this.groupId = (groupId != null && !groupId.isEmpty()) ? groupId : null;
        this.artifactId = (artifactId != null && !artifactId.isEmpty()) ? artifactId : null;
        this.classifier = (classifier != null && !classifier.isEmpty()) ? classifier : null;
        this.extension = (extension != null && !extension.isEmpty()) ? extension : null;
        this.version = (version != null && !version.isEmpty()) ? version : null;

			default:
				return errUnknownXMLTag
			}
		}
	}
	return nil
}

// IsEmpty returns true if Filter is not specified in the XML
func (f Filter) IsEmpty() bool {
	return !f.set
}

// Validate - validates the filter element
func (f Filter) Validate() error {
	if f.IsEmpty() {
		return errXMLNotWellFormed
	}
	// A Filter must have exactly one of Prefix, Tag,

    assertThat(requirements.getPresentFeatures()).isEmpty();
    assertThat(requirements.getAbsentFeatures()).isEmpty();
  }

  public void testBuildTesterRequirements_class_empty() throws Exception {
    @Require
    class Tester {}

    TesterRequirements requirements = buildTesterRequirements(Tester.class);

    assertThat(requirements.getPresentFeatures()).isEmpty();

    }

    public ExecutionListener chainListener(ExecutionListener listener) {
        if (eventSpies.isEmpty()) {
            return listener;
        }
        return new EventSpyExecutionListener(this, listener);
    }

    public RepositoryListener chainListener(RepositoryListener listener) {
        if (eventSpies.isEmpty()) {
            return listener;
        }
        return new EventSpyRepositoryListener(this, listener);

        Set<Artifact> resolved = new LinkedHashSet<>();

        if (projects == null || projects.isEmpty()) {
            return resolved;
        }

        if ((scopesToCollect == null || scopesToCollect.isEmpty())
                && (scopesToResolve == null || scopesToResolve.isEmpty())) {
            return resolved;
        }

        /*

        Logic for transitive global exclusions

    public boolean isEmpty() {
        return entry == null || vertices == null || vertices.isEmpty();
    }

    // ------------------------------------------------------------------------
    public boolean isEmptyEdges() {
        return isEmpty() || incidentEdges == null || incidentEdges.isEmpty();
    }

    for (Range<Integer> range1 : RANGES) {
      for (Range<Integer> range2 : RANGES) {
        boolean expectRejection =
            range1.isConnected(range2) && !range1.intersection(range2).isEmpty();
        ImmutableRangeMap.Builder<Integer, Integer> builder = ImmutableRangeMap.builder();
        builder.put(range1, 1).put(range2, 2);
        try {
          ImmutableRangeMap<Integer, Integer> unused = builder.build();

        buffer.append((groupId != null && !groupId.isEmpty()) ? groupId : "[unknown-group-id]");
        buffer.append(':');
        buffer.append((artifactId != null && !artifactId.isEmpty()) ? artifactId : "[unknown-artifact-id]");
        buffer.append(':');
        buffer.append((version != null && !version.isEmpty()) ? version : "[unknown-version]");

        return buffer.toString();
    }

        }
        if (!fields.isEmpty()) {
            queryBuilder.must(QueryBuilders.termsQuery(FieldNames.FIELDS, fields));
        }
        if (!languages.isEmpty()) {
            queryBuilder.must(QueryBuilders.termsQuery(FieldNames.LANGUAGES, languages));
        }
        if (!excludeWords.isEmpty()) {
            queryBuilder.mustNot(QueryBuilders.termsQuery(FieldNames.TEXT, excludeWords));

            boolean isGroupRecodeStarted = false;
            while ((line = reader.readLine()) != null) {
                line = stripComment(line).trim();
                if (StringUtil.isEmpty(line)) {
                    continue;
                }

                String value = getValue(USER_AGENT_RECORD, line);
                if (value != null) {
                    if (isGroupRecodeStarted) {