Add tests for MACOS version consts usage

Library/Homebrew/rubocops/extend/formula_cop.rb

@@ -173,8 +173,8 @@ module RuboCop
       # if block given, yield matching nodes
       def find_const(node, const_name)
         return if node.nil?
-        node.each_child_node(:const) do |const_node|
-          next if const_node.const_name != const_name
+        node.each_descendant(:const) do |const_node|
+          next unless const_node.const_name == const_name
           @offensive_node = const_node
           @offense_source_range = const_node.source_range
           yield const_node if block_given?

Library/Homebrew/rubocops/lines_cop.rb

@@ -173,14 +173,14 @@ module RuboCop
             problem "Use \"if build.#{match[1].downcase}?\" instead"
           end
 
-          # find_const(body_node, :MACOS_VERSION) do
-          #   problem "Use MacOS.version instead of MACOS_VERSION"
-          # end
-          #
-          # find_const(body_node, :MACOS_FULL_VERSION) do
-          #   problem "Use MacOS.full_version instead of MACOS_FULL_VERSION"
-          # end
-          #
+          find_const(body_node, "MACOS_VERSION") do
+            problem "Use MacOS.version instead of MACOS_VERSION"
+          end
+
+          find_const(body_node, "MACOS_FULL_VERSION") do
+            problem "Use MacOS.full_version instead of MACOS_FULL_VERSION"
+          end
+
           # dependency(body_node) do |m|
           #   # handle symbols and shit: WIP
           #   next unless modifier?(m.parent)

Library/Homebrew/test/rubocops/lines_cop_spec.rb

@@ -1189,6 +1189,30 @@ describe RuboCop::Cop::FormulaAudit::Miscellaneous do
       end
     end
 
+    it "with MACOS_VERSION const" do
+      source = <<-EOS.undent
+        class Foo < Formula
+          desc "foo"
+          url 'http://example.com/foo-1.0.tgz'
+          test do
+            version = MACOS_VERSION
+          end
+        end
+      EOS
+
+      expected_offenses = [{  message: "Use MacOS.version instead of MACOS_VERSION",
+                              severity: :convention,
+                              line: 5,
+                              column: 14,
+                              source: source }]
+
+      inspect_source(cop, source)
+
+      expected_offenses.zip(cop.offenses).each do |expected, actual|
+        expect_offense(expected, actual)
+      end
+    end
+
   end
   def expect_offense(expected, actual)
     expect(actual.message).to eq(expected[:message])