void test_add() {
    TS_ASSERT_EQUALS(tbl->at(state, 0), cNil);
    TS_ASSERT_EQUALS(tbl->at(state, 1), cNil);

    tbl->store(state, Fixnum::from(1), Fixnum::from(2));

    TS_ASSERT_EQUALS(tbl->at(state, 0), Fixnum::from(1));
    TS_ASSERT_EQUALS(tbl->at(state, 1), Fixnum::from(2));
  }