diff --git a/src/PepperDash.Core.Abstractions/ICrestronEnvironment.cs b/src/PepperDash.Core.Abstractions/ICrestronEnvironment.cs
index c31fb3f6..1e73c83f 100644
--- a/src/PepperDash.Core.Abstractions/ICrestronEnvironment.cs
+++ b/src/PepperDash.Core.Abstractions/ICrestronEnvironment.cs
@@ -29,6 +29,13 @@ public interface ICrestronEnvironment
 
     /// <summary>Gets the application root directory path.</summary>
     string GetApplicationRootDirectory();
+
+    /// <summary>
+    /// Returns <c>true</c> when running on real Crestron hardware.
+    /// Returns <c>false</c> in test / dev environments so that SDK-specific
+    /// sinks and enrichers can be safely skipped.
+    /// </summary>
+    bool IsHardwareRuntime { get; }
 }
 
 /// <summary>
diff --git a/src/PepperDash.Core.Tests/Devices/DeviceTests.cs b/src/PepperDash.Core.Tests/Devices/DeviceTests.cs
new file mode 100644
index 00000000..2450e401
--- /dev/null
+++ b/src/PepperDash.Core.Tests/Devices/DeviceTests.cs
@@ -0,0 +1,323 @@
+using FluentAssertions;
+using PepperDash.Core;
+using Xunit;
+
+namespace PepperDash.Core.Tests.Devices;
+
+/// <summary>
+/// Tests for <see cref="Device"/> — the base class for all PepperDash devices.
+/// These run without Crestron hardware; Debug is initialized with fakes via TestInitializer.
+/// </summary>
+public class DeviceTests
+{
+    // -----------------------------------------------------------------------
+    // Construction
+    // -----------------------------------------------------------------------
+
+    [Fact]
+    public void Constructor_SingleArg_SetsKey()
+    {
+        var device = new Device("my-device");
+
+        device.Key.Should().Be("my-device");
+    }
+
+    [Fact]
+    public void Constructor_SingleArg_SetsNameToEmpty()
+    {
+        var device = new Device("my-device");
+
+        device.Name.Should().BeEmpty();
+    }
+
+    [Fact]
+    public void Constructor_TwoArg_SetsKeyAndName()
+    {
+        var device = new Device("my-device", "My Device");
+
+        device.Key.Should().Be("my-device");
+        device.Name.Should().Be("My Device");
+    }
+
+    [Fact]
+    public void Constructor_KeyWithDot_StillSetsKey()
+    {
+        // The dot triggers a debug log warning but must not prevent construction.
+        var device = new Device("parent.child");
+
+        device.Key.Should().Be("parent.child");
+    }
+
+    // -----------------------------------------------------------------------
+    // ToString
+    // -----------------------------------------------------------------------
+
+    [Fact]
+    public void ToString_WithName_FormatsKeyDashName()
+    {
+        var device = new Device("cam-01", "Front Camera");
+
+        device.ToString().Should().Be("cam-01 - Front Camera");
+    }
+
+    [Fact]
+    public void ToString_WithoutName_UsesDashPlaceholder()
+    {
+        var device = new Device("cam-01");
+
+        device.ToString().Should().Be("cam-01 - ---");
+    }
+
+    // -----------------------------------------------------------------------
+    // DefaultDevice
+    // -----------------------------------------------------------------------
+
+    [Fact]
+    public void DefaultDevice_IsNotNull()
+    {
+        Device.DefaultDevice.Should().NotBeNull();
+    }
+
+    [Fact]
+    public void DefaultDevice_HasKeyDefault()
+    {
+        Device.DefaultDevice.Key.Should().Be("Default");
+    }
+
+    // -----------------------------------------------------------------------
+    // CustomActivate / Activate / Deactivate / Initialize
+    // -----------------------------------------------------------------------
