2.17.0: new unit testing API, and Secret fixes

What's Changed

This release adds a state-transition testing API for unit tests, formerly known as Scenario (many thanks to @PietroPasotti for his work developing and maintaining the library). Harness is still available, but we encourage all charmers to use the new API for unit tests going forward. The API is an optional install, for example: pip install ops[testing], so that the test API code does not get bundled into the charms. All of the classes that you would previously find when using ops-scenario in the scenario namespace can then be found in ops.testing. For example:

from ops import testing

ctx = testing.Context(MyCharm)
state = ctx.run(ctx.on.start(), testing.State(leader=True))
assert state.unit_status == testing.ActiveStatus()

There are also two improvements to Juju Secrets: firstly, the .id of a Secret will always include the model UUID, so it can be reliably used for cross-model relations. A more significant change is that, previously, if a charm called set_contents() and set_info() in the same hook (even if not the same event handler, or in a deferred event handler) only the last call would have any effect. This is now changed so that the calls accumulate - you can set both content and metadata in the same hook, and also if you set_contents() twice the contents will be combined. The Juju team intend to make this the secret-set behaviour in the future as well.

Additionally, ops.main is now type hinted correctly and will no longer require a type: ignore directive from users!

Features

• Optionally install Scenario with ops[testing] and expose the names in ops.testing in #1381
• Change ops.main() so that you don't need to type: ignore it in #1345
• Expand the secret ID out to the full URI when only given the ID in #1358
• Add a JujuVersion property for Pebble log forwarding to Loki in #1370
• Pre-emptively raise InvalidStatusError instead of waiting for Juju:
  • Make it an error to call CollectStatusEvent.add_status with error or unknown in #1386
  • Document and validate settable status values in _ModelBackend.set_status in #1354

Fixes

• Fix type of StatusBase subclasses by calling StatusBase.register in __init_subclass__ in #1383
• Secret.set_info and Secret.set_content can be called in the same hook in #1373

Documentation

• Add top-level intro and module-level intros in #1320
• Update the links to the Pebble docs in #1362
• Note about repeatedly setting secret value in Juju 3.6 in #1366
• config-changed is triggered by Juju trust in #1357
• Typo on CharmBase inheritance example by @theofpa in #1349
• Docs: move Pebble to a separate page in #1392

Continuous Integration

• Periodically run the unit tests of all GitHub-hosted published charms in #1365
• Update the TIOBE reporting for the changes in coverage calculation in #1367
• Spell-check the code as part of linting in #1388
• Run the smoke tests on a schedule in #1387

Testing

• Fix tests that leaked environment variables in #1385

Refactoring

• Move the content of ops.testing to ops._private.harness in #1369
• Keep the unittest.mock names in the 'mock' namespace in #1379
• Deprecate StatusBase.register decorator in #1384

Chores

• Note Juju version on legacy workaround in #1355
• Re-enable test now that Pebble directory permissions are fixed in #1363
• Generate warnings for events that will be removed in Juju 4.0 in #1374

New Contributors

• @theofpa made their first contribution in #1349

Full Changelog: 2.16.1...2.17.0