diff --git a/Mimir.MongoDB/Repositories/BalanceRepository.cs b/Mimir.MongoDB/Repositories/BalanceRepository.cs
index da2303a7..cb0ff279 100644
--- a/Mimir.MongoDB/Repositories/BalanceRepository.cs
+++ b/Mimir.MongoDB/Repositories/BalanceRepository.cs
@@ -1,13 +1,18 @@
 using Libplanet.Crypto;
 using Libplanet.Types.Assets;
-using Mimir.MongoDB.Exceptions;
 using Mimir.MongoDB.Bson;
+using Mimir.MongoDB.Exceptions;
 using Mimir.MongoDB.Services;
 using MongoDB.Driver;
 
 namespace Mimir.MongoDB.Repositories;
 
-public class BalanceRepository(IMongoDbService dbService)
+public interface IBalanceRepository
+{
+    Task<BalanceDocument> GetByAddressAsync(Currency currency, Address address);
+}
+
+public class BalanceRepository(IMongoDbService dbService) : IBalanceRepository
 {
     public async Task<BalanceDocument> GetByAddressAsync(Currency currency, Address address)
     {
diff --git a/Mimir.Tests/QueryTests/BalanceQueryTest.GraphQL_Query_Balance_CRYSTAL_Returns_CorrectValue.verified.txt b/Mimir.Tests/QueryTests/BalanceQueryTest.GraphQL_Query_Balance_CRYSTAL_Returns_CorrectValue.verified.txt
new file mode 100644
index 00000000..93f63e46
--- /dev/null
+++ b/Mimir.Tests/QueryTests/BalanceQueryTest.GraphQL_Query_Balance_CRYSTAL_Returns_CorrectValue.verified.txt
@@ -0,0 +1,5 @@
+{
+  "data": {
+    "balance": "fgfgf"
+  }
+}
\ No newline at end of file
diff --git a/Mimir.Tests/QueryTests/BalanceQueryTest.GraphQL_Query_Balance_NCG_Returns_CorrectValue.verified.txt b/Mimir.Tests/QueryTests/BalanceQueryTest.GraphQL_Query_Balance_NCG_Returns_CorrectValue.verified.txt
new file mode 100644
index 00000000..93f63e46
--- /dev/null
+++ b/Mimir.Tests/QueryTests/BalanceQueryTest.GraphQL_Query_Balance_NCG_Returns_CorrectValue.verified.txt
@@ -0,0 +1,5 @@
+{
+  "data": {
+    "balance": "fgfgf"
+  }
+}
\ No newline at end of file
diff --git a/Mimir.Tests/QueryTests/BalanceQueryTest.GraphQL_Query_Balance_Throws_When_No_Inputs_Provided.verified.txt b/Mimir.Tests/QueryTests/BalanceQueryTest.GraphQL_Query_Balance_Throws_When_No_Inputs_Provided.verified.txt
new file mode 100644
index 00000000..dac2b846
--- /dev/null
+++ b/Mimir.Tests/QueryTests/BalanceQueryTest.GraphQL_Query_Balance_Throws_When_No_Inputs_Provided.verified.txt
@@ -0,0 +1,17 @@
+{
+  "errors": [
+    {
+      "message": "Either currency or currencyTicker must be provided.",
+      "locations": [
+        {
+          "line": 2,
+          "column": 7
+        }
+      ],
+      "path": [
+        "balance"
+      ]
+    }
+  ],
+  "data": null
+}
\ No newline at end of file
diff --git a/Mimir.Tests/QueryTests/BalanceQueryTest.cs b/Mimir.Tests/QueryTests/BalanceQueryTest.cs
new file mode 100644
index 00000000..0893901f
--- /dev/null
+++ b/Mimir.Tests/QueryTests/BalanceQueryTest.cs
@@ -0,0 +1,80 @@
+using HotChocolate.AspNetCore;
+using Lib9c.GraphQL.Extensions;
+using Libplanet.Crypto;
+using Mimir.MongoDB.Bson;
+using Mimir.MongoDB.Repositories;
+using Moq;
+
+namespace Mimir.Tests.QueryTests;
+
+public class BalanceQueryTest
+{
+    [Fact]
+    public async Task GraphQL_Query_Balance_CRYSTAL_Returns_CorrectValue()
+    {
+        var mockAddress = new Address("0x0000000000000000000000000000000000000000");
+        var mockRepo = new Mock<IBalanceRepository>();
+
+        mockRepo
+            .Setup(repo => repo.GetByAddressAsync("CRYSTAL".ToCurrency(), mockAddress))
+            .ReturnsAsync(new BalanceDocument(1, new Address(), "fgfgf"));