+
+    [Fact]
+    public void CustomActivate_DefaultReturnTrue()
+    {
+        var device = new TestDevice("d1");
+
+        device.CallCustomActivate().Should().BeTrue();
+    }
+
+    [Fact]
+    public void Deactivate_DefaultReturnsTrue()
+    {
+        var device = new Device("d1");
+
+        device.Deactivate().Should().BeTrue();
+    }
+
+    [Fact]
+    public void Activate_CallsCustomActivate_AndReturnsItsResult()
+    {
+        var stub = new ActivateTrackingDevice("d1", result: false);
+
+        stub.Activate().Should().BeFalse();
+        stub.CustomActivateCalled.Should().BeTrue();
+    }
+
+    [Fact]
+    public void Activate_TrueWhenCustomActivateReturnsTrue()
+    {
+        var stub = new ActivateTrackingDevice("d1", result: true);
+
+        stub.Activate().Should().BeTrue();
+    }
+
+    [Fact]
+    public void Initialize_DoesNotThrow()
+    {
+        var device = new TestDevice("d1");
+        var act = () => device.CallInitialize();
+
+        act.Should().NotThrow();
+    }
+
+    // -----------------------------------------------------------------------
+    // PreActivate
+    // -----------------------------------------------------------------------
+
+    [Fact]
+    public void PreActivate_NoActions_DoesNotThrow()
+    {
+        var device = new TestDevice("d1");
+        var act = () => device.PreActivate();
+
+        act.Should().NotThrow();
+    }
+
+    [Fact]
+    public void PreActivate_RunsRegisteredActionsInOrder()
+    {
+        var device = new TestDevice("d1");
+        var order = new List<int>();
+
+        device.AddPreActivationAction(() => order.Add(1));
+        device.AddPreActivationAction(() => order.Add(2));
+        device.AddPreActivationAction(() => order.Add(3));
+
+        device.PreActivate();
+
+        order.Should().Equal(1, 2, 3);
+    }
+
+    [Fact]
+    public void PreActivate_ContinuesAfterFaultingAction()
+    {
+        var device = new TestDevice("d1");
+        var reached = false;
+
+        device.AddPreActivationAction(() => throw new InvalidOperationException("boom"));
+        device.AddPreActivationAction(() => reached = true);
+
+        var act = () => device.PreActivate();
+
+        act.Should().NotThrow("exceptions in individual actions must be caught internally");
+        reached.Should().BeTrue("actions after a faulting action must still run");
+    }
+
+    // -----------------------------------------------------------------------
+    // PostActivate
+    // -----------------------------------------------------------------------
+
+    [Fact]
+    public void PostActivate_NoActions_DoesNotThrow()
+    {
+        var device = new TestDevice("d1");
+        var act = () => device.PostActivate();
+
+        act.Should().NotThrow();
+    }
+
+    [Fact]
+    public void PostActivate_RunsRegisteredActionsInOrder()
+    {
+        var device = new TestDevice("d1");
+        var order = new List<int>();
+
+        device.AddPostActivationAction(() => order.Add(1));
+        device.AddPostActivationAction(() => order.Add(2));
+
+        device.PostActivate();
+
+        order.Should().Equal(1, 2);
+    }
+
+    [Fact]
+    public void PostActivate_ContinuesAfterFaultingAction()
+    {
+        var device = new TestDevice("d1");
+        var reached = false;
+
+        device.AddPostActivationAction(() => throw new Exception("boom"));
+        device.AddPostActivationAction(() => reached = true);
+
+        var act = () => device.PostActivate();
+
+        act.Should().NotThrow();
+        reached.Should().BeTrue();
+    }
+
+    // -----------------------------------------------------------------------
