headroom/tests/test_request_outcome.py

"""Tests for :class:`headroom.proxy.outcome.RequestOutcome` and the
:meth:`HeadroomProxy._record_request_outcome` funnel.

The point of this file is the *contract* — every behavioural assertion
here is a thing that, prior to the funnel, lived inline at one or more
of the 18 metrics-emit sites identified in
``docs/superpowers/specs/P0-proxy-pipeline-audit.md``. Locking the
contract in tests means future migrations onto the funnel cannot
silently regress the wire shape.
"""

from __future__ import annotations

import asyncio
import contextlib
import logging
from dataclasses import FrozenInstanceError
from typing import Any
from unittest.mock import AsyncMock, MagicMock

import pytest

from headroom.proxy.outcome import RequestOutcome

# ── Value-type contract ────────────────────────────────────────────────


def _outcome(**overrides: Any) -> RequestOutcome:
    """Construct a RequestOutcome with sensible defaults; override fields per test."""
    defaults: dict[str, Any] = {
        "request_id": "req-1",
        "provider": "anthropic",
        "model": "claude-sonnet-4",
        "original_tokens": 1000,
        "optimized_tokens": 300,
        "output_tokens": 50,
        "tokens_saved": 700,
        "attempted_input_tokens": 800,
    }
    defaults.update(overrides)
    return RequestOutcome(**defaults)


def test_outcome_is_frozen() -> None:
    """Mutability would let a handler patch the outcome after handing it
    to the funnel — bypassing the contract. Must error."""
    o = _outcome()
    with pytest.raises(FrozenInstanceError):
        o.cache_read_tokens = 999  # type: ignore[misc]


def test_cache_hit_is_derived_not_stored() -> None:
    """Pre-refactor, 9 of 18 ``RequestLog`` sites hardcoded ``cache_hit=False``
    even when ``cache_read_tokens > 0``. Deriving from the actual value
    makes "forgot to compute it" structurally impossible."""
    assert _outcome(cache_read_tokens=0).cache_hit is False
    assert _outcome(cache_read_tokens=1).cache_hit is True
    assert _outcome(cache_read_tokens=500).cache_hit is True


def test_cache_hit_pct_handles_zero_denominator() -> None:
    """No reads + no writes is a no-cache request, not a 0%-hit cache request.
    Returning 0 here is correct as long as dashboards distinguish via the
    absolute ``cache_read_tokens`` / ``cache_write_tokens`` values."""
    assert _outcome(cache_read_tokens=0, cache_write_tokens=0).cache_hit_pct == 0


def test_cache_hit_pct_rounds_to_int() -> None:
    """PERF log line consumed by ``headroom perf`` parses an integer here;
    keep the type contract tight."""
    o = _outcome(cache_read_tokens=2, cache_write_tokens=1)  # 66.66%
    assert o.cache_hit_pct == 67
    assert isinstance(o.cache_hit_pct, int)


def test_savings_pct_handles_zero_original() -> None:
    """A request with 0 original tokens — e.g. an empty body — should not
    raise ZeroDivisionError. Sites pre-refactor handled this inconsistently."""
    assert _outcome(original_tokens=0).savings_pct == 0.0


def test_savings_pct_basic() -> None:
    assert _outcome(original_tokens=1000, tokens_saved=300).savings_pct == 30.0


def test_provider_specific_fields_default_to_zero() -> None:
    """Anthropic's 5m/1h cache TTL splits don't exist on OpenAI / Gemini.
    The dataclass defaults them to 0 so non-Anthropic handlers don't
    have to know about them."""
    o = _outcome(provider="openai", cache_read_tokens=100, cache_write_tokens=200)
    assert o.cache_write_5m_tokens == 0
    assert o.cache_write_1h_tokens == 0
    # And OpenAI's "inferred" flag defaults False — only the OpenAI
    # handler sets it True after running _infer_openai_cache_write_tokens.
    assert o.cache_inferred is False


def test_optional_fields_default_to_neutral_values() -> None:
    """Handlers that don't have a field (e.g. Bedrock with no waste_signals)
    must not have to pass anything — defaults handle it."""
    o = _outcome()
    assert o.ttfb_ms == 0.0
    assert o.pipeline_timing is None
    assert o.waste_signals is None
    assert o.transforms_applied == ()
    assert o.turn_id is None
    assert o.request_messages is None
    assert o.tags == {}
    assert o.client is None  # unidentified harness


