SpanCaptureReporter.collect returns spans from preceding tests

[garthk]

I'm finding SpanCaptureReporter too brittle, with tests flaking out when :oc_reporter waits longer than expected and calls report/2 with spans from preceding tests after the current test calls attach/0.

Workaround:

defmodule MyApp.Module do
  use ExUnit.Case, async: false

  test "sends traces" do
    SpanCaptureReporter.attach()
    on_exit(make_ref(), &SpanCaptureReporter.detach/0)
    began_monotonic = :erlang.monotonic_time()
    
    # ... do the work ...

    spans =
    SpanCaptureReporter.collect()
    |> Enum.filter(fn span ->
        {native_time, _} = span.start_time
        native_time >= began_monotonic
    end)

    # ... check the spans ...

[garthk]

I'm having trouble solving the flip side of this problem, now: despite :application.get_env(:opencensus, :send_interval_ms, 500) returning 1 and a :timer.sleep(100) in collect/0, and running only one test, I still can't guarantee a call to report/2. What else do I need to do to ensure the reporter runs?

Update: I found I was running two reporters because I forgot about the way config merges arrays. And, I'm still having trouble ensuring report/2 gets called. Even asking for delivery and waiting in collect/0 doesn't help:

  @doc "Collect spans from your process inbox."
  @spec collect() :: list(%Span{})
  def collect do
    send(:oc_reporter, :report_spans)
    :timer.sleep(10)
    collect_span_records([]) |> Enum.map(&Span.from/1)
  end

[garthk]

Setting send_interval_ms: 100 then forcing delivery with send(:oc_reporter, :report_spans); :timer.sleep(10) works. I don’t understand why that works when the same with send_interval_ms: 1 doesn’t. That said, I'll take it working.