add spec for Range#=== to behave like Range#cover? in Ruby 2.7

core/range/case_compare_spec.rb

@@ -25,4 +25,9 @@
       (range === RangeSpecs::WithoutSucc.new(2)).should == true
     end
   end
+
+  ruby_version_is "2.7" do
+    it_behaves_like :range_cover_and_include, :===
+    it_behaves_like :range_cover, :===
+  end
 end

core/range/cover_spec.rb

@@ -6,4 +6,5 @@
 describe "Range#cover?" do
   it_behaves_like :range_cover_and_include, :cover?
   it_behaves_like :range_cover, :cover?
+  it_behaves_like :range_cover_subrange, :cover?
 end

core/range/shared/cover.rb

@@ -90,7 +90,9 @@
       end
     end
   end
+end
 
+describe :range_cover_subrange, shared: true do
   ruby_version_is "2.6" do
     context "range argument" do
       it "accepts range argument" do