edge-case-sweep
Weak sweeping looks like: happy path passes, one if (!input) return added, done. Strong sweeping walks a fixed list against every new or changed code path, decides each applicable case, and proves the decision with a run.
Procedure
- List the changed entry points (functions, handlers, commands) and the inputs each receives.
- Walk the checklist below against each. For every case that can reach the code, record one of: handle (a code path exists), reject loudly (specific error, non-zero exit, 4xx — and say what the caller sees), or note (deliberately unhandled, listed in the report). Silent wrong behavior is the one unacceptable outcome.
- For every handle/reject decision, exercise it: run a test or a one-off call with that input and observe the outcome. "Handled" without an observed run is a claim, not a result.
- Do not add guards for inputs the code cannot receive; state the invariant that excludes them instead. Defensive noise hides the real checks.
Checklist
Inputs
- empty:
"",[],{}, zero rows, zero-byte file - absent: null / undefined / missing key / missing flag — distinct from empty, and the distinction must survive the whole path, not just the entry check
- boundaries: 0, -1, exactly-at-limit, limit+1, first and last element, single element
- huge: 10^6 items, multi-GB file, pathologically long string — does it stream or load everything?
- weird text: unicode, emoji, RTL, newlines in fields, quotes, leading/trailing whitespace, case variants, path separators
- duplicates and unsorted order wherever uniqueness or order is assumed
State & time
- called twice (idempotency), called concurrently, retried after partial success — is any output left half-written?
- stale state: file changed since read, record deleted between fetch and update
- timezone, DST, end-of-month/year, leap day, clock skew
Environment
- dependency down / slow / returning errors or malformed data: what does the caller see, and does it time out?
- permissions denied, disk full, network cut mid-operation
Outputs
- the reject path returns the documented type (exception class, status code, exit code), never a success-shaped value with bad contents
- partial results are impossible or clearly marked as partial
Report
List the cases you exercised and the cases you deliberately left unhandled. A stated limitation is fine; a hidden one is a bug report waiting.
