tests/test_midi.py

"""Tests for midi.py — MIDI event utilities."""

import io

import mido
import pytest

from midi import events_to_midbytes, validate_event


# ---------------------------------------------------------------------------
# validate_event
# ---------------------------------------------------------------------------

class TestValidateEvent:
    def test_valid_event(self):
        assert validate_event(
            {"type": "note_on", "note": 60, "velocity": 100, "time": 0.0}
        )

    def test_missing_type(self):
        assert not validate_event({"note": 60, "velocity": 100, "time": 0.0})

    def test_missing_note(self):
        assert not validate_event({"type": "note_on", "velocity": 100, "time": 0.0})

    def test_missing_velocity(self):
        assert not validate_event({"type": "note_on", "note": 60, "time": 0.0})

    def test_missing_time(self):
        assert not validate_event({"type": "note_on", "note": 60, "velocity": 100})

    def test_empty_dict(self):
        assert not validate_event({})


# ---------------------------------------------------------------------------
# events_to_midbytes
# ---------------------------------------------------------------------------

class TestEventsToMidbytes:
    def test_returns_valid_midi_bytes(self, single_note_events):
        mid_bytes = events_to_midbytes(single_note_events)
        assert isinstance(mid_bytes, bytes)
        assert len(mid_bytes) > 0
        # Should start with MThd header.
        assert mid_bytes[:4] == b"MThd"

    def test_round_trip_note_count(self, c_major_chord_events):
        """The exported MIDI file should contain the same number of note messages."""
        mid_bytes = events_to_midbytes(c_major_chord_events)
        mid = mido.MidiFile(file=io.BytesIO(mid_bytes))
        messages = [msg for msg in mid.tracks[0] if msg.type in ("note_on", "note_off")]
        assert len(messages) == len(c_major_chord_events)

    def test_preserves_note_values(self, melody_events):
        mid_bytes = events_to_midbytes(melody_events)
        mid = mido.MidiFile(file=io.BytesIO(mid_bytes))
        note_ons = [msg.note for msg in mid.tracks[0] if msg.type == "note_on"]
        expected = [e["note"] for e in melody_events if e["type"] == "note_on"]
        assert note_ons == expected

    def test_empty_events(self):
        mid_bytes = events_to_midbytes([])
        assert isinstance(mid_bytes, bytes)
        # Should still be a valid MIDI file (header + empty track).
        assert mid_bytes[:4] == b"MThd"

    def test_custom_tempo(self, single_note_events):
        mid_bytes = events_to_midbytes(single_note_events, tempo_bpm=60)
        mid = mido.MidiFile(file=io.BytesIO(mid_bytes))
        tempo_msgs = [msg for msg in mid.tracks[0] if msg.type == "set_tempo"]
        assert len(tempo_msgs) == 1
        assert mido.tempo2bpm(tempo_msgs[0].tempo) == pytest.approx(60, abs=0.01)

    def test_skips_malformed_events(self):
        events = [
            {"type": "note_on", "note": 60, "velocity": 100, "time": 0.0},
            {"bad": "event"},  # no type/note/time
            {"type": "note_off", "note": 60, "velocity": 0, "time": 0.5},
        ]
        mid_bytes = events_to_midbytes(events)
        mid = mido.MidiFile(file=io.BytesIO(mid_bytes))
        messages = [msg for msg in mid.tracks[0] if msg.type in ("note_on", "note_off")]
        assert len(messages) == 2