The Test Bindings button was disabled (greyed out) for any attribute bound
to a non-OPC-UA connection. BuildTestableRows() filtered to protocol ==
"OpcUa", a stale gate left over from when OPC UA was the only protocol.
ReadTagValuesCommand is protocol-agnostic (routes through
IDataConnection.ReadBatchAsync, which MxGatewayDataConnection implements),
so the filter only blocked the UI — mirroring the already-fixed IsBrowsable.
Remove the OPC-UA-only filter and update the stale comments. Add a bUnit
regression test (theory over MxGateway + OpcUa) asserting the button is
enabled for a readable-protocol binding.
Verified live: dialog opens for an MxGateway binding and returns a
Good-quality read.
Joseph Doherty
4881f9c23c