code: private ComparisonState compareAttributes(Attr control,
                                                XPathContext controlContext,
                                                Attr test,
                                                XPathContext testContext) {
          return compareAttributeExplicitness(control, controlContext, test,
                                              testContext).apply()
              .andThen(new Comparison(ComparisonType.ATTR_VALUE,
                                      control, getXPath(controlContext),
                                      control.getValue(), getParentXPath(controlContext),
                                      test, getXPath(testContext),
                                      test.getValue(), getParentXPath(testContext)));
      }
docs: Compares properties of an attribute.