Set<ApiChange> acceptedApiChanges = (Set<ApiChange>) context.getUserData().get("acceptedApiChanges");
        Set<ApiChange> seenApiChanges = (Set<ApiChange>) context.getUserData().get("seenApiChanges");
        Set<ApiChange> left = new HashSet<>(acceptedApiChanges);
        left.removeAll(seenApiChanges);
        if (!left.isEmpty()) {
            String formattedLeft = CollectionUtils.join("\n", left);

    public void execute(ViolationCheckContext context) {
        Map<String, Object> userData = (Map<String, Object>) context.getUserData();
        userData.put("acceptedApiChanges", acceptedApiChanges);
        userData.put("seenApiChanges", new HashSet<ApiChange>());
    }

abstract class AbstractContextAwareRuleSpecification extends Specification {
    @TempDir
    File testDir

    ViolationCheckContext context = new ViolationCheckContext() {
        Map userData = [seenApiChanges: [] as Set]

        String getClassName() { return null }

        Map<String, ?> getUserData() { return userData }

        Object getUserData(String key) {
            return userData[key]
        }