private void putIfAbsentTest(RheaKVStore store) {
        // regions: 1 -> [null, g), 2 -> [g, null)
        byte[] key = makeKey("u_put_if_absent_test");
        checkRegion(store, key, 2);
        byte[] value = makeValue("put_if_absent_test_value");
        byte[] newValue = makeValue("put_if_absent_test_value_1");
        byte[] oldValue = store.bPutIfAbsent(key, value);
        assertNull(oldValue);
        oldValue = store.bPutIfAbsent(key, newValue);
        assertArrayEquals(value, oldValue);
    }
Test method: {@link RheaKVStore#putIfAbsent(byte[], byte[])}
jraft-rheakv/rheakv-core/src/test/java/com/alipay/sofa/jraft/rhea/storage/rhea/AbstractRheaKVStoreTest.java