pw_unit_test: Add comment to unit test

Change-Id: I967eb7329e5691725711f82c7f7a206dcd292243
diff --git a/pw_unit_test/framework_test.cc b/pw_unit_test/framework_test.cc
index 2b16b37..2d570ee 100644
--- a/pw_unit_test/framework_test.cc
+++ b/pw_unit_test/framework_test.cc
@@ -67,9 +67,11 @@
   ASSERT_STRNE("yes", no);
 }
 
-TEST(PigweedTest, ExpectSucceedFail) {
+TEST(PigweedTest, SucceedAndFailMacros) {
   SUCCEED();
 
+  // The ADD_FAILURE() and FAIL() macros cause a test to fail if they are
+  // reached. Use them, but don't let them run so that this test still passes.
   if (false) {
     ADD_FAILURE();
     FAIL();