The source conformance kit: the contract of spec/01 §2–§4 as checks every source runs (spec/01 §9).

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

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

  use Macaw.Data.Source.Conformance,
    source: MyApp.Source.new(),
    requests: [[], [window: [10, 20]]],
    push: &MyApp.Source.emit/1
end

The kit drives the source through Macaw.Data.Source alone and calls every callback in a process of its own (Macaw.Data.Bounded), 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, so the kit loads in production. A callback is judged by the reductions its process spends, never by the clock, so a loaded host changes no verdict.

Ported from visualize's Visualize.Feed.Conformance, with the checks a source's superset of a feed needs: a describe context, parameters, as_of, one answer per now and viewer independence.

Options

• source: the source (to use: an expression, evaluated in each test).
• context: the host's configuration for the source, passed to describe/2 (nil).
• requests: what is asked, each a keyword list of Macaw.Data.Source.Request fields among params, window, box, region, latest and as_of; [[]] by default. A source naming a capability needs a request that probes it.
• budgets: the budgets each request is fetched with, [nil, 5].
• now: the request's now, a DateTime; the moment the check starts by default.
• viewers: two opaque viewers, the first asking every request and the second held to the same answer when the source declares itself viewer independent.
• as_of: the instant an :as_of source is asked as of; a day before now by default.
• push: a function of the source that makes it push; a source naming :push needs one.
• down: a source of the same kind 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 source 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 source 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, "source conformance".

Examples

iex> Macaw.Data.Source.Conformance.check(%Macaw.Data.Test.Reference{},
...>   requests: [[], [window: [2, 6]]])
[]