It would be nice to be able to write tests for the Drupal installer.
Of course with the testbot we test the installer all the time, but that is one one specific scenario: a browser-based installation with a particular install profile and a particular set of options chosen (e.g., no language imports).
Due towe can now install Drupal via an API so it should be possible to write tests which exercise this API and at the same time make sure that various installation options work correctly.
As far as I can tell, this wouldn't even be that hard (famous last words)... the only limitation is that SimpleTest needs to install on an existing site but with a different database prefix, so we may need some small changes to the API to make sure that it allows that (while still preserving security).
PASSED: [[SimpleTest]]: [MySQL] 54,433 pass(es).
PASSED: [[SimpleTest]]: [MySQL] 54,078 pass(es).
FAILED: [[SimpleTest]]: [MySQL] 54,044 pass(es), 0 fail(s), and 1 exception(s).
FAILED: [[SimpleTest]]: [MySQL] 54,147 pass(es), 1 fail(s), and 2 exception(s).