def test_client_field_round_trips() -> None:
    """The ``client`` field is the proof point that the refactor pays
    out across harnesses — one field-add gives every dashboard a
    per-harness dimension for free.
    """
    o = _outcome(client="codex")
    assert o.client == "codex"


def test_stream_outcome_derives_gemini_contents_metadata() -> None:
    outcome = RequestOutcome.from_stream(
        body={
            "systemInstruction": {"parts": [{"text": "sys"}]},
            "contents": [{"role": "user", "parts": [{"text": "hello"}]}],
        },
        provider="vertex:google",
        model="gemini-2.0-flash",
        request_id="req-gemini-stream",
        original_tokens=12,
        optimized_tokens=10,
        output_tokens=3,
        tokens_saved=2,
        transforms_applied=["compress"],
        total_latency_ms=25.0,
        overhead_ms=4.0,
        tags={"route": "vertex"},
        client="codex",
        log_full_messages=True,
    )

    assert outcome.provider == "vertex:google"
    assert outcome.num_messages == 1
    assert outcome.request_messages == [{"role": "user", "parts": [{"text": "hello"}]}]
    assert outcome.turn_id is not None


# ── classify_client — the harness ID source ─────────────────────────


def test_classify_client_recognises_known_harness_user_agents() -> None:
    from headroom.proxy.auth_mode import classify_client

    cases = [
        ({"User-Agent": "codex-cli/0.30.0 (osx)"}, "codex"),
        ({"User-Agent": "claude-code/1.4.2"}, "claude-code"),
        ({"User-Agent": "claude-cli/2.0"}, "claude-code"),  # aliased
        ({"User-Agent": "cursor/0.42.1 (electron)"}, "cursor"),
        ({"User-Agent": "aider/0.50.0"}, "aider"),
        ({"User-Agent": "zed/0.143.0"}, "zed"),
        ({"User-Agent": "opencode/1.0"}, "opencode"),
        ({"User-Agent": "github-copilot/x.y.z"}, "copilot"),
    ]
    for headers, expected in cases:
        assert classify_client(headers) == expected, headers


def test_classify_client_x_client_header_wins_over_user_agent() -> None:
    from headroom.proxy.auth_mode import classify_client

    # X-Client wins even when UA matches a different harness
    h = {"User-Agent": "codex-cli/0.30.0", "X-Client": "my-custom-harness"}
    assert classify_client(h) == "my-custom-harness"


def test_classify_client_returns_none_for_unknown_traffic() -> None:
    """``None`` is the loud "unidentified" signal — downstream consumers
    can group these as "unknown" rather than silently bucketing into
    a default that would mislead dashboards."""
    from headroom.proxy.auth_mode import classify_client

    assert classify_client({"User-Agent": "Mozilla/5.0"}) is None
    assert classify_client({}) is None
    assert classify_client({"User-Agent": ""}) is None


# ── Funnel contract (_record_request_outcome) ──────────────────────────


class _CollectingLogger:
    """Minimal stand-in for ``RequestLogger``."""

    def __init__(self) -> None:
        self.logs: list[Any] = []

    def log(self, entry: Any) -> None:
        self.logs.append(entry)


class _FunnelHarness:
    """Pulls just enough of HeadroomProxy onto an object to exercise
    ``_record_request_outcome`` without instantiating the full proxy.

    The harness assigns the real method to ``self`` via descriptor
    binding so the implementation is exactly the production one — no
    forking, no mock-the-thing-you're-testing.
    """

    def __init__(self, *, with_cost_tracker: bool = True, with_logger: bool = True) -> None:
        from headroom.proxy.server import HeadroomProxy

        self.metrics = MagicMock()
        self.metrics.record_request = AsyncMock()
        self.cost_tracker = MagicMock() if with_cost_tracker else None
        self.logger = _CollectingLogger() if with_logger else None
        # Bind the real method to this harness.
        self._record_request_outcome = HeadroomProxy._record_request_outcome.__get__(
            self, type(self)
        )


