private void mergeTest(RheaKVStore store) {
        // regions: 1 -> [null, g), 2 -> [g, t), 3 -> [t, null)
        String key = "key";
        byte[] value = store.bGet(key);
        assertNull(value);

        store.bMerge(key, "aa");
        store.bMerge(key, "bb");
        store.bMerge(key, "cc");
        value = store.bGet(key);
        assertArrayEquals(value, BytesUtil.writeUtf8("aa,bb,cc"));
    }
Test method: {@link RheaKVStore#merge(String, String)}
jraft-rheakv/rheakv-core/src/test/java/com/alipay/sofa/jraft/rhea/storage/rhea/AbstractRheaKVStoreTest.java