+    // Pre and Post actions are independent lists
+    // -----------------------------------------------------------------------
+
+    [Fact]
+    public void PreActivationActions_DoNotRunOnPostActivate()
+    {
+        var device = new TestDevice("d1");
+        var preRan = false;
+
+        device.AddPreActivationAction(() => preRan = true);
+        device.PostActivate();
+
+        preRan.Should().BeFalse();
+    }
+
+    [Fact]
+    public void PostActivationActions_DoNotRunOnPreActivate()
+    {
+        var device = new TestDevice("d1");
+        var postRan = false;
+
+        device.AddPostActivationAction(() => postRan = true);
+        device.PreActivate();
+
+        postRan.Should().BeFalse();
+    }
+
+    // -----------------------------------------------------------------------
+    // OnFalse
+    // -----------------------------------------------------------------------
+
+    [Fact]
+    public void OnFalse_FiresAction_WhenBoolIsFalse()
+    {
+        var device = new Device("d1");
+        var fired = false;
+
+        device.OnFalse(false, () => fired = true);
+
+        fired.Should().BeTrue();
+    }
+
+    [Fact]
+    public void OnFalse_DoesNotFireAction_WhenBoolIsTrue()
+    {
+        var device = new Device("d1");
+        var fired = false;
+
+        device.OnFalse(true, () => fired = true);
+
+        fired.Should().BeFalse();
+    }
+
+    [Fact]
+    public void OnFalse_DoesNotFireAction_ForNonBoolType()
+    {
+        var device = new Device("d1");
+        var fired = false;
+
+        device.OnFalse("not a bool", () => fired = true);
+        device.OnFalse(0, () => fired = true);
+        device.OnFalse(null!, () => fired = true);
+
+        fired.Should().BeFalse();
+    }
+
+    // -----------------------------------------------------------------------
+    // Helpers
+    // -----------------------------------------------------------------------
+
+    /// <summary>
+    /// Exposes protected Device members so test methods can call them directly.
+    /// </summary>
+    private class TestDevice : Device
+    {
+        public TestDevice(string key) : base(key) { }
+        public TestDevice(string key, string name) : base(key, name) { }
+
+        public void AddPreActivationAction(Action act) => base.AddPreActivationAction(act);
+        public void AddPostActivationAction(Action act) => base.AddPostActivationAction(act);
+        public bool CallCustomActivate() => base.CustomActivate();
+        public void CallInitialize() => base.Initialize();
+    }
+
+    /// <summary>
+    /// Records whether CustomActivate was invoked and returns a configured result.
+    /// Used to verify Activate() correctly delegates to CustomActivate().
+    /// </summary>
+    private sealed class ActivateTrackingDevice : Device
+    {
+        private readonly bool _result;
+        public bool CustomActivateCalled { get; private set; }
+
+        public ActivateTrackingDevice(string key, bool result = true) : base(key)
+        {
+            _result = result;
+        }
+
+        protected override bool CustomActivate()
+        {
+            CustomActivateCalled = true;
+            return _result;
+        }
+    }
+}
diff --git a/src/PepperDash.Core.Tests/Fakes/CrestronEnvironmentFakes.cs b/src/PepperDash.Core.Tests/Fakes/CrestronEnvironmentFakes.cs
index 8070f849..1792206d 100644
--- a/src/PepperDash.Core.Tests/Fakes/CrestronEnvironmentFakes.cs
+++ b/src/PepperDash.Core.Tests/Fakes/CrestronEnvironmentFakes.cs
@@ -19,6 +19,9 @@ public class FakeCrestronEnvironment : ICrestronEnvironment
 
