*/
@GwtCompatible
public final class TesterRequirements {
  private final Set<Feature<?>> presentFeatures;
  private final Set<Feature<?>> absentFeatures;

  public TesterRequirements(Set<Feature<?>> presentFeatures, Set<Feature<?>> absentFeatures) {
    this.presentFeatures = copyToSet(presentFeatures);
    this.absentFeatures = copyToSet(absentFeatures);
  }

  public TesterRequirements(TesterRequirements tr) {