public void T002_ScanDirections()
        {
            LayerManager db = new LayerManager(InitMode.NEW_REGION, "c:\\BENDtst\\3");

            var rk_a = new RecordKey().appendParsedKey(".a");
            var rk_b = new RecordKey().appendParsedKey(".b");
            string[] keys = { ".a", ".b" };
            foreach (var key in keys) {
                db.setValueParsed(key, "valueof:" + key);
            }

            {
                var rec = db.FindNext(rk_a, false);
                Assert.AreEqual(rk_b, rec.Key, "simple FindNext");
            }

            {
                var rec = db.FindPrev(rk_b, false);
                Assert.AreEqual(rk_a, rec.Key, "simple FindPrev");
            }

            var scan_range = new ScanRange<RecordKey>(rk_a, rk_b, null);

            // scan forward
            int count = 0;
            foreach (var row in db.scanForward(scan_range)) {
                Console.WriteLine("forward scan: " + row);
                if (count == keys.Length) {
                    Assert.Fail("too many keys returned in scan");
                }
                Assert.AreEqual(new RecordKeyType_String(keys[count]), row.Key.key_parts[0], "forward scan mistake");
                count++;
            }
            if (count != keys.Length) {
                Assert.Fail("not enough keys returned in scan");
            }

            // scan backward

            count = keys.Length;
            foreach (var row in db.scanBackward(scan_range)) {
                Console.WriteLine("backward scan: " + row);
                if (count == 0) {
                    Assert.Fail("too many keys returned in scan backward");
                }
                count--;
                Assert.AreEqual(new RecordKeyType_String(keys[count]), row.Key.key_parts[0], "backward scan mistake");
            }
            if (count != 0) {
                Assert.Fail("not enough keys returned in scan");
            }
        }