Can't get Custom Inspector to appear (C#)

Problem: I can’t get a simple Custom Inspector to display at all the way I expect.

Here’s my very-bare-bones editor extension:
using UnityEngine;
using UnityEditor;
using System.Collections;

[CustomEditor(typeof(AIController))]
public class AIControllerEditor : Editor
{

	public override void OnInspectorGUI()
	{
		EditorGUILayout.TextArea("TEST-TEST");
	}
}

AIController extends from MonoBehaviour and is a script I can add to objects. What am I not understanding in my assumption that when I add an AIController component to a game object, I should see in its inspector window a simple text field?

All I currently get is the default inspector fields (public variables of the AIController object - ints thrown in for test purposes)

Still trying to figure out how to close my own question now…

The problem was that my Inspector pane was set to “Debug” instead of “Normal”. Brilliant.