code: @Override
      public void describeTo(Description description) {
          describeKeyTo(description);
          if (isRun) {
              if (hasResult()) {
                  description.appendText(" = ")
                             .appendValue(getResult());
              } else {
                  description.appendText("-> ")
                             .appendValue(getException());
              }
          }
      }
docs: {@inheritDoc}