TestAssignActivity2 is failing

Could not get TestAssignActivity working so I split into unit tests TestAssignActivity1 and TestAssignActivity2. It appears TestAssignActivity2 is failing due to the following syntax:

<copy>
<from variable="myVar" part="TestPart"/>
<to>$otherMsgVar.TestPart</to>
</copy>

while TestAssignActivity1 passes with replaced syntax:

<copy>
<from variable="myVar" part="TestPart"/>
<to variable="otherMsgVar" part="TestPart"/>
</copy>