a1629272

By: Tom Sydney Kerckhove <syd@cs-syd.eu>

Report a top-level binding in a test file beside spec

A helper in a test file is code with no test over it, in the one place
nothing else can import. Every test that calls it reads as whatever the
helper does today, so the helper drifts and takes the meaning of those
tests with it, and the failure lands on them rather than on it.

Which fix applies is the helper's to say, and the rule names all three.
One that hides what a test asserts is duplicated into each test that
uses it. One that holds real logic becomes a function in the library,
where a test can reach it. One that builds a Spec is worth keeping
whole and goes in a TestUtils module the test files import: that is
what makes a suite where adding a case adds a resource and no test
code, and it belongs somewhere it can be named and read on its own. A
let-binding is none of this rule's business, since a binding inside
spec is read with the test that uses it.

Sixty-one findings against this repository, every one of them in its
own test suite and every one of them fixed rather than suppressed: the
helpers that hid what a test asserts are now let-bindings in the spec
that uses them, and the ones that build a Spec are functions in
Hopinion.TestUtils. RuleSpec is the whole of the second kind, and is
now four meta-properties and one mapM_.