+        
+        var serviceProvider = TestServices.Builder
+            .With(mockRepo.Object)
+            .Build();
+
+        var query = $$"""
+                          query {
+                            balance(currencyTicker: "CRYSTAL", address: "{{mockAddress}}")
+                          }
+                      """;
+
+        var result = await TestServices.ExecuteRequestAsync(serviceProvider, b => b.SetDocument(query));
+
+        await Verify(result);
+    }
+
+    [Fact]
+    public async Task GraphQL_Query_Balance_NCG_Returns_CorrectValue()
+    {
+        var mockAddress = new Address("0x0000000000000000000000000000000000000000");
+        var mockRepo = new Mock<IBalanceRepository>();
+
+        mockRepo
+            .Setup(repo => repo.GetByAddressAsync("NCG".ToCurrency(), mockAddress))
+            .ReturnsAsync(new BalanceDocument(1, new Address(), "fgfgf"));
+
+        var serviceProvider = TestServices.Builder
+            .With(mockRepo.Object)
+            .Build();
+
+        var query = $$"""
+                          query {
+                            balance(currencyTicker: "NCG", address: "{{mockAddress}}")
+                          }
+                      """;
+
+        var result = await TestServices.ExecuteRequestAsync(serviceProvider, b => b.SetDocument(query));
+
+        await Verify(result);
+    }
+    
+    [Fact]
+    public async Task GraphQL_Query_Balance_Throws_When_No_Inputs_Provided()
+    {
+        var mockRepo = new Mock<IBalanceRepository>();
+        
+        var serviceProvider = TestServices.Builder
+            .With(mockRepo.Object)
+            .Build();
+
+        var query = $$"""
+                          query {
+                            balance(address: "0x0000000000000000000000000000000000000000")
+                          }
+                      """;
+
+        var result = await TestServices.ExecuteRequestAsync(serviceProvider, b => b.SetDocument(query));
+        await Verify(result);
+    }
+}
\ No newline at end of file
diff --git a/Mimir/GraphQL/Queries/Query.cs b/Mimir/GraphQL/Queries/Query.cs
index 7b66e1b4..8e5bd933 100644
--- a/Mimir/GraphQL/Queries/Query.cs
+++ b/Mimir/GraphQL/Queries/Query.cs
@@ -60,7 +60,7 @@ public async Task<string> GetBalanceAsync(
         CurrencyInput? currency,
         string? currencyTicker,
         Address address,
-        [Service] BalanceRepository repo)
+        [Service] IBalanceRepository repo)
     {
         if (currency is not null)
         {
diff --git a/Mimir/Program.cs b/Mimir/Program.cs
index e4d76128..ca4e6ec4 100644
--- a/Mimir/Program.cs
+++ b/Mimir/Program.cs
@@ -10,6 +10,7 @@
 using Mimir.MongoDB.Repositories;
 using Mimir.Options;
 using Mimir.MongoDB.Services;
+using BalanceRepository = Mimir.MongoDB.Repositories.BalanceRepository;
 
 var builder = WebApplication.CreateBuilder(args);
 
@@ -42,7 +43,7 @@
 builder.Services.AddSingleton<ArenaRepository>();
 builder.Services.AddSingleton<ArenaParticipantRepository>();
 builder.Services.AddSingleton<IAvatarRepository, AvatarRepository>();
-builder.Services.AddSingleton<BalanceRepository>();
+builder.Services.AddSingleton<IBalanceRepository, BalanceRepository>();
 builder.Services.AddSingleton<ICollectionRepository,CollectionRepository>();
 builder.Services.AddSingleton<IDailyRewardRepository, DailyRewardRepository>();
 builder.Services.AddSingleton<IInventoryRepository, InventoryRepository>();