test: group priority

Test for the group priority feature. When configuring different groups,
they should overwrite each other based on their priority.

The examples are based on [1]

[1] OCP Panel Indicator Specification_rev1.0.pdf

Change-Id: I91b96d9dc9307afb1a2abbde6278862045a28355
Signed-off-by: Alexander Hansen <alexander.hansen@9elements.com>
diff --git a/test/meson.build b/test/meson.build
index 300e977..ae1b8e6 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -27,6 +27,7 @@
 tests = [
   'utest.cpp',
   'utest-led-json.cpp',
+  'utest-group-priority.cpp',
 ]
 if get_option('persistent-led-asserted').allowed()
   test_sources += [