code: @Test public void assertRegisterTypeAdapter(){
    Gson beforeRegisterGson=GsonFactory.getGson();
    GsonFactory.registerTypeAdapter(GsonFactoryTest.class,new TypeAdapter(){
      @Override public Object read(    final JsonReader in) throws IOException {
        return null;
      }
      @Override public void write(    final JsonWriter out,    final Object value) throws IOException {
        out.jsonValue("test");
      }
    }
  );
    assertThat(beforeRegisterGson.toJson(new GsonFactoryTest()),is("{}"));
    assertThat(GsonFactory.getGson().toJson(new GsonFactoryTest()),is("test"));
  }
  