diff --git a/NEW/tests/JdeScoping.Client.Tests/JdeScoping.Client.Tests.csproj b/NEW/tests/JdeScoping.Client.Tests/JdeScoping.Client.Tests.csproj
index a297514..ae0028e 100644
--- a/NEW/tests/JdeScoping.Client.Tests/JdeScoping.Client.Tests.csproj
+++ b/NEW/tests/JdeScoping.Client.Tests/JdeScoping.Client.Tests.csproj
@@ -7,6 +7,10 @@
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 
+  <ItemGroup>
+    <FrameworkReference Include="Microsoft.AspNetCore.App" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="coverlet.collector" Version="6.0.4" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
diff --git a/NEW/tests/JdeScoping.Client.Tests/Services/ApiClientBaseTests.cs b/NEW/tests/JdeScoping.Client.Tests/Services/ApiClientBaseTests.cs
index a0e8929..de45b2d 100644
--- a/NEW/tests/JdeScoping.Client.Tests/Services/ApiClientBaseTests.cs
+++ b/NEW/tests/JdeScoping.Client.Tests/Services/ApiClientBaseTests.cs
@@ -36,4 +36,85 @@ public class ApiClientBaseTests
         result.Value.Id.ShouldBe(42);
         result.Value.Name.ShouldBe("Test");
     }
+
+    [Fact]
+    public async Task GetAsync_Returns404_MapsToNotFound()
+    {
+        // Arrange
+        _mockHttp.When("/api/test")
+            .Respond(HttpStatusCode.NotFound);
+
+        // Act
+        var result = await _client.GetAsync<TestDto>("/api/test");
+
+        // Assert
+        result.IsNotFound.ShouldBeTrue();
+    }
+
+    [Fact]
+    public async Task GetAsync_Returns400_WithValidationErrors_MapsToValidationError()
+    {
+        // Arrange - use actual ValidationProblemDetails structure to match production
+        var validationProblem = new Microsoft.AspNetCore.Mvc.ValidationProblemDetails
+        {
+            Errors =
+            {
+                ["Name"] = new[] { "Name is required" },
+                ["Id"] = new[] { "Id must be positive" }
+            }
+        };
+        _mockHttp.When("/api/test")
+            .Respond(HttpStatusCode.BadRequest, "application/json", JsonSerializer.Serialize(validationProblem, new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.CamelCase }));
+
+        // Act
+        var result = await _client.GetAsync<TestDto>("/api/test");
+
+        // Assert
+        result.IsValidationError.ShouldBeTrue();
+        result.ValidationError.FieldErrors.ShouldContainKey("Name");
+        result.ValidationError.FieldErrors["Name"].ShouldContain("Name is required");
+    }
+
+    [Fact]
+    public async Task GetAsync_Returns401_MapsToUnauthorized()
+    {
+        // Arrange
+        _mockHttp.When("/api/test")
+            .Respond(HttpStatusCode.Unauthorized);
+
+        // Act
+        var result = await _client.GetAsync<TestDto>("/api/test");
+
+        // Assert
+        result.IsUnauthorized.ShouldBeTrue();
+    }
+
+    [Fact]
+    public async Task GetAsync_Returns403_MapsToForbidden()
+    {
+        // Arrange
+        _mockHttp.When("/api/test")
+            .Respond(HttpStatusCode.Forbidden);
+
+        // Act
+        var result = await _client.GetAsync<TestDto>("/api/test");
+
+        // Assert
+        result.IsForbidden.ShouldBeTrue();
+    }
+
+    [Fact]
+    public async Task GetAsync_Returns500_MapsToApiError()
+    {
+        // Arrange
+        _mockHttp.When("/api/test")
+            .Respond(HttpStatusCode.InternalServerError, "text/plain", "Internal Server Error");
+
+        // Act
+        var result = await _client.GetAsync<TestDto>("/api/test");
+
+        // Assert
+        result.IsError.ShouldBeTrue();
+        result.Error.StatusCode.ShouldBe(500);
+    }
 }