"><COPY from="currentuser"/></FIELD>
</FIELDS>
</TRANSITION>

Now, my question is: How can I make it user dependent ?
For example, If current user is in developer group (or, any specific user) he will see only two 'Reason' - 'Fixed' or, 'Duplicate'. So he can set either 'Fixed' or, 'Duplicate' but he cannot set 'Test Passed'. But if current user is project manager, he can set any reason.