feat: Add unit tests and fakes for Crestron environment and data store

- Introduced `FakeCrestronEnvironment` and `FakeEthernetHelper` for testing purposes.
- Implemented `InMemoryCrestronDataStore` to facilitate unit tests for data storage.
- Created `DebugServiceTests` to validate the behavior of debug-related services.
- Added project files for unit tests targeting .NET 9.0 with necessary dependencies.
- Developed production adapters (`CrestronConsoleAdapter`, `CrestronDataStoreAdapter`, `CrestronEnvironmentAdapter`, `CrestronEthernetAdapter`) to interface with the Crestron SDK.
- Updated `Debug` class to utilize injected service abstractions instead of direct SDK calls.
- Enhanced `ControlSystem` initialization to register service adapters before usage.

src/PepperDash.Essentials.Core.Tests/Config/ConfigServiceFakesTests.cs

@@ -0,0 +1,73 @@
+using FluentAssertions;
+using PepperDash.Core.Abstractions;
+using PepperDash.Core.Tests.Fakes;
+using Xunit;
+
+namespace PepperDash.Essentials.Core.Tests.Config;
+
+/// <summary>
+/// Tests for the configuration loading abstractions.
+/// These verify behaviour of the test fakes and interfaces independently of
+/// any Crestron SDK types (ConfigReader itself will be tested here once it
+/// is migrated from Crestron.SimplSharp.CrestronIO to System.IO — see plan Phase 4).
+/// </summary>
+public class ConfigServiceFakesTests
+{
+    [Fact]
+    public void DataStore_MultipleKeys_AreStoredIndependently()
+    {
+        var store = new InMemoryCrestronDataStore();
+        store.InitStore();
+
+        store.SetLocalInt("KeyA", 1);
+        store.SetLocalInt("KeyB", 2);
+
+        store.TryGetLocalInt("KeyA", out var a);
+        store.TryGetLocalInt("KeyB", out var b);
+
+        a.Should().Be(1);
+        b.Should().Be(2);
+    }
+
+    [Fact]
+    public void DataStore_OverwriteKey_ReturnsNewValue()
+    {
+        var store = new InMemoryCrestronDataStore();
+        store.SetLocalInt("Level", 1);
+        store.SetLocalInt("Level", 5);
+
+        store.TryGetLocalInt("Level", out var level);
+        level.Should().Be(5);
+    }
+
+    [Fact]
+    public void FakeEnvironment_CanBeConfiguredForServer()
+    {
+        var env = new FakeCrestronEnvironment
+        {
+            DevicePlatform = DevicePlatform.Server,
+            ApplicationNumber = 1,
+            RoomId = 42,
+        };
+
+        env.DevicePlatform.Should().Be(DevicePlatform.Server);
+        env.RoomId.Should().Be(42u);
+    }
+
+    [Fact]
+    public void FakeEthernetHelper_SeedAndRetrieve()
+    {
+        var eth = new FakeEthernetHelper()
+            .Seed(EthernetParameterType.GetCurrentIpAddress, "192.168.1.100")
+            .Seed(EthernetParameterType.GetHostname, "MC4-TEST");
+
+        eth.GetEthernetParameter(EthernetParameterType.GetCurrentIpAddress, 0)
+            .Should().Be("192.168.1.100");
+
+        eth.GetEthernetParameter(EthernetParameterType.GetHostname, 0)
+            .Should().Be("MC4-TEST");
+
+        eth.GetEthernetParameter(EthernetParameterType.GetDomainName, 0)
+            .Should().BeEmpty("unseeded parameter should return empty string");
+    }
+}

src/PepperDash.Essentials.Core.Tests/PepperDash.Essentials.Core.Tests.csproj

@@ -0,0 +1,27 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <IsPackable>false</IsPackable>
+    <GeneratePackageOnBuild>false</GeneratePackageOnBuild>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+    <PackageReference Include="NSubstitute" Version="5.3.0" />
+    <PackageReference Include="FluentAssertions" Version="7.0.0" />
+  </ItemGroup>
+
+  <!-- Reference the Abstractions project only — no Crestron SDK dependency -->
+  <ItemGroup>
+    <ProjectReference Include="..\PepperDash.Core.Abstractions\PepperDash.Core.Abstractions.csproj" />
+    <!-- Reference Core.Tests to share the Fakes folder -->
+    <ProjectReference Include="..\PepperDash.Core.Tests\PepperDash.Core.Tests.csproj" />
+  </ItemGroup>
+</Project>