DevTools 

DevTools - Development tools for UI authors.

A relatively simple AddOn which provides some slash commands

/reload

Just a shortcut (since I'm lazy) for /script ReloadUI()

/dump expression

Prints the result of executing a Lua expression (Basically /script but with
output). It should be able to handle pretty much any kind of return data
(including self-referential nested tables!)

e.g.
/dump GetPlayerMapPosition("player")

DevTools: value=GetPlayerMapPosition("player")
[1]0.43320921063423
[2]0.69365233182907

/dtchatevent

Toggle chat event tracking/debugging (this is a saved setting). When
active each chat frame message (in all standard ChatFrames) will be
prefixed by a marker that can be clicked on the pop up the details of
the event that created it.

/dtchatevent buffer

Displays the current chat event rolling buffer size.

/dtchatevent buffer <size>

Set the current chat event rolling buffer size
(e.g. /dtchatevent buffer 10000), the default buffer size is 1000.

/dtframestack

Toggles the 'frame stack' window, which displays the stack of visible
frames under the mouse pointer. (There are also key bindings for this).

/dteventtrace [command]
/dtevents [command]

Without any command it toggles visibility of the event trace frame. The
following commands are also recognized:

stop -- Halts collection of events
start -- Starts normal collection of events
fill -- Starts collection of 50 events (then stops)
toggle -- Equivalent to no parameters