     public string GetApplicationRootDirectory() => System.IO.Path.GetTempPath();
 
+    /// <inheritdoc/>
+    public bool IsHardwareRuntime => false;
+
     /// <summary>Simulates a program status event for tests.</summary>
     public void RaiseProgramStatus(ProgramStatusEventType type) =>
         ProgramStatusChanged?.Invoke(this, new ProgramStatusEventArgs(type));
diff --git a/src/PepperDash.Core.Tests/PepperDash.Core.Tests.csproj b/src/PepperDash.Core.Tests/PepperDash.Core.Tests.csproj
index 54b74d00..9e045a89 100644
--- a/src/PepperDash.Core.Tests/PepperDash.Core.Tests.csproj
+++ b/src/PepperDash.Core.Tests/PepperDash.Core.Tests.csproj
@@ -21,5 +21,9 @@
   <!-- Reference the Abstractions project only — no Crestron SDK dependency -->
   <ItemGroup>
     <ProjectReference Include="..\PepperDash.Core.Abstractions\PepperDash.Core.Abstractions.csproj" />
+    <!-- PepperDash.Core is referenced so we can test Device and other concrete types.
+         DebugServiceRegistration.Register() is called via a [ModuleInitializer] before any
+         test runs, so Debug's static constructor uses fakes and never touches the Crestron SDK. -->
+    <ProjectReference Include="..\PepperDash.Core\PepperDash.Core.csproj" />
   </ItemGroup>
 </Project>
diff --git a/src/PepperDash.Core.Tests/TestInitializer.cs b/src/PepperDash.Core.Tests/TestInitializer.cs
new file mode 100644
index 00000000..6455ea59
--- /dev/null
+++ b/src/PepperDash.Core.Tests/TestInitializer.cs
@@ -0,0 +1,29 @@
+using System.Runtime.CompilerServices;
+using PepperDash.Core.Abstractions;
+using PepperDash.Core.Tests.Fakes;
+
+namespace PepperDash.Core.Tests;
+
+/// <summary>
+/// Runs once before any type in this assembly is accessed.
+/// Registers fake Crestron service implementations with <see cref="DebugServiceRegistration"/>
+/// so that the <c>Debug</c> static constructor uses them instead of the real Crestron SDK.
+/// This must remain a module initializer (not a test fixture) because the static constructor
+/// fires the first time <em>any</em> type in PepperDash.Core is referenced — before xUnit
+/// has a chance to run fixture setup code.
+/// </summary>
+internal static class TestInitializer
+{
+    [ModuleInitializer]
+    internal static void Initialize()
+    {
+        DebugServiceRegistration.Register(
+            new FakeCrestronEnvironment
+            {
+                DevicePlatform = DevicePlatform.Server, // avoids any appliance-only code paths
+                RuntimeEnvironment = RuntimeEnvironment.Other, // skips console command registration
+            },
+            new NoOpCrestronConsole(),
+            new InMemoryCrestronDataStore());
+    }
+}
diff --git a/src/PepperDash.Core/Adapters/CrestronEnvironmentAdapter.cs b/src/PepperDash.Core/Adapters/CrestronEnvironmentAdapter.cs
index 752e9631..62002d73 100644
--- a/src/PepperDash.Core/Adapters/CrestronEnvironmentAdapter.cs
+++ b/src/PepperDash.Core/Adapters/CrestronEnvironmentAdapter.cs
@@ -57,6 +57,9 @@ public sealed class CrestronEnvironmentAdapter : PdCore.ICrestronEnvironment
     public string GetApplicationRootDirectory() =>
         Crestron.SimplSharp.CrestronIO.Directory.GetApplicationRootDirectory();
 
+    /// <inheritdoc/>
+    public bool IsHardwareRuntime => true;
+
     private static PdCore.ProgramStatusEventType MapProgramStatus(eProgramStatusEventType type) =>
         type switch
         {
diff --git a/src/PepperDash.Core/Device.cs b/src/PepperDash.Core/Device.cs
index 70d4d97f..ff436b68 100644
--- a/src/PepperDash.Core/Device.cs
+++ b/src/PepperDash.Core/Device.cs
@@ -75,7 +75,7 @@ public class Device : IKeyName
 	/// Adds a pre activation action
 	/// </summary>
 	/// <param name="act"></param>
-	public void AddPreActivationAction(Action act)
+	protected void AddPreActivationAction(Action act)
 	{
 		if (_PreActivationActions == null)
 			_PreActivationActions = new List<Action>();
@@ -89,7 +89,7 @@ public class Device : IKeyName
 	/// <summary>
 	/// AddPostActivationAction method
 	/// </summary>
-	public void AddPostActivationAction(Action act)
+	protected void AddPostActivationAction(Action act)
 	{
 		if (_PostActivationActions == null)
 			_PostActivationActions = new List<Action>();
@@ -156,7 +156,7 @@ public class Device : IKeyName
 	/// <summary>
 	/// CustomActivate method
 	/// </summary>
-	public virtual bool CustomActivate() { return true; }
+	protected virtual bool CustomActivate() { return true; }
 
 	/// <summary>
 	/// Call to deactivate device - unlink events, etc.  Overriding classes do not
@@ -168,7 +168,7 @@ public class Device : IKeyName
 	/// <summary>
 	/// Call this method to start communications with a device. Overriding classes do not need to call base.Initialize()
 	/// </summary>
-	public virtual void Initialize()
+	protected virtual void Initialize()
 	{
 	}
 
diff --git a/src/PepperDash.Core/Logging/Debug.cs b/src/PepperDash.Core/Logging/Debug.cs
index fb0483bb..97a6e93e 100644
--- a/src/PepperDash.Core/Logging/Debug.cs
+++ b/src/PepperDash.Core/Logging/Debug.cs
@@ -96,7 +96,7 @@ public static class Debug
     /// <summary>
     /// The name of the file containing the current debug settings.
     /// </summary>
-    public static string FileName = string.Format(@"app{0}Debug.json", InitialParametersClass.ApplicationNumber);
+    public static string FileName = "app0Debug.json"; // default; updated in static ctor using _environment.ApplicationNumber
 
