diff --git a/.Lib9c.Tests/Action/Common/MockKeyConverters.cs b/.Lib9c.Tests/Action/Common/MockKeyConverters.cs
deleted file mode 100644
index 44d0239eac..0000000000
--- a/.Lib9c.Tests/Action/Common/MockKeyConverters.cs
+++ /dev/null
@@ -1,96 +0,0 @@
-namespace Lib9c.Tests.Action
-{
-    using Libplanet.Crypto;
-    using Libplanet.Store.Trie;
-    using Libplanet.Types.Assets;
-
-    internal static class MockKeyConverters
-    {
-        // "___"
-        internal static readonly KeyBytes ValidatorSetKey =
-            new KeyBytes(new byte[] { _underScore, _underScore, _underScore });
-
-        private const byte _underScore = 95;  // '_'
-
-        private static readonly byte[] _conversionTable =
-        {
-            48,  // '0'
-            49,  // '1'
-            50,  // '2'
-            51,  // '3'
-            52,  // '4'
-            53,  // '5'
-            54,  // '6'
-            55,  // '7'
-            56,  // '8'
-            57,  // '9'
-            97,  // 'a'
-            98,  // 'b'
-            99,  // 'c'
-            100, // 'd'
-            101, // 'e'
-            102, // 'f'
-        };
-
-        // $"{ByteUtil.Hex(address.ByteArray)}"
-        internal static KeyBytes ToStateKey(Address address)
-        {
-            var addressBytes = address.ByteArray;
-            byte[] buffer = new byte[addressBytes.Length * 2];
-            for (int i = 0; i < addressBytes.Length; i++)
-            {
-                buffer[i * 2] = _conversionTable[addressBytes[i] >> 4];
-                buffer[i * 2 + 1] = _conversionTable[addressBytes[i] & 0xf];
-            }
-
-            return new KeyBytes(buffer);
-        }
-
-        // $"_{ByteUtil.Hex(address.ByteArray)}_{ByteUtil.Hex(currency.Hash.ByteArray)}"
-        internal static KeyBytes ToFungibleAssetKey(Address address, Currency currency)
-        {
-            var addressBytes = address.ByteArray;
-            var currencyBytes = currency.Hash.ByteArray;
-            byte[] buffer = new byte[addressBytes.Length * 2 + currencyBytes.Length * 2 + 2];
-
-            buffer[0] = _underScore;
-            for (int i = 0; i < addressBytes.Length; i++)
-            {
-                buffer[1 + i * 2] = _conversionTable[addressBytes[i] >> 4];
-                buffer[1 + i * 2 + 1] = _conversionTable[addressBytes[i] & 0xf];
-            }
-
-            var offset = addressBytes.Length * 2;
-            buffer[offset + 1] = _underScore;
-            for (int i = 0; i < currencyBytes.Length; i++)
-            {
-                buffer[offset + 2 + i * 2] = _conversionTable[currencyBytes[i] >> 4];
-                buffer[offset + 2 + i * 2 + 1] = _conversionTable[currencyBytes[i] & 0xf];
-            }
-
-            return new KeyBytes(buffer);
-        }
-
-        internal static KeyBytes ToFungibleAssetKey(
-            (Address Address, Currency Currency) pair) =>
-            ToFungibleAssetKey(pair.Address, pair.Currency);
-
-        // $"__{ByteUtil.Hex(currency.Hash.ByteArray)}"
-        internal static KeyBytes ToTotalSupplyKey(Currency currency)
-        {
-            var currencyBytes = currency.Hash.ByteArray;
-            byte[] buffer = new byte[currencyBytes.Length * 2 + 2];
-
-            buffer[0] = _underScore;
-            buffer[1] = _underScore;
-
-            for (int i = 0; i < currencyBytes.Length; i++)
-            {
-                buffer[2 + i * 2] = _conversionTable[currencyBytes[i] >> 4];
-                buffer[2 + i * 2 + 1] = _conversionTable[currencyBytes[i] & 0xf];
-            }
-
-            return new KeyBytes(buffer);
-        }
-    }
-}