safety test

Author: ejfine

AGENTS.md

@@ -23,6 +23,7 @@ This project is a Copier template used to generate other copier templates. It is
 - Avoid magic values in comparisons in tests in all languages (like ruff rule PLR2004 specifies)
 - Prefer using random values in tests rather than arbitrary ones (e.g. the faker library, uuids, random.randint) when possible. For enums, pick randomly rather than hardcoding one value.
 - Avoid loops in tests — assert each item explicitly so failures pinpoint the exact element. When verifying a condition across all items in a collection, collect the violations into a list and assert it's empty (e.g., assert [x for x in items if bad_condition(x)] == []).
+- When a test's final assertion is an absence (e.g., element is `null`, list is empty, modal is closed), include a prior presence assertion confirming the expected state existed before the action that removed it. A test whose only assertion is an absence check can pass vacuously if setup silently failed.
 - When asserting a mock or spy was called with specific arguments, always constrain as tightly as possible. In order of preference: (1) assert called exactly once with those args (`assert_called_once_with` in Python, `toHaveBeenCalledExactlyOnceWith` in Vitest/Jest); (2) if multiple calls are expected, assert the total call count and use a positional or last-call assertion (`nthCalledWith`, `lastCalledWith` / `assert_has_calls` with `call_args_list[n]`); (3) plain "called with at any point" (`toHaveBeenCalledWith`, `assert_called_with`) is a last resort only when neither the call count nor the call order can reasonably be constrained.
 
 ### Python Testing