@Override
    public String toString() {
      return "Invocations{" + "counter=" + counter + ", beforeInvocation=" + beforeInvocation
          + ", testInvocation=" + testInvocation + ", afterInvocation=" + afterInvocation + '}';
    }
Structure of rule callback and test invocations
geode-junit/src/test/java/org/apache/geode/test/junit/rules/RuleListTest.java