+These directories contain many drawing-api-specific test applications.
+
+Within each directory's CMakeLists.txt file are you will see
+definitions of tests such as the following:
+
+ add_app_test (
+ NAME "gl_default_sb"
+ TARGET gl_tri
+ ARGS -sb
+ REF default_sb.ref.txt
+ )
+
+This block specifies a test with NAME "gl_default_sb" that involves
+executing the TARGET program "gl_tri" with ARGS of "-sb". The REF
+script contains a reference trance that should result from tracing the
+given program, along with specifications for additional checks to be
+peformed.
+
+The actual execution of the test (and parsing of the REF script) is
+performed by the python program in ../app_driver.py. This driver
+program runs the application with the given arguments, performs a
+trace of the application, checks the trace against the reference
+script, and then run a "retrace" of the application (replaying the
+commands in the trace).
+
+In addition to a dump of the expected trace content, the reference
+file can contain directives to cause the driver program to perform
+additional checking. Some of the available directives are:
+
+ #image: Dump the current framebuffer image and compare against the
+ given file.
+
+ #state: Dump the current state in JSON format and compare against
+ the given file.