This is part 1 that does the back-end:
1. New table role_allow_switch.
2. Upgrade that copies all the allows from role_allow_assign, and then drops the old CFG->allowuserswitchrolestheycantassign.
3. Old function get_assignable_roles_for_switchrole renamed to get_switchable_roles and changed to use the new table. Fixes MDL-18604 in HEAD.
4. Switch callers to use the new function name.
5. Unit tests for this new function.
6. To make those unit tests work, new switch_global_user_id and revert_global_user_id methods in UnitTestCaseUsingDatabase for toggling $USER->id.
I still need to do the editing interface under Administration ► Users ► Permissions ► Define roles. That will be done as a second commit.
I did not fix all the DB problems in search, there are too many there for me to be prepared to clean up other people's mess.
(For once, it was not me making this mistake ;-))
This is not as ambitious as the abortive FakeDBUnitTests scheme, but this one works for simple cases.
There is a new test case class UnitTestCaseUsingDatabase to inherit from. I hope it is sufficiently well documented in its PHPdocs.
* It users $CFG->unittestprefix.
* You can access that database using $this->testdb.
* That database is empty by default, you have to call create_test_table to create the ones you want, and drop_test_table to clean them up in the end. The table definitions are read from the XMLDB file.
* When you are ready to call real Moodle code that users $DB, call switch_to_test_db and then revert_to_real_db when you are done.
* If you forget to call drop_test_table or switch_to_test_db, the class will attempt to clean up after you, but will also print rude developer debug messages telling you not to be stupid.
* There is also a load_test_data method for populating a table from an array.
The is an example of its use in lib/simpletest/testunittestusingdb.php.
Instead we have a new $ACCESSLIB_PRIVATE for all caching. Regrettably, the only way to make this work in PHP (other than rewriting everything to be methods of a class rather than functions) is to make this a global variable. However $ACCESSLIB_PRIVATE should not be thought of a global, it is a private implementation detail of accesslib.php. (And there is a comment saying that.)
There is a new function accesslib_clear_all_caches_for_unit_testing(). In a unit test, you need to call this at the start of your test method, before you set up any test data, and again at the end, after you have discarded all your test data.
This new $ACCESSLIB_PRIVATE subsumes the old $ACCESS, $RDEFS and $DITRYCONTEXTS globals.
Also, I took the opportunity to refactor the (inconsistently) duplicated code for adding a context to the caches code into a cache_context function.
