public void addPoint(Point p) {
    mPoints.add(p);
  }
@Test
  public void json() throws Exception {
    IOTaskResult result = new IOTaskResult();
    result.addPoint(new IOTaskResult.Point(IOTaskResult.IOMode.READ, 100L, 20));
    result.addPoint(new IOTaskResult.Point(IOTaskResult.IOMode.WRITE, 100L, 5));
    ObjectMapper mapper = new ObjectMapper();
    String json = mapper.writeValueAsString(result);
    IOTaskResult other = mapper.readValue(json, IOTaskResult.class);
    checkEquality(result, other);
  }