The three forms of a state read: full tree, diff, no change.
== read
a standard window Main
.b button OK
.*c text field (settable) Value: one
d menu bar
.e File
== want
Window: "Main", App: App.
0 standard window Main
	1 button OK
	2 text field (settable) Value: one
3 menu bar
	4 File

The focused UI element is 2 text field (settable) Value: one
== read
a standard window Main
.b button OK
.*c text field (settable) Value: two
d menu bar
.e File
== want
<HEADER>
~	2 text field (settable) Value: two
The focused UI element is 2 text field (settable) Value: two
== read
a standard window Main
.b button OK
.*c text field (settable) Value: two
d menu bar
.e File
== want
Nothing changed in window "Main" since the last read.
The focused UI element is 2 text field (settable) Value: two
== end
