The feed conformance kit: the contract of spec/08 §10–§11 as checks every provider runs (spec/08 §12, D-145).

check/3 runs one of six checks against a feed and answers its findings, {check, reason} terms, [] for a feed that passes; check/2 runs them all and format/1 words a finding. use Visualize.Feed.Conformance, opts inside a module that uses ExUnit.Case writes one test per check that fails with the findings:

defmodule MyApp.FeedTest do
  use ExUnit.Case, async: true

  use Visualize.Feed.Conformance,
    feed: MyApp.Feed.new(),
    windows: [nil, [10, 20]],
    push: &MyApp.Feed.emit/1
end

The kit drives the feed through Visualize.Feed alone and calls every callback in a process of its own, so a callback that raises is a finding ({:raised, call, reason}), not a crash of the check. It references no ExUnit function itself: describe, test and flunk appear only in the code use writes into the caller's module. A callback is judged by the reductions its process spends, never by the clock, so a loaded host changes no verdict (#852, D-221).

Options

• feed: — the feed (to use: an expression, evaluated in each test).
• windows: — the windows fetched, [nil] by default; a feed naming :window needs one with a bound.
• budgets: — the budgets each window is fetched with, [nil, 5].
• push: — a function of the feed that makes it push; a feed naming :push needs one.
• down: — a feed of the same provider that cannot answer, held to error values.
• timeout: — the liveness bound: milliseconds before a callback that has not answered is hung — blocked, not slow — and the wait for a first push (30_000).
• reductions: — the most reductions one callback may spend, the feed author's cost budget; nil, the default, makes no cost claim.
• processes: — pids or registered names whose reductions during a callback count toward its budget, for a feed that does its work in a server ([]).
• quiet: — milliseconds of silence that end a push (100).
• name: — to use only: the describe block's name, "feed conformance".

Examples

iex> signal = Visualize.Signals.new(:discrete, [:t, :n], window: 3)
iex> feed = Visualize.Feed.Signals.new(signal, tick: 10)
iex> Visualize.Feed.Conformance.check(feed, windows: [nil, [2, 6]])
[]