     /// <summary>
     /// Debug level to set for a given program.
@@ -161,6 +161,9 @@ public static class Debug
 
             IsRunningOnAppliance = _environment?.DevicePlatform == PdCore.DevicePlatform.Appliance;
 
+            // Update FileName now that _environment is available (avoids Crestron SDK ref in field initializer).
+            FileName = $"app{_environment?.ApplicationNumber ?? 0}Debug.json";
+
             _dataStore?.InitStore();
 
             consoleDebugTimer = new Timer(defaultConsoleDebugTimeoutMin * 60000) { AutoReset = false };
@@ -180,7 +183,7 @@ public static class Debug
             errorLogLevelSwitch = new LoggingLevelSwitch(initialMinimumLevel: defaultErrorLogLevel);
             fileLoggingLevelSwitch = new LoggingLevelSwitch(initialMinimumLevel: defaultFileLogLevel);
 
-            websocketSink = new DebugWebsocketSink(new JsonFormatter(renderMessage: true));
+            websocketSink = TryCreateWebsocketSink();
 
             var appRoot = _environment?.GetApplicationRootDirectory()
                 ?? System.IO.Path.GetTempPath();
@@ -200,7 +203,6 @@ public static class Debug
                 .MinimumLevel.Verbose()
                 .Enrich.FromLogContext()
                 .WriteTo.Sink(new DebugConsoleSink(new ExpressionTemplate("[{@t:yyyy-MM-dd HH:mm:ss.fff}][{@l:u4}][{App}]{#if Key is not null}[{Key}]{#end} {@m}{#if @x is not null}\r\n{@x}{#end}")), levelSwitch: consoleLoggingLevelSwitch)
-                .WriteTo.Sink(websocketSink, levelSwitch: websocketLoggingLevelSwitch)
                 .WriteTo.File(new RenderedCompactJsonFormatter(), logFilePath,
                     rollingInterval: RollingInterval.Day,
                     restrictedToMinimumLevel: LogEventLevel.Debug,
@@ -208,8 +210,12 @@ public static class Debug
                     levelSwitch: fileLoggingLevelSwitch
                 );
 
-            // Add Crestron-specific enricher and error-log sink only when running on hardware.
-            if (_environment != null)
+            // Websocket sink is null when DebugWebsocketSink failed to construct (e.g. test env).
+            if (websocketSink != null)
+                _defaultLoggerConfiguration.WriteTo.Sink(websocketSink, levelSwitch: websocketLoggingLevelSwitch);
+
+            // Add Crestron-specific enricher and error-log sink only on real hardware.
+            if (_environment?.IsHardwareRuntime == true)
             {
                 var errorLogTemplate = IsRunningOnAppliance
                     ? "{@t:fff}ms [{@l:u4}]{#if Key is not null}[{Key}]{#end} {@m}{#if @x is not null}\r\n{@x}{#end}"
@@ -271,8 +277,34 @@ public static class Debug
         {
             // _logger may not have been initialized yet — do not call LogError here.
             // _console may also be null; fall back to CrestronConsole as last resort.
+            // IMPORTANT: this catch block must not throw — any exception escaping a static
+            // constructor permanently faults the type, making the entire class unusable.
             try { _console?.PrintLine($"Exception in Debug static constructor: {ex.Message}\r\n{ex.StackTrace}"); }
-            catch { CrestronConsole.PrintLine($"Exception in Debug static constructor: {ex.Message}\r\n{ex.StackTrace}"); }
+            catch
+            {
+                try { CrestronConsole.PrintLine($"Exception in Debug static constructor: {ex.Message}\r\n{ex.StackTrace}"); }
+                catch { /* CrestronConsole unavailable (test/dev env) — swallow to keep type initializer healthy */ }
+            }
+        }
+        finally
+        {
+            // Guarantee _logger is never null — all Debug.Log* calls are safe even if the
+            // ctor failed partway through (e.g. on a dev machine without Crestron hardware).
+            _logger ??= new LoggerConfiguration().MinimumLevel.Fatal().CreateLogger();
+        }
+    }
+
+    /// <summary>Creates the WebSocket sink, returning null if construction fails in a test/dev environment.</summary>
+    private static DebugWebsocketSink? TryCreateWebsocketSink()
+    {
+        try
+        {
+            return new DebugWebsocketSink(new JsonFormatter(renderMessage: true));
+        }
+        catch
+        {
+            _console?.PrintLine("DebugWebsocketSink could not be created in this environment; websocket logging disabled.");
+            return null;
         }
     }
 
