Add tests for macOS check

Library/Homebrew/rubocops/lines_cop.rb

@@ -248,13 +248,13 @@ module RuboCop
             next unless method_called?(m, :new)
             problem "`depends_on` can take requirement classes instead of instances"
           end
-          #
-          # os = [:leopard?, :snow_leopard?, :lion?, :mountain_lion?]
-          # os.each do |version|
-          #   find_instance_method_call(body_node, :MacOS, version) do |m|
-          #     problem "\"#{m.source}\" is deprecated, use a comparison to MacOS.version instead"
-          #   end
-          # end
+
+          os = [:leopard?, :snow_leopard?, :lion?, :mountain_lion?]
+          os.each do |version|
+            find_instance_method_call(body_node, "MacOS", version) do |m|
+              problem "\"#{m.source}\" is deprecated, use a comparison to MacOS.version instead"
+            end
+          end
           #
           # dirPattern(body_node) do |m|
           #   next unless m =~ /\[("[^\*{},]+")\]/

Library/Homebrew/test/rubocops/lines_cop_spec.rb

@@ -527,6 +527,27 @@ describe RuboCop::Cop::FormulaAudit::Miscellaneous do
 
       inspect_source(cop, source)
 
+      expected_offenses.zip(cop.offenses).each do |expected, actual|
+        expect_offense(expected, actual)
+      end
+    end
+    it "with old style OS check" do
+      source = <<-EOS.undent
+        class Foo < Formula
+          desc "foo"
+          url 'http://example.com/foo-1.0.tgz'
+          depends_on :foo if MacOS.snow_leopard?
+        end
+      EOS
+
+      expected_offenses = [{  message: "\"MacOS.snow_leopard?\" is deprecated, use a comparison to MacOS.version instead",
+                              severity: :convention,
+                              line: 4,
+                              column: 21,
+                              source: source }]
+
+      inspect_source(cop, source)
+
       expected_offenses.zip(cop.offenses).each do |expected, actual|
         expect_offense(expected, actual)
       end