Issue #16686: Fixed a lot of bugs in audioop module.

* avgpp() and maxpp() no more crash on empty and 1-samples input fragment. They now work when peak-peak values are greater INT_MAX.
* ratecv() no more crashes on empty input fragment.
* Fixed an integer overflow in ratecv().
* Fixed an integer overflow in add() and bias() for 32-bit samples.
* reverse(), lin2lin() and ratecv() no more lose precision for 32-bit samples.
* max() and rms() no more returns negative result for 32-bit sample -0x80000000.
* minmax() now returns correct max value for 32-bit sample -0x80000000.
* avg(), mul(), tomono() and tostereo() now round negative result down and can return 32-bit sample -0x80000000.
* add() now can return 32-bit sample -0x80000000.

1 files changed, 272 insertions, 127 deletions

diff --git a/Lib/test/test_audioop.py b/Lib/test/test_audioop.py
index c14e8b8..ff67f2c 100644
--- a/Lib/test/test_audioop.py
+++ b/Lib/test/test_audioop.py
@@ -1,25 +1,21 @@
 import audioop
+import sys
 import unittest
 from test.support import run_unittest
 
-endian = 'big' if audioop.getsample(b'\0\1', 2, 0) == 1 else 'little'
+def pack(width, data):
+    return b''.join(v.to_bytes(width, sys.byteorder, signed=True) for v in data)
 
-def gendata1():
-    return b'\0\1\2'
+packs = {w: (lambda *data, width=w: pack(width, data)) for w in (1, 2, 4)}
+maxvalues = {w: (1 << (8 * w - 1)) - 1 for w in (1, 2, 4)}
+minvalues = {w: -1 << (8 * w - 1) for w in (1, 2, 4)}
 
-def gendata2():
-    if endian == 'big':
-        return b'\0\0\0\1\0\2'
-    else:
-        return b'\0\0\1\0\2\0'
-
-def gendata4():
-    if endian == 'big':
-        return b'\0\0\0\0\0\0\0\1\0\0\0\2'
-    else:
-        return b'\0\0\0\0\1\0\0\0\2\0\0\0'
-
-data = [gendata1(), gendata2(), gendata4()]
+datas = {
+    1: b'\x00\x12\x45\xbb\x7f\x80\xff',
+    2: packs[2](0, 0x1234, 0x4567, -0x4567, 0x7fff, -0x8000, -1),
+    4: packs[4](0, 0x12345678, 0x456789ab, -0x456789ab,
+                0x7fffffff, -0x80000000, -1),
+}
 
 INVALID_DATA = [
     (b'abc', 0),
@@ -31,171 +27,320 @@ INVALID_DATA = [
 class TestAudioop(unittest.TestCase):
 
     def test_max(self):
-        self.assertEqual(audioop.max(data[0], 1), 2)
-        self.assertEqual(audioop.max(data[1], 2), 2)
-        self.assertEqual(audioop.max(data[2], 4), 2)
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.max(b'', w), 0)
+            p = packs[w]
+            self.assertEqual(audioop.max(p(5), w), 5)
+            self.assertEqual(audioop.max(p(5, -8, -1), w), 8)
+            self.assertEqual(audioop.max(p(maxvalues[w]), w), maxvalues[w])
+            self.assertEqual(audioop.max(p(minvalues[w]), w), -minvalues[w])
+            self.assertEqual(audioop.max(datas[w], w), -minvalues[w])
 
     def test_minmax(self):
-        self.assertEqual(audioop.minmax(data[0], 1), (0, 2))
-        self.assertEqual(audioop.minmax(data[1], 2), (0, 2))
-        self.assertEqual(audioop.minmax(data[2], 4), (0, 2))
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.minmax(b'', w),
+                             (0x7fffffff, -0x80000000))
+            p = packs[w]
+            self.assertEqual(audioop.minmax(p(5), w), (5, 5))
+            self.assertEqual(audioop.minmax(p(5, -8, -1), w), (-8, 5))
+            self.assertEqual(audioop.minmax(p(maxvalues[w]), w),
+                             (maxvalues[w], maxvalues[w]))
+            self.assertEqual(audioop.minmax(p(minvalues[w]), w),
+                             (minvalues[w], minvalues[w]))
+            self.assertEqual(audioop.minmax(datas[w], w),
+                             (minvalues[w], maxvalues[w]))
 
