diff --git a/DbFirst.BlazorWebApp/Components/CatalogsGrid.razor b/DbFirst.BlazorWebApp/Components/CatalogsGrid.razor
index e3d5372..f2602a0 100644
--- a/DbFirst.BlazorWebApp/Components/CatalogsGrid.razor
+++ b/DbFirst.BlazorWebApp/Components/CatalogsGrid.razor
@@ -1,5 +1,5 @@
 @inherits BandGridBase<CatalogReadDto>
-@inject CatalogApiClient Api
+@inject ICatalogApiClient Api
 
 @if (!string.IsNullOrWhiteSpace(errorMessage))
 {
diff --git a/DbFirst.BlazorWebApp/Components/MassDataGrid.razor b/DbFirst.BlazorWebApp/Components/MassDataGrid.razor
index 0e93895..7fb68a1 100644
--- a/DbFirst.BlazorWebApp/Components/MassDataGrid.razor
+++ b/DbFirst.BlazorWebApp/Components/MassDataGrid.razor
@@ -1,5 +1,5 @@
 @inherits BandGridBase<MassDataReadDto>
-@inject MassDataApiClient Api
+@inject IMassDataApiClient Api
 
 @if (!string.IsNullOrWhiteSpace(errorMessage))
 {
diff --git a/DbFirst.BlazorWebApp/Components/Pages/Dashboard.razor b/DbFirst.BlazorWebApp/Components/Pages/Dashboard.razor
index 727b154..0284f19 100644
--- a/DbFirst.BlazorWebApp/Components/Pages/Dashboard.razor
+++ b/DbFirst.BlazorWebApp/Components/Pages/Dashboard.razor
@@ -3,7 +3,7 @@
 @implements IAsyncDisposable
 @inject IOptions<AppSettings> AppSettingsOptions
 @inject NavigationManager Navigation
-@inject DashboardApiClient DashboardApi
+@inject IDashboardApiClient DashboardApi
 
 <PageTitle>Dashboards</PageTitle>
 
diff --git a/DbFirst.BlazorWebApp/Program.cs b/DbFirst.BlazorWebApp/Program.cs
index 255352c..1184383 100644
--- a/DbFirst.BlazorWebApp/Program.cs
+++ b/DbFirst.BlazorWebApp/Program.cs
@@ -21,10 +21,10 @@ void ConfigureClient(HttpClient client)
         client.BaseAddress = new Uri(apiBaseUrl);
 }
 
-builder.Services.AddHttpClient<CatalogApiClient>(ConfigureClient);
-builder.Services.AddHttpClient<DashboardApiClient>(ConfigureClient);
-builder.Services.AddHttpClient<MassDataApiClient>(ConfigureClient);
-builder.Services.AddHttpClient<LayoutApiClient>(ConfigureClient);
+builder.Services.AddHttpClient<ICatalogApiClient, CatalogApiClient>(ConfigureClient);
+builder.Services.AddHttpClient<IDashboardApiClient, DashboardApiClient>(ConfigureClient);
+builder.Services.AddHttpClient<IMassDataApiClient, MassDataApiClient>(ConfigureClient);
+builder.Services.AddHttpClient<ILayoutApiClient, LayoutApiClient>(ConfigureClient);
 
 var app = builder.Build();
 
diff --git a/DbFirst.BlazorWebApp/Services/BandLayoutService.cs b/DbFirst.BlazorWebApp/Services/BandLayoutService.cs
index 0082f80..5d0414b 100644
--- a/DbFirst.BlazorWebApp/Services/BandLayoutService.cs
+++ b/DbFirst.BlazorWebApp/Services/BandLayoutService.cs
@@ -5,7 +5,7 @@ using System.Text.Json;
 
 namespace DbFirst.BlazorWebApp.Services
 {
-    public class BandLayoutService(LayoutApiClient layoutApi, IJSRuntime jsRuntime)
+    public class BandLayoutService(ILayoutApiClient layoutApi, IJSRuntime jsRuntime)
     {
         private const string LayoutUserStorageKey = "layoutUser";
         private readonly JsonSerializerOptions _jsonOptions = new(JsonSerializerDefaults.Web);
diff --git a/DbFirst.BlazorWebApp/Services/CatalogApiClient.cs b/DbFirst.BlazorWebApp/Services/CatalogApiClient.cs
index f5a3b9d..0c97a9f 100644
--- a/DbFirst.BlazorWebApp/Services/CatalogApiClient.cs
+++ b/DbFirst.BlazorWebApp/Services/CatalogApiClient.cs
@@ -4,7 +4,7 @@ using DbFirst.BlazorWebApp.Models;
 
 namespace DbFirst.BlazorWebApp.Services;
 
-public class CatalogApiClient
+public class CatalogApiClient : ICatalogApiClient
 {
     private readonly HttpClient _httpClient;
     private const string Endpoint = "api/catalogs";
diff --git a/DbFirst.BlazorWebApp/Services/DashboardApiClient.cs b/DbFirst.BlazorWebApp/Services/DashboardApiClient.cs
index cfc0773..9ea41f8 100644
--- a/DbFirst.BlazorWebApp/Services/DashboardApiClient.cs
+++ b/DbFirst.BlazorWebApp/Services/DashboardApiClient.cs
@@ -3,7 +3,7 @@ using DbFirst.BlazorWebApp.Models;
 
 namespace DbFirst.BlazorWebApp.Services;
 
