tests/test_brain.py

"""Temperature wiring for LocalBrain — verified WITHOUT a model load.

`LocalBrain._sampler_kwargs` is a pure staticmethod and brain.py imports torch
only inside `LocalBrain.__init__`/`_generate`, so this runs at zero GPU / no torch.
"""

from __future__ import annotations

from game.brain import LocalBrain


def test_defaults_come_from_bakeoff_when_env_unset():
    # DEFAULT_* read MODEL_ID / LOCALBRAIN_TEMPERATURE at import; unset here.
    # Values are the 2026-06 bake-off picks (see the comment block in brain.py).
    assert LocalBrain.DEFAULT_MODEL == "Qwen/Qwen2.5-14B-Instruct"
    assert LocalBrain.DEFAULT_TEMPERATURE == 0.9


def test_modal_default_temperature_matches_local():
    # Both brains read the same env knob; their fallbacks must not drift apart.
    from game.brain import ModalBrain

    assert ModalBrain.DEFAULT_TEMPERATURE == LocalBrain.DEFAULT_TEMPERATURE


def test_sampler_kwargs_greedy_at_zero_and_below():
    # temperature 0 must be GREEDY (do_sample=False, no temperature passed) —
    # transformers misbehaves if you sample at temperature 0.
    assert LocalBrain._sampler_kwargs(0.0) == {"do_sample": False}
    assert LocalBrain._sampler_kwargs(-1.0) == {"do_sample": False}
    assert "temperature" not in LocalBrain._sampler_kwargs(0.0)


def test_sampler_kwargs_samples_when_warm():
    k = LocalBrain._sampler_kwargs(0.7)
    assert k["do_sample"] is True
    assert k["temperature"] == 0.7
    assert k["top_p"] == 0.9


def test_brain_import_does_not_pull_torch():
    # Importing the module (and referencing LocalBrain) must not import torch —
    # the SPEC §6 lazy-import discipline the temperature change must preserve.
    import sys

    assert "torch" not in sys.modules