Add #content_with_named_vars spec

Author: rastating

spec/core/data_file_spec.rb

@@ -14,4 +14,12 @@
       expect(subject.php_content).to_not match(/^<\?php.*\?>^/)
     end
   end
+
+  describe '#content_with_named_vars' do
+    it 'returns the file contents with the specified string replacements' do
+      allow(subject).to receive(:content).and_return('var $name = "$value";')
+      content = subject.content_with_named_vars('$name' => 'foo', '$value' => 'bar')
+      expect(content).to eq('var foo = "bar";')
+    end
+  end
 end