Question: So I moved some X programs down to the mac, and I'm getting

```
Error: XTEST extension unavailable on '(null)'.

```

from xdotool.

* Does OS X X11 come with XTEST?
* If not, is there a way to add it?

Answer: 
Run the following command in the Terminal:

```
defaults write org.x.X11 enable_test_extensions -boolean true

```

(as per [here](http://xquartz.macosforge.org/trac/wiki/X112.3.2)). Then quit and restart the X server; the XTEST extension should then be available.
For XQuartz,

```
defaults write org.macosforge.xquartz.X11 enable_test_extensions -bool yes

```

See [this link](https://xquartz.macosforge.org/trac/ticket/414).