     def test_maxpp(self):
-        self.assertEqual(audioop.maxpp(data[0], 1), 0)
-        self.assertEqual(audioop.maxpp(data[1], 2), 0)
-        self.assertEqual(audioop.maxpp(data[2], 4), 0)
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.maxpp(b'', w), 0)
+            self.assertEqual(audioop.maxpp(packs[w](*range(100)), w), 0)
+            self.assertEqual(audioop.maxpp(packs[w](9, 10, 5, 5, 0, 1), w), 10)
+            self.assertEqual(audioop.maxpp(datas[w], w),
+                             maxvalues[w] - minvalues[w])
 
     def test_avg(self):
-        self.assertEqual(audioop.avg(data[0], 1), 1)
-        self.assertEqual(audioop.avg(data[1], 2), 1)
-        self.assertEqual(audioop.avg(data[2], 4), 1)
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.avg(b'', w), 0)
+            p = packs[w]
+            self.assertEqual(audioop.avg(p(5), w), 5)
+            self .assertEqual(audioop.avg(p(5, 8), w), 6)
+            self.assertEqual(audioop.avg(p(5, -8), w), -2)
+            self.assertEqual(audioop.avg(p(maxvalues[w], maxvalues[w]), w),
+                             maxvalues[w])
+            self.assertEqual(audioop.avg(p(minvalues[w], minvalues[w]), w),
+                             minvalues[w])
+        self.assertEqual(audioop.avg(packs[4](0x50000000, 0x70000000), 4),
+                         0x60000000)
+        self.assertEqual(audioop.avg(packs[4](-0x50000000, -0x70000000), 4),
+                         -0x60000000)
 
     def test_avgpp(self):
-        self.assertEqual(audioop.avgpp(data[0], 1), 0)
-        self.assertEqual(audioop.avgpp(data[1], 2), 0)
-        self.assertEqual(audioop.avgpp(data[2], 4), 0)
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.avgpp(b'', w), 0)
+            self.assertEqual(audioop.avgpp(packs[w](*range(100)), w), 0)
+            self.assertEqual(audioop.avgpp(packs[w](9, 10, 5, 5, 0, 1), w), 10)
+        self.assertEqual(audioop.avgpp(datas[1], 1), 196)
+        self.assertEqual(audioop.avgpp(datas[2], 2), 50534)
+        self.assertEqual(audioop.avgpp(datas[4], 4), 3311897002)
 
     def test_rms(self):
-        self.assertEqual(audioop.rms(data[0], 1), 1)
-        self.assertEqual(audioop.rms(data[1], 2), 1)
-        self.assertEqual(audioop.rms(data[2], 4), 1)
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.rms(b'', w), 0)
+            p = packs[w]
+            self.assertEqual(audioop.rms(p(*range(100)), w), 57)
+            self.assertAlmostEqual(audioop.rms(p(maxvalues[w]) * 5, w),
+                                   maxvalues[w], delta=1)
+            self.assertAlmostEqual(audioop.rms(p(minvalues[w]) * 5, w),
+                                   -minvalues[w], delta=1)
+        self.assertEqual(audioop.rms(datas[1], 1), 77)
+        self.assertEqual(audioop.rms(datas[2], 2), 20001)
+        self.assertEqual(audioop.rms(datas[4], 4), 1310854152)
 
     def test_cross(self):
-        self.assertEqual(audioop.cross(data[0], 1), 0)
-        self.assertEqual(audioop.cross(data[1], 2), 0)
-        self.assertEqual(audioop.cross(data[2], 4), 0)
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.cross(b'', w), -1)
+            p = packs[w]
+            self.assertEqual(audioop.cross(p(0, 1, 2), w), 0)
+            self.assertEqual(audioop.cross(p(1, 2, -3, -4), w), 1)
+            self.assertEqual(audioop.cross(p(-1, -2, 3, 4), w), 1)
+            self.assertEqual(audioop.cross(p(0, minvalues[w]), w), 1)
+            self.assertEqual(audioop.cross(p(minvalues[w], maxvalues[w]), w), 1)
 
     def test_add(self):
-        data2 = []
-        for d in data:
-            str = bytearray(len(d))
-            for i,b in enumerate(d):
-                str[i] = 2*b
-            data2.append(str)
-        self.assertEqual(audioop.add(data[0], data[0], 1), data2[0])
-        self.assertEqual(audioop.add(data[1], data[1], 2), data2[1])
-        self.assertEqual(audioop.add(data[2], data[2], 4), data2[2])
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.add(b'', b'', w), b'')
+            self.assertEqual(audioop.add(datas[w], b'\0' * len(datas[w]), w),
+                             datas[w])
+        self.assertEqual(audioop.add(datas[1], datas[1], 1),
+                         b'\x00\x24\x7f\x80\x7f\x80\xfe')
+        self.assertEqual(audioop.add(datas[2], datas[2], 2),
+                packs[2](0, 0x2468, 0x7fff, -0x8000, 0x7fff, -0x8000, -2))
+        self.assertEqual(audioop.add(datas[4], datas[4], 4),
+                packs[4](0, 0x2468acf0, 0x7fffffff, -0x80000000,
+                       0x7fffffff, -0x80000000, -2))
 