@pytest.mark.asyncio
async def test_funnel_calls_metrics_with_full_kwargs() -> None:
    """The funnel must pass EVERY field that
    ``PrometheusMetrics.record_request`` knows about, not the
    pre-refactor "pass-what-was-convenient" subset. Otherwise a handler
    that forgets to populate a field silently degrades dashboard data."""
    h = _FunnelHarness()
    o = _outcome(
        provider="openai",
        model="gpt-4",
        optimized_tokens=300,
        output_tokens=50,
        tokens_saved=700,
        attempted_input_tokens=800,
        cache_read_tokens=200,
        cache_write_tokens=100,
        cache_write_5m_tokens=50,
        cache_write_1h_tokens=50,
        uncached_input_tokens=0,
        total_latency_ms=1234.5,
        overhead_ms=12.3,
        ttfb_ms=200.0,
        pipeline_timing={"phase": 1.0},
        waste_signals={"skipped": 3},
    )
    await h._record_request_outcome(o)

    h.metrics.record_request.assert_awaited_once()
    kwargs = h.metrics.record_request.await_args.kwargs
    assert kwargs["provider"] == "openai"
    assert kwargs["model"] == "gpt-4"
    assert kwargs["input_tokens"] == 300  # optimized → input
    assert kwargs["output_tokens"] == 50
    assert kwargs["tokens_saved"] == 700
    assert kwargs["latency_ms"] == 1234.5
    assert kwargs["cached"] is True  # derived from cache_read > 0
    assert kwargs["overhead_ms"] == 12.3
    assert kwargs["ttfb_ms"] == 200.0
    assert kwargs["pipeline_timing"] == {"phase": 1.0}
    assert kwargs["waste_signals"] == {"skipped": 3}
    assert kwargs["cache_read_tokens"] == 200
    assert kwargs["cache_write_tokens"] == 100
    assert kwargs["cache_write_5m_tokens"] == 50
    assert kwargs["cache_write_1h_tokens"] == 50
    assert kwargs["uncached_input_tokens"] == 0
    assert kwargs["attempted_input_tokens"] == 800


@pytest.mark.asyncio
async def test_funnel_passes_canonical_record_tokens_shape() -> None:
    """``cost_tracker.record_tokens`` takes ``(model, tokens_saved,
    optimized_tokens)`` positionally and the cache args as kwargs. The
    funnel preserves this — moving anything to positional would break
    sites that pass kwargs explicitly."""
    h = _FunnelHarness()
    o = _outcome(
        model="claude-sonnet-4",
        optimized_tokens=300,
        tokens_saved=700,
        cache_read_tokens=200,
        cache_write_tokens=100,
        cache_write_5m_tokens=80,
        cache_write_1h_tokens=20,
        uncached_input_tokens=0,
    )
    await h._record_request_outcome(o)

    h.cost_tracker.record_tokens.assert_called_once()
    args, kwargs = h.cost_tracker.record_tokens.call_args
    assert args == ("claude-sonnet-4", 700, 300)
    assert kwargs == {
        "cache_read_tokens": 200,
        "cache_write_tokens": 100,
        "cache_write_5m_tokens": 80,
        "cache_write_1h_tokens": 20,
        "uncached_tokens": 0,
        "output_tokens": 50,
    }


@pytest.mark.asyncio
async def test_funnel_skips_cost_tracker_when_absent() -> None:
    """When the proxy was started with ``--no-cost``, ``cost_tracker``
    is None and the funnel must skip step 2 silently."""
    h = _FunnelHarness(with_cost_tracker=False)
    await h._record_request_outcome(_outcome())
    # No crash, metrics still recorded.
    h.metrics.record_request.assert_awaited_once()


@pytest.mark.asyncio
async def test_funnel_logs_request_with_derived_cache_hit() -> None:
    """The RequestLog row needs cache_hit derived from cache_read>0, not
    the hardcoded False that 9 of 18 pre-refactor sites used."""
    h = _FunnelHarness()
    await h._record_request_outcome(_outcome(cache_read_tokens=200, cache_write_tokens=100))
    assert len(h.logger.logs) == 1
    log_entry = h.logger.logs[0]
    assert log_entry.cache_hit is True


@pytest.mark.asyncio
async def test_funnel_skips_request_log_when_logger_absent() -> None:
    """Same pattern as cost_tracker — optional surface."""
    h = _FunnelHarness(with_logger=False)
    await h._record_request_outcome(_outcome())
    h.metrics.record_request.assert_awaited_once()  # still happens


@pytest.mark.asyncio
async def test_funnel_tail_survives_cancellation_inside_record_request() -> None:
    """A client disconnect must not tear per-request bookkeeping in half.

