diff --git a/HellionChat/SelfTests/ColorEditorBufferStep.cs b/HellionChat/SelfTests/ColorEditorBufferStep.cs
index d840193..db9fdd8 100644
--- a/HellionChat/SelfTests/ColorEditorBufferStep.cs
+++ b/HellionChat/SelfTests/ColorEditorBufferStep.cs
@@ -1,27 +1,67 @@
 using Dalamud.Bindings.ImGui;
 using Dalamud.Plugin.SelfTest;
+using HellionChat.Themes;
 
 namespace HellionChat.SelfTests;
 
-// Placeholder. The real working-buffer test (Cancel discards, Save
-// persists) lands once the ColorPicker component arrives in a later
-// cycle. Listed in the registry today so /xlperf shows the slot as
-// pending instead of silently missing.
 internal sealed class ColorEditorBufferStep : ISelfTestStep
 {
+    private readonly Plugin _plugin;
+
     public ColorEditorBufferStep(Plugin plugin)
     {
-        _ = plugin;
+        _plugin = plugin;
     }
 
-    public string Name => "Hellion Chat - Color editor buffer (pending)";
+    public string Name => "Hellion Chat - Color editor buffer";
 
     public SelfTestStepResult RunStep()
     {
-        ImGui.TextDisabled(
-            "Pending ColorEditor integration — placeholder selftest, no probe runs."
-        );
-        return SelfTestStepResult.Pass;
+        var registry = _plugin.ThemeRegistry;
+        var originalActive = registry.Active;
+        var fired = 0;
+        Action handler = () => fired++;
+
+        try
+        {
+            registry.OnEditingBufferChanged += handler;
+            registry.BeginEditing(originalActive);
+
+            if (registry.EditingThemeBuffer is null)
+            {
+                ImGui.Text("EditingThemeBuffer should not be null after BeginEditing");
+                return SelfTestStepResult.Fail;
+            }
+
+            var mutatedColors = registry.EditingThemeBuffer.Colors with { Primary = 0xFF112233 };
+            registry.UpdateEditingBuffer(mutatedColors);
+
+            if (fired != 1)
+            {
+                ImGui.Text($"Expected OnEditingBufferChanged once, got {fired}");
+                return SelfTestStepResult.Fail;
+            }
+
+            registry.DiscardEditingBuffer();
+
+            if (registry.EditingThemeBuffer is not null)
+            {
+                ImGui.Text("EditingThemeBuffer should be null after Discard");
+                return SelfTestStepResult.Fail;
+            }
+
+            if (registry.Active != originalActive)
+            {
+                ImGui.Text("Active theme should be unchanged after Discard");
+                return SelfTestStepResult.Fail;
+            }
+
+            return SelfTestStepResult.Pass;
+        }
+        finally
+        {
+            registry.OnEditingBufferChanged -= handler;
+        }
     }
 
     public void CleanUp() { }