     def test_bias(self):
-        # Note: this test assumes that avg() works
-        d1 = audioop.bias(data[0], 1, 100)
-        d2 = audioop.bias(data[1], 2, 100)
-        d4 = audioop.bias(data[2], 4, 100)
-        self.assertEqual(audioop.avg(d1, 1), 101)
-        self.assertEqual(audioop.avg(d2, 2), 101)
-        self.assertEqual(audioop.avg(d4, 4), 101)
+        for w in 1, 2, 4:
+            for bias in 0, 1, -1, 127, -128, 0x7fffffff, -0x80000000:
+                self.assertEqual(audioop.bias(b'', w, bias), b'')
+        self.assertEqual(audioop.bias(datas[1], 1, 1),
+                         b'\x01\x13\x46\xbc\x80\x81\x00')
+        self.assertEqual(audioop.bias(datas[1], 1, -1),
+                         b'\xff\x11\x44\xba\x7e\x7f\xfe')
+        self.assertEqual(audioop.bias(datas[1], 1, 0x7fffffff),
+                         b'\xff\x11\x44\xba\x7e\x7f\xfe')
+        self.assertEqual(audioop.bias(datas[1], 1, -0x80000000),
+                         datas[1])
+        self.assertEqual(audioop.bias(datas[2], 2, 1),
+                packs[2](1, 0x1235, 0x4568, -0x4566, -0x8000, -0x7fff, 0))
+        self.assertEqual(audioop.bias(datas[2], 2, -1),
+                packs[2](-1, 0x1233, 0x4566, -0x4568, 0x7ffe, 0x7fff, -2))
+        self.assertEqual(audioop.bias(datas[2], 2, 0x7fffffff),
+                packs[2](-1, 0x1233, 0x4566, -0x4568, 0x7ffe, 0x7fff, -2))
+        self.assertEqual(audioop.bias(datas[2], 2, -0x80000000),
+                datas[2])
+        self.assertEqual(audioop.bias(datas[4], 4, 1),
+                packs[4](1, 0x12345679, 0x456789ac, -0x456789aa,
+                         -0x80000000, -0x7fffffff, 0))
+        self.assertEqual(audioop.bias(datas[4], 4, -1),
+                packs[4](-1, 0x12345677, 0x456789aa, -0x456789ac,
+                         0x7ffffffe, 0x7fffffff, -2))
+        self.assertEqual(audioop.bias(datas[4], 4, 0x7fffffff),
+                packs[4](0x7fffffff, -0x6dcba989, -0x3a987656, 0x3a987654,
+                         -2, -1, 0x7ffffffe))
+        self.assertEqual(audioop.bias(datas[4], 4, -0x80000000),
+                packs[4](-0x80000000, -0x6dcba988, -0x3a987655, 0x3a987655,
+                         -1, 0, 0x7fffffff))
 
     def test_lin2lin(self):
-        # too simple: we test only the size
-        for d1 in data:
-            for d2 in data:
-                got = len(d1)//3
-                wtd = len(d2)//3
-                self.assertEqual(len(audioop.lin2lin(d1, got, wtd)), len(d2))
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.lin2lin(datas[w], w, w), datas[w])
+
+        self.assertEqual(audioop.lin2lin(datas[1], 1, 2),
+            packs[2](0, 0x1200, 0x4500, -0x4500, 0x7f00, -0x8000, -0x100))
+        self.assertEqual(audioop.lin2lin(datas[1], 1, 4),
+            packs[4](0, 0x12000000, 0x45000000, -0x45000000,
+                     0x7f000000, -0x80000000, -0x1000000))
+        self.assertEqual(audioop.lin2lin(datas[2], 2, 1),
+            b'\x00\x12\x45\xba\x7f\x80\xff')
+        self.assertEqual(audioop.lin2lin(datas[2], 2, 4),
+            packs[4](0, 0x12340000, 0x45670000, -0x45670000,
+                     0x7fff0000, -0x80000000, -0x10000))
+        self.assertEqual(audioop.lin2lin(datas[4], 4, 1),
+            b'\x00\x12\x45\xba\x7f\x80\xff')
+        self.assertEqual(audioop.lin2lin(datas[4], 4, 2),
+            packs[2](0, 0x1234, 0x4567, -0x4568, 0x7fff, -0x8000, -1))
 