    Four call sites are ``finally:`` blocks inside streaming async generators
    (``streaming.py:1611``, ``:1859``, ``:2069``, ``openai.py:8614``), and
    ``record_request`` suspends partway through — it awaits the savings-ledger
    append in a worker thread after the Prometheus counters have already been
    committed. A cancellation landing on that await used to skip every effect
    below it, leaving the request counted in Prometheus but absent from the cost
    tracker, the request log, and the PERF line ``headroom perf`` reads.

    Without the ``asyncio.shield`` in ``_record_request_outcome`` the release
    below never resumes the funnel and this test times out on ``logged``.
    """
    h = _FunnelHarness()

    logged = asyncio.Event()
    collect = h.logger.log

    def log_and_signal(entry: Any) -> None:
        collect(entry)
        logged.set()

    h.logger.log = log_and_signal  # type: ignore[method-assign]

    entered = asyncio.Event()
    release = asyncio.Event()

    async def suspending_record_request(**kwargs: Any) -> None:
        # Stands in for the `await asyncio.to_thread(...)` ledger append: the
        # counters are in, and the funnel is now parked on an await.
        entered.set()
        await release.wait()

    h.metrics.record_request = suspending_record_request

    task = asyncio.create_task(h._record_request_outcome(_outcome()))
    await asyncio.wait_for(entered.wait(), timeout=5)

    task.cancel()
    # The shield deliberately does not swallow the cancellation — the caller
    # still sees CancelledError, so generator teardown propagates unchanged.
    with contextlib.suppress(asyncio.CancelledError):
        await task

    release.set()
    await asyncio.wait_for(logged.wait(), timeout=5)

    assert h.cost_tracker.record_tokens.called, "cost tracker was skipped by the cancellation"
    assert len(h.logger.logs) == 1, "request log was skipped by the cancellation"


@pytest.mark.asyncio
async def test_funnel_emits_perf_log_with_canonical_shape(
    caplog: pytest.LogCaptureFixture,
) -> None:
    """``headroom perf`` parses this exact ``key=value`` format. Changing
    it breaks the analyzer. The contract: model, msgs, tok_before,
    tok_after, tok_saved, cache_read, cache_write, cache_hit_pct,
    opt_ms, transforms — in that order, space-separated."""
    h = _FunnelHarness()
    # Direct handler attach: caplog otherwise drops propagation-disabled
    # records (the proxy disables ``headroom.*`` propagation once started).
    target = logging.getLogger("headroom.proxy")
    captured: list[logging.LogRecord] = []

    class _H(logging.Handler):
        def emit(self, record: logging.LogRecord) -> None:
            captured.append(record)

    handler = _H(level=logging.INFO)
    target.addHandler(handler)
    prior_level = target.level
    target.setLevel(logging.INFO)
    try:
        await h._record_request_outcome(
            _outcome(
                request_id="req-perf",
                model="gpt-4",
                original_tokens=1000,
                optimized_tokens=300,
                tokens_saved=700,
                cache_read_tokens=200,
                cache_write_tokens=100,
                num_messages=5,
                overhead_ms=12.0,
                transforms_applied=("smart_crusher", "content_router"),
            )
        )
    finally:
        target.removeHandler(handler)
        target.setLevel(prior_level)

    perf_lines = [r.getMessage() for r in captured if " PERF " in r.getMessage()]
    assert len(perf_lines) == 1
    line = perf_lines[0]
    assert "[req-perf] PERF " in line
    assert "model=gpt-4" in line
    assert "msgs=5" in line
    assert "tok_before=1000" in line
    assert "tok_after=300" in line
    assert "tok_saved=700" in line
    assert "cache_read=200" in line
    assert "cache_write=100" in line
    assert "cache_hit_pct=67" in line  # 200/(200+100) * 100 = 67
    assert "opt_ms=12" in line


