Fix InterfacesTable test

test/lib/y2firewall/widgets/interfaces_table_test.rb

@@ -33,7 +33,7 @@
 
   let(:eth0) do
     instance_double(
-      Y2Firewall::Firewalld::Interface, name: "eth0", device_name: DEVICE_NAME, zone: "public"
+      Y2Firewall::Firewalld::Interface, name: "eth0", device_name: DEVICE_NAME, zone: public_zone
     )
   end
 
@@ -43,6 +43,18 @@
     )
   end
 
+  let(:public_zone) do
+    instance_double(
+      Y2Firewall::Firewalld::Zone, name: "public", interfaces: [], remove_interface: nil
+    )
+  end
+
+  let(:dmz_zone) do
+    instance_double(
+      Y2Firewall::Firewalld::Zone, name: "dmz", remove_interface: nil
+    )
+  end
+
   let(:interfaces) { [eth0, eth1] }
 
   let(:change_zone_button) do
@@ -51,6 +63,10 @@
 
   include_examples "CWM::Table"
 
+  before do
+    allow(public_zone).to receive(:interfaces).and_return([eth0])
+  end
+
   describe "#items" do
     it "returns the list of interfaces" do
       expect(widget.items).to eq(