     def test_adpcm2lin(self):
+        self.assertEqual(audioop.adpcm2lin(b'\x07\x7f\x7f', 1, None),
+                         (b'\x00\x00\x00\xff\x00\xff', (-179, 40)))
+        self.assertEqual(audioop.adpcm2lin(b'\x07\x7f\x7f', 2, None),
+                         (packs[2](0, 0xb, 0x29, -0x16, 0x72, -0xb3), (-179, 40)))
+        self.assertEqual(audioop.adpcm2lin(b'\x07\x7f\x7f', 4, None),
+                         (packs[4](0, 0xb0000, 0x290000, -0x160000, 0x720000,
+                                   -0xb30000), (-179, 40)))
+
         # Very cursory test
-        self.assertEqual(audioop.adpcm2lin(b'\0\0', 1, None), (b'\0' * 4, (0,0)))
-        self.assertEqual(audioop.adpcm2lin(b'\0\0', 2, None), (b'\0' * 8, (0,0)))
-        self.assertEqual(audioop.adpcm2lin(b'\0\0', 4, None), (b'\0' * 16, (0,0)))
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.adpcm2lin(b'\0' * 5, w, None),
+                             (b'\0' * w * 10, (0, 0)))
 
     def test_lin2adpcm(self):
+        self.assertEqual(audioop.lin2adpcm(datas[1], 1, None),
+                         (b'\x07\x7f\x7f', (-221, 39)))
+        self.assertEqual(audioop.lin2adpcm(datas[2], 2, None),
+                         (b'\x07\x7f\x7f', (31, 39)))
+        self.assertEqual(audioop.lin2adpcm(datas[4], 4, None),
+                         (b'\x07\x7f\x7f', (31, 39)))
+
         # Very cursory test
-        self.assertEqual(audioop.lin2adpcm(b'\0\0\0\0', 1, None), (b'\0\0', (0,0)))
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.lin2adpcm(b'\0' * w * 10, w, None),
+                             (b'\0' * 5, (0, 0)))
 
     def test_lin2alaw(self):
-        self.assertEqual(audioop.lin2alaw(data[0], 1), b'\xd5\xc5\xf5')
-        self.assertEqual(audioop.lin2alaw(data[1], 2), b'\xd5\xd5\xd5')
-        self.assertEqual(audioop.lin2alaw(data[2], 4), b'\xd5\xd5\xd5')
+        self.assertEqual(audioop.lin2alaw(datas[1], 1),
+                         b'\xd5\x87\xa4\x24\xaa\x2a\x5a')
+        self.assertEqual(audioop.lin2alaw(datas[2], 2),
+                         b'\xd5\x87\xa4\x24\xaa\x2a\x55')
+        self.assertEqual(audioop.lin2alaw(datas[4], 4),
+                         b'\xd5\x87\xa4\x24\xaa\x2a\x55')
 
     def test_alaw2lin(self):
-        # Cursory
-        d = audioop.lin2alaw(data[0], 1)
-        self.assertEqual(audioop.alaw2lin(d, 1), data[0])
-        if endian == 'big':
-            self.assertEqual(audioop.alaw2lin(d, 2),
-                             b'\x00\x08\x01\x08\x02\x10')
-            self.assertEqual(audioop.alaw2lin(d, 4),
-                             b'\x00\x08\x00\x00\x01\x08\x00\x00\x02\x10\x00\x00')
-        else:
-            self.assertEqual(audioop.alaw2lin(d, 2),
-                             b'\x08\x00\x08\x01\x10\x02')
-            self.assertEqual(audioop.alaw2lin(d, 4),
-                             b'\x00\x00\x08\x00\x00\x00\x08\x01\x00\x00\x10\x02')
+        encoded = b'\x00\x03\x24\x2a\x51\x54\x55\x58\x6b\x71\x7f'\
+                  b'\x80\x83\xa4\xaa\xd1\xd4\xd5\xd8\xeb\xf1\xff'
+        src = [-688, -720, -2240, -4032, -9, -3, -1, -27, -244, -82, -106,
+               688, 720, 2240, 4032, 9, 3, 1, 27, 244, 82, 106]
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.alaw2lin(encoded, w),
+                             packs[w](*(x << (w * 8) >> 13 for x in src)))
+
+        encoded = bytes(range(256))
+        for w in 2, 4:
+            decoded = audioop.alaw2lin(encoded, w)
+            self.assertEqual(audioop.lin2alaw(decoded, w), encoded)
 
     def test_lin2ulaw(self):
-        self.assertEqual(audioop.lin2ulaw(data[0], 1), b'\