backend/tests/test_midi_analyzer.py

"""Tests for MIDI analyzer service."""

import pytest
from backend.services.midi_analyzer import (
    extract_bpm_from_midi,
    extract_key_from_midi,
    validate_midi_audio_sync,
)


def test_midi_bpm_extraction(sample_midi_120bpm):
    """Should extract exactly 120 BPM from MIDI."""
    result = extract_bpm_from_midi(sample_midi_120bpm)
    assert result["bpm"] == 120.0
    assert result["confidence"] == 1.0


def test_midi_key_extraction(sample_midi_120bpm):
    """C major scale MIDI should detect C major."""
    result = extract_key_from_midi(sample_midi_120bpm)
    assert result["key"] == "C"
    assert result["mode"] == "major"


def test_midi_sync_validation(sample_midi_120bpm):
    """Duration validation should work."""
    # The MIDI is short, just test the function doesn't crash
    is_synced = validate_midi_audio_sync(sample_midi_120bpm, audio_duration=8.0)
    assert isinstance(is_synced, bool)


def test_midi_bpm_returns_dict(sample_midi_120bpm):
    """BPM extraction should return properly structured dict."""
    result = extract_bpm_from_midi(sample_midi_120bpm)

    assert isinstance(result, dict)
    assert "bpm" in result
    assert "confidence" in result
    assert "tempo_changes" in result


def test_midi_key_returns_dict(sample_midi_120bpm):
    """Key extraction should return properly structured dict."""
    result = extract_key_from_midi(sample_midi_120bpm)

    assert isinstance(result, dict)
    assert "key" in result
    assert "mode" in result
    assert "confidence" in result


def test_midi_bpm_default_tempo():
    """MIDI without tempo should default to 120 BPM."""
    import mido

    mid = mido.MidiFile()
    track = mido.MidiTrack()
    mid.tracks.append(track)
    # Just add a note, no tempo message
    track.append(mido.Message('note_on', note=60, velocity=100, time=0))
    track.append(mido.Message('note_off', note=60, velocity=0, time=480))

    result = extract_bpm_from_midi(mid)
    assert result["bpm"] == 120.0