-public class DashboardApiClient
+public class DashboardApiClient : IDashboardApiClient
 {
     private readonly HttpClient _httpClient;
     private const string Endpoint = "api/dashboard/dashboards";
diff --git a/DbFirst.BlazorWebApp/Services/ICatalogApiClient.cs b/DbFirst.BlazorWebApp/Services/ICatalogApiClient.cs
new file mode 100644
index 0000000..c307205
--- /dev/null
+++ b/DbFirst.BlazorWebApp/Services/ICatalogApiClient.cs
@@ -0,0 +1,12 @@
+using DbFirst.BlazorWebApp.Models;
+
+namespace DbFirst.BlazorWebApp.Services;
+
+public interface ICatalogApiClient
+{
+    Task<List<CatalogReadDto>> GetAllAsync();
+    Task<CatalogReadDto?> GetByIdAsync(int id);
+    Task<ApiResult<CatalogReadDto?>> CreateAsync(CatalogWriteDto dto);
+    Task<ApiResult<bool>> UpdateAsync(int id, CatalogWriteDto dto);
+    Task<ApiResult<bool>> DeleteAsync(int id);
+}
\ No newline at end of file
diff --git a/DbFirst.BlazorWebApp/Services/IDashboardApiClient.cs b/DbFirst.BlazorWebApp/Services/IDashboardApiClient.cs
new file mode 100644
index 0000000..fba9d7b
--- /dev/null
+++ b/DbFirst.BlazorWebApp/Services/IDashboardApiClient.cs
@@ -0,0 +1,9 @@
+using DbFirst.BlazorWebApp.Models;
+
+namespace DbFirst.BlazorWebApp.Services
+{
+    public interface IDashboardApiClient
+    {
+        Task<List<DashboardInfoDto>> GetAllAsync();
+    }
+}
diff --git a/DbFirst.BlazorWebApp/Services/ILayoutApiClient.cs b/DbFirst.BlazorWebApp/Services/ILayoutApiClient.cs
new file mode 100644
index 0000000..a39116e
--- /dev/null
+++ b/DbFirst.BlazorWebApp/Services/ILayoutApiClient.cs
@@ -0,0 +1,11 @@
+using DbFirst.BlazorWebApp.Models;
+
+namespace DbFirst.BlazorWebApp.Services
+{
+    public interface ILayoutApiClient
+    {
+        Task<LayoutDto?> GetAsync(string layoutType, string layoutKey, string userName);
+        Task<LayoutDto> UpsertAsync(LayoutDto dto);
+        Task DeleteAsync(string layoutType, string layoutKey, string userName);
+    }
+}
diff --git a/DbFirst.BlazorWebApp/Services/IMassDataApiClient.cs b/DbFirst.BlazorWebApp/Services/IMassDataApiClient.cs
new file mode 100644
index 0000000..13f3e95
--- /dev/null
+++ b/DbFirst.BlazorWebApp/Services/IMassDataApiClient.cs
@@ -0,0 +1,12 @@
+using DbFirst.BlazorWebApp.Models;
+
+namespace DbFirst.BlazorWebApp.Services
+{
+    public interface IMassDataApiClient
+    {
+        Task<int> GetCountAsync();
+        Task<List<MassDataReadDto>> GetAllAsync(int? skip, int? take);
+        Task<ApiResult<MassDataReadDto?>> UpsertAsync(MassDataWriteDto dto);
+        Task<MassDataReadDto?> GetByCustomerNameAsync(string customerName);
+    }
+}
diff --git a/DbFirst.BlazorWebApp/Services/LayoutApiClient.cs b/DbFirst.BlazorWebApp/Services/LayoutApiClient.cs
index 0a863e8..ca83973 100644
--- a/DbFirst.BlazorWebApp/Services/LayoutApiClient.cs
+++ b/DbFirst.BlazorWebApp/Services/LayoutApiClient.cs
@@ -3,7 +3,7 @@ using DbFirst.BlazorWebApp.Models;
 
 namespace DbFirst.BlazorWebApp.Services;
 
-public class LayoutApiClient
+public class LayoutApiClient : ILayoutApiClient
 {
     private readonly HttpClient _httpClient;
     private const string Endpoint = "api/layouts";
diff --git a/DbFirst.BlazorWebApp/Services/MassDataApiClient.cs b/DbFirst.BlazorWebApp/Services/MassDataApiClient.cs
index 4735881..1f45682 100644
--- a/DbFirst.BlazorWebApp/Services/MassDataApiClient.cs
+++ b/DbFirst.BlazorWebApp/Services/MassDataApiClient.cs
@@ -3,7 +3,7 @@ using DbFirst.BlazorWebApp.Models;
 
 namespace DbFirst.BlazorWebApp.Services;
 
-public class MassDataApiClient
+public class MassDataApiClient : IMassDataApiClient
 {
     private readonly HttpClient _httpClient;
     private const string Endpoint = "api/massdata";