# ── Funnel: per-client analytics surface ─────────────────────────────


@pytest.mark.asyncio
async def test_funnel_appends_client_to_perf_log_when_set() -> None:
    """``headroom perf --client X`` filtering relies on the ``client=X``
    token at the end of the PERF line. Absent client means no token —
    the PERF line stays clean for unidentified traffic."""
    h = _FunnelHarness()
    target = logging.getLogger("headroom.proxy")
    captured: list[logging.LogRecord] = []

    class _H(logging.Handler):
        def emit(self, record: logging.LogRecord) -> None:
            captured.append(record)

    handler = _H(level=logging.INFO)
    target.addHandler(handler)
    prior_level = target.level
    target.setLevel(logging.INFO)
    try:
        await h._record_request_outcome(_outcome(client="codex"))
    finally:
        target.removeHandler(handler)
        target.setLevel(prior_level)

    perf_lines = [r.getMessage() for r in captured if " PERF " in r.getMessage()]
    assert len(perf_lines) == 1
    assert "client=codex" in perf_lines[0]


@pytest.mark.asyncio
async def test_funnel_omits_client_from_perf_log_when_unidentified() -> None:
    """When ``client`` is None the PERF line must NOT include a
    bogus ``client=`` token — that would mislead the parser into
    bucketing unidentified traffic as the empty string."""
    h = _FunnelHarness()
    target = logging.getLogger("headroom.proxy")
    captured: list[logging.LogRecord] = []

    class _H(logging.Handler):
        def emit(self, record: logging.LogRecord) -> None:
            captured.append(record)

    handler = _H(level=logging.INFO)
    target.addHandler(handler)
    prior_level = target.level
    target.setLevel(logging.INFO)
    try:
        await h._record_request_outcome(_outcome(client=None))
    finally:
        target.removeHandler(handler)
        target.setLevel(prior_level)

    perf_lines = [r.getMessage() for r in captured if " PERF " in r.getMessage()]
    assert len(perf_lines) == 1
    assert "client=" not in perf_lines[0]


@pytest.mark.asyncio
async def test_funnel_stamps_client_into_request_log_tags() -> None:
    """Dashboards already filter on RequestLog.tags. Copying ``client``
    into tags gives per-harness slicing for free with no new column."""
    h = _FunnelHarness()
    await h._record_request_outcome(_outcome(client="aider"))
    assert len(h.logger.logs) == 1
    assert h.logger.logs[0].tags.get("client") == "aider"


# ── from_stream classmethod (streaming-finalizer construction shape) ──
#
# Three streaming finalizers (``_finalize_stream_response``,
# ``_stream_response_bedrock``, ``_stream_openai_via_backend``) each used
# to construct ``RequestOutcome(...)`` inline with the same body- and
# config-derived fields — ``attempted_input_tokens``, ``num_messages``,
# ``request_messages``, ``turn_id``, tuple-conversion of
# ``transforms_applied``, ``tags`` normalization. One site (Bedrock)
# computed ``turn_id``; the other two silently dropped it — a real bug
# the helper fixes by computing it uniformly. ``from_stream`` is the
# canonical construction point so the three finalizers cannot drift
# apart on derivation logic again.


def _stream_kwargs(**overrides: Any) -> dict[str, Any]:
    """Minimal kwargs for ``RequestOutcome.from_stream``; override per test."""
    base: dict[str, Any] = {
        "body": {"messages": [{"role": "user", "content": "hi"}]},
        "provider": "anthropic",
        "model": "claude-sonnet-4",
        "request_id": "req-1",
        "original_tokens": 1000,
        "optimized_tokens": 300,
        "output_tokens": 50,
        "tokens_saved": 700,
        "transforms_applied": ["smart_crusher"],
        "total_latency_ms": 1234.5,
        "overhead_ms": 12.3,
        "tags": {"a": "b"},
        "client": "codex",
        "log_full_messages": False,
    }
    base.update(overrides)
    return base


def test_from_stream_returns_request_outcome() -> None:
    o = RequestOutcome.from_stream(**_stream_kwargs())
    assert isinstance(o, RequestOutcome)


def test_from_stream_derives_attempted_input_tokens_from_optimized_plus_saved() -> None:
    """One of the six derivations the three finalizers each computed
    inline. Centralising it makes the dashboard's active-savings
    denominator structurally consistent across providers (#454/#455)."""
    o = RequestOutcome.from_stream(**_stream_kwargs(optimized_tokens=300, tokens_saved=700))
    assert o.attempted_input_tokens == 1000


def test_from_stream_counts_messages_from_body() -> None:
    """``num_messages`` powers PERF ``msgs=N``. Computing it from the
    body in one place prevents the historical drift where some sites
    used ``original_messages`` and others used ``body["messages"]``."""
    body = {"messages": [{"role": "user", "content": "1"}, {"role": "user", "content": "2"}]}
    assert RequestOutcome.from_stream(**_stream_kwargs(body=body)).num_messages == 2


