1FOO = foo
 2FOO_SPACE_BAR:=foo bar
 3FOO_COMMA_BAR:=foo,bar
 4$(FOO_SPACE_BAR):=foo
 5$(FOO_COMMA_BAR):=foo
 6FOOREF := FOO
 7
 8test:
 9	echo $(origin FOO)
10	echo $(origin FOO BAR)
11	echo $(origin FOO,BAR)
12	echo $(origin UNDEFINED)
13	echo $(origin PATH)
14	echo $(origin MAKEFILE_LIST)
15	echo $(origin CC)
16	echo $(origin $(FOOREF))
17
18# TODO: support environment override, command line, and override.
19# TODO: Also add more tests especially for += and ?=
20