class Handler {
    private final Map<String, String> map;

    public void handle(RequestResponse rr) {
        if (rr.isPut()) {
            map.put(rr.key(), rr.value());
            rr.response("OK");
        } else {
            rr.response(map.get(rr.key());
        }
    }
}

when(rr.isPut()).thenReturn(true);
when(rr.key()).thenReturn("key");
when(rr.value()).thenReturn("value");
handler.handle(rr);
verify(rr).response("OK");

reset(rr);

when(rr.isPut()).thenReturn(false);
when(rr.key()).thenReturn("key");
handler.handle(rr);
verify(rr).response("value");

reset(rr);

when(rr.isPut()).thenReturn(false);
when(rr.key()).thenReturn("anotherKey");
handler.handle(rr);
verify(rr).response(null);