Cover andThen's applied form with an explicit Nothing - #35
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andThen was the one curryable combinator whose applied form was not tested against an absent value — the arity trap ADR-0003 closes, where Nothing IS undefined and a two-argument call must apply rather than hand back the Mapper. Drops the test asserting andThen is map by reference: it pins an implementation detail rather than behaviour, and the behavioural tests cover what callers rely on. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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Follow-up from an audit of the curryable combinators' test coverage.
Every curryable combinator has runtime tests for both the curried and applied forms, and all but one pin the arity trap ADR-0003 closes —
Nothingisundefined, so a two-argument call must apply rather than return the Mapper.maybe/andThenwas the exception: its applied form was only tested with a present value.andThen(fn, nothing<number>())produces Nothing.expect(andThen).toBe(map). It asserts andThen is map by reference — an implementation detail, not behaviour a caller depends on. The alias relationship stays documented in the docblock, and the behavioural tests cover what actually matters.🤖 Generated with Claude Code