#1 Add a simple chromagram test with a plain sine.

It should produce one strong bin.

tests/reassignment_test.py

@@ -1,9 +1,43 @@
 import numpy as np
 
-from tfr.reassignment import shifted_amplitude_pair
-
+from tfr.analysis import split_to_blocks
+from tfr.spectrogram import create_window
+from tfr.reassignment import chromagram, shifted_amplitude_pair
+from tfr.tuning import pitch_to_freq
 
 def test_shifted_amplitude_pair():
     actual = shifted_amplitude_pair(np.array([[1, 2, 3]]))
     assert np.allclose(actual[0], np.array([0, 1, 2]))
     assert np.allclose(actual[1], np.array([1, 2, 3]))
+
+def test_chromagram_on_single_tone_should_have_peak_at_that_tone():
+    pitch = 12 + 7 # G5
+    f = pitch_to_freq(pitch)
+    fs = 44100
+    x = sine(sample_time(0, 1, fs=fs), freq=f)
+    block_size = 4096
+    window = create_window(block_size)
+    x_blocks, x_times = split_to_blocks(x, block_size=block_size, hop_size=2048, fs=fs)
+    bin_range = [-48, 67]
+    x_chromagram = chromagram(x_blocks, window, fs=fs, to_log=True, bin_range=bin_range, bin_division=1)
+
+    max_bin_expected = pitch - bin_range[0]
+    max_bin_actual = x_chromagram.mean(axis=0).argmax()
+
+    assert x_chromagram.shape == (22, 115)
+    assert max_bin_actual == max_bin_expected
+
+
+def sample_time(since, until, fs=44100.):
+    '''
+    Generates time sample in given interval [since; until]
+    with given sampling rate (fs).
+    '''
+    return np.arange(since, until, 1. / fs)
+
+def sine(t, freq=1., amplitude=1., phase=0.):
+    '''
+    Samples the sine function given the time samples t,
+    frequency (Hz), amplitude and phase [0; 2 * np.pi).
+    '''
+    return amplitude * np.sin(2 * np.pi * freq * t + phase)