There is no test cases as it's not trivial to do a test case for this.
The new code for Maria is however executed by the test case in the bug report.

mysql-test/mysql-test-run.pl:
  Avoid warnings when running with --extern
storage/maria/ha_maria.cc:
  Disable not complete assert until Sanja can push a proper fix
storage/maria/ma_delete.c:
  Fix that pageflag for page is calculated based on original values
storage/maria/ma_search.c:
  Ensure that prev_length structure variable is properly reset when not used
storage/myisam/mi_search.c:
  Ensure that prev_length structure variable is properly reset when not used