Use the shared examples in the preexisting tests

this also serves to test the cwm/rspec testing library and have it
contribute to testing coverage stats

library/cwm/test/abstract_widget_test.rb

@@ -3,8 +3,11 @@
 require_relative "test_helper"
 
 require "cwm/abstract_widget"
+require "cwm/rspec"
 
 describe CWM::AbstractWidget do
+  include_examples "CWM::AbstractWidget"
+
   describe "#widget_id" do
     class T1 < CWM::AbstractWidget
       def initialize(id: nil)

library/cwm/test/custom_widget_test.rb

@@ -1,27 +1,34 @@
 require_relative "test_helper"
 
 require "cwm/custom_widget"
+require "cwm/rspec"
 
 describe CWM::CustomWidget do
-  describe "#description" do
-    context "handle_all_events is false" do
-      class CustomTestWidget < CWM::CustomWidget
-        def initialize
-          self.handle_all_events = false
-          self.widget_id = "test_widget"
-        end
+  class CustomTestWidget < CWM::CustomWidget
+    def contents
+      HBox(
+        InputField(Id(:first), "test"),
+        PushButton(Id("second"), "Discover 42")
+      )
+    end
+  end
+  subject { CustomTestWidget.new }
 
-        def contents
-          HBox(
-            InputField(Id(:first), "test"),
-            PushButton(Id("second"), "Discover 42")
-          )
-        end
+  include_examples "CWM::CustomWidget"
+
+  context "handle_all_events is false" do
+    class IsolationistTestWidget < CustomTestWidget
+      def initialize
+        self.handle_all_events = false
+        self.widget_id = "test_widget"
       end
-      subject { CustomTestWidget.new }
+    end
+    describe "#cwm_definition" do
+      subject { IsolationistTestWidget.new }
 
       it "adds to description to handle only ids in contents and widget_id" do
-        expect(subject.cwm_definition["handle_events"]).to eq [:first, "second", "test_widget"]
+        expect(subject.cwm_definition["handle_events"])
+          .to eq [:first, "second", "test_widget"]
       end
     end
   end

library/cwm/test/widgets_test.rb

@@ -3,6 +3,7 @@
 require_relative "test_helper"
 
 require "cwm/widget"
+require "cwm/rspec"
 
 describe CWM::RadioButtons do
 
@@ -87,6 +88,8 @@ def cleanup
     end
   end
 
+  include_examples "CWM::CustomWidget"
+
   describe ".new" do
     it "has widget_id as passed" do
       subject = described_class.new(id: "test")