def test_from_stream_handles_missing_messages_key() -> None:
    """Empty body — e.g. a probe request — must yield num_messages=0,
    not raise KeyError. All three pre-refactor sites used
    ``len(body.get("messages", []))`` so the contract is already
    "default to 0"."""
    assert RequestOutcome.from_stream(**_stream_kwargs(body={})).num_messages == 0


def test_from_stream_always_computes_turn_id() -> None:
    """The bug the helper is fixing: pre-refactor, only the Bedrock
    finalizer called ``compute_turn_id``. Sites 1 and 3 silently dropped
    it, breaking the dashboard's multi-turn-session grouping for every
    Anthropic-SSE and OpenAI-via-backend request. The helper computes
    it uniformly."""
    body = {
        "messages": [{"role": "user", "content": "hi"}],
        "system": "you are helpful",
    }
    o = RequestOutcome.from_stream(**_stream_kwargs(body=body, model="claude-sonnet-4"))
    assert o.turn_id is not None
    assert isinstance(o.turn_id, str)
    # Stable: same body+model produces the same turn_id.
    o2 = RequestOutcome.from_stream(**_stream_kwargs(body=body, model="claude-sonnet-4"))
    assert o.turn_id == o2.turn_id


def test_from_stream_converts_transforms_to_tuple() -> None:
    """``transforms_applied`` is typed as ``tuple[str, ...]`` on the
    dataclass (frozen → must be hashable/immutable). Callers pass lists.
    The helper does the conversion so no caller has to remember."""
    o = RequestOutcome.from_stream(**_stream_kwargs(transforms_applied=["a", "b"]))
    assert o.transforms_applied == ("a", "b")
    assert isinstance(o.transforms_applied, tuple)


def test_from_stream_normalises_none_tags_to_empty_dict() -> None:
    """``tags=None`` is the common case (no routing tags); the dataclass
    contract is ``dict[str, str]``. Pre-refactor each site wrote
    ``tags or {}``; the helper does it once."""
    assert RequestOutcome.from_stream(**_stream_kwargs(tags=None)).tags == {}


def test_from_stream_omits_request_messages_when_log_full_messages_disabled() -> None:
    """``log_full_messages=False`` is the default; message bodies are
    sensitive (tool outputs, secrets) and must not land in the request
    log unless explicitly enabled."""
    body = {"messages": [{"role": "user", "content": "secret"}]}
    o = RequestOutcome.from_stream(**_stream_kwargs(body=body, log_full_messages=False))
    assert o.request_messages is None


def test_from_stream_includes_request_messages_when_log_full_messages_enabled() -> None:
    """Same path, opt-in for full-message logging — used by
    /transformations/feed when the operator enables it."""
    body = {"messages": [{"role": "user", "content": "hi"}]}
    o = RequestOutcome.from_stream(**_stream_kwargs(body=body, log_full_messages=True))
    assert o.request_messages == body["messages"]


def test_from_stream_threads_provider_specific_cache_fields() -> None:
    """Anthropic populates all five cache fields; OpenAI-via-backend
    sets ``cache_inferred=True``; Gemini populates read only. The
    helper must pass each through without forcing every caller to
    pass every field."""
    o = RequestOutcome.from_stream(
        **_stream_kwargs(),
        cache_read_tokens=100,
        cache_write_tokens=200,
        cache_write_5m_tokens=150,
        cache_write_1h_tokens=50,
        uncached_input_tokens=10,
    )
    assert o.cache_read_tokens == 100
    assert o.cache_write_tokens == 200
    assert o.cache_write_5m_tokens == 150
    assert o.cache_write_1h_tokens == 50
    assert o.uncached_input_tokens == 10
    assert o.cache_inferred is False  # default — only set True by OpenAI sites


def test_from_stream_threads_waste_signals_for_openai_via_backend_site() -> None:
    """Only the OpenAI-via-backend finalizer populates ``waste_signals``;
    the helper threads it through as an optional kwarg."""
    o = RequestOutcome.from_stream(
        **_stream_kwargs(),
        waste_signals={"skipped_units": 3, "applied_units": 7},
    )
    assert o.waste_signals == {"skipped_units": 3, "applied_units": 7}