[tonyandrewmeyer]

Two how-to guides had examples that don't work exactly as described.

The Pebble health checks how-to's unit-test example raises UnboundLocalError once its assert state_out... is filled in, because layer is used before it's defined.

• The layer is now defined first, with an http section, so the CheckInfo can take its level, startup and threshold from the same place the charm does.
• failures moves out of the layer. Pebble reports it back in a CheckInfo; it isn't a check field, so it was being silently dropped.
• The example charm compared event.info to 'online', which is never true (LazyCheckInfo has no __eq__), so it now compares event.info.name.
• The second example charm, which the text says should share one handler between the two events, observed a recovered handler it never defined. It now uses a single _on_pebble_check for both.

None of the three unit-test examples in the stored state how-to ran, and each fix exposed the next problem.

• _calculate_expensive_value was never defined, and the example charm didn't observe the events it has handlers for.
• The example computed the value in start and expected to read it in install, but install always comes first, so the two handlers (and the tests) are swapped.
• The log assertion indexed ctx.juju_log[0], which is ops' own startup line, so it now looks for the charm's line anywhere in the list.
• The peer-relation charm wrote an int into the databag and wrote application data without being the leader, and the test read expensive_value where the charm wrote expensive-value.
• The peer-relation half now has its own charm class, so it works when read on its own, and its handlers cope with the relation being gone, or the value not yet written, at stop.
• The explanation page the how-to sends readers to first had an unterminated f-string in three blocks, so none of them parsed.

[dwilding]

Thanks for fixing these!