void test_get_set(client &c) {
    c.flushdb();
    c.set("k1", "v1");
    assert(*c.get("k1")=="v1");
    c.set("k1", "v2");
    assert(*c.get("k1")=="v2");
    assert(!c.get("nonexist"));

    c.set("mykey", "10.5");
    c.incrbyfloat("mykey", "0.1");
    assert(*(c.get("mykey"))=="10.6");
}