diff --git a/src/PepperDash.Core/Logging/DebugWebsocketSink.cs b/src/PepperDash.Core/Logging/DebugWebsocketSink.cs
index 6f1aee18..52d61896 100644
--- a/src/PepperDash.Core/Logging/DebugWebsocketSink.cs
+++ b/src/PepperDash.Core/Logging/DebugWebsocketSink.cs
@@ -91,13 +91,18 @@ public class DebugWebsocketSink : ILogEventSink, IKeyed
         if (!File.Exists(CertPath))
             CreateCert();
 
-        CrestronEnvironment.ProgramStatusEventHandler += type =>
+        try
         {
-            if (type == eProgramStatusEventType.Stopping)
+            CrestronEnvironment.ProgramStatusEventHandler += type =>
             {
-                StopServer();
-            }
-        };
+                if (type == eProgramStatusEventType.Stopping)
+                    StopServer();
+            };
+        }
+        catch
+        {
+            // CrestronEnvironment is not available in test / dev environments — safe to skip.
+        }
     }
 
     private static void CreateCert()
diff --git a/src/PepperDash.Essentials.MobileControl.Messengers/Messengers/DeviceStateMessageBase.cs b/src/PepperDash.Essentials.MobileControl.Messengers/Messengers/DeviceStateMessageBase.cs
index 87f19e3f..1e538a31 100644
--- a/src/PepperDash.Essentials.MobileControl.Messengers/Messengers/DeviceStateMessageBase.cs
+++ b/src/PepperDash.Essentials.MobileControl.Messengers/Messengers/DeviceStateMessageBase.cs
@@ -8,20 +8,6 @@ namespace PepperDash.Essentials.AppServer.Messengers
   /// </summary>
   public class DeviceStateMessageBase : DeviceMessageBase
   {
-    /// <summary>
-    /// The interfaces implmented by the device sending the messsage
-    /// </summary>
-    [JsonProperty("interfaces")]
-    public List<string> Interfaces { get; private set; }
-
-    /// <summary>
-    /// Sets the interfaces implemented by the device sending the message
-    /// </summary>
-    /// <param name="interfaces"></param>
-    public void SetInterfaces(List<string> interfaces)
-    {
-      Interfaces = interfaces;
-    }
   }
 
 }
\ No newline at end of file
diff --git a/src/PepperDash.Essentials.MobileControl.Messengers/Messengers/MessengerBase.cs b/src/PepperDash.Essentials.MobileControl.Messengers/Messengers/MessengerBase.cs
index 9d22803d..fbbaa5e5 100644
--- a/src/PepperDash.Essentials.MobileControl.Messengers/Messengers/MessengerBase.cs
+++ b/src/PepperDash.Essentials.MobileControl.Messengers/Messengers/MessengerBase.cs
@@ -258,8 +258,6 @@ namespace PepperDash.Essentials.AppServer.Messengers
                     throw new ArgumentNullException("device");
                 }
 
-                message.SetInterfaces(_deviceInterfaces);
-
                 message.Key = _device.Key;
 
                 message.Name = _device.Name;
@@ -285,8 +283,6 @@ namespace PepperDash.Essentials.AppServer.Messengers
         {
             try
             {
-                deviceState.SetInterfaces(_deviceInterfaces);
-
                 deviceState.Key = _device.Key;
 
                 deviceState.Name = _device.Name;