code: public void setSeed(String randomSeed) {
      if (!Strings.isNullOrEmpty(getProject().getUserProperty(SYSPROP_RANDOM_SEED()))) {
        String userProperty = getProject().getUserProperty(SYSPROP_RANDOM_SEED());
        if (!userProperty.equals(randomSeed)) {
          log("Ignoring seed attribute because it is overridden by user properties.", Project.MSG_WARN);
        }
      } else if (!Strings.isNullOrEmpty(randomSeed)) {
        this.random = randomSeed;
      }
    }
docs: Initial random seed used for shuffling test suites and other sources
  of pseudo-randomness. If not set, any random value is set.
  
  <p>The seed's format is compatible with {@link RandomizedRunner} so that
  seed can be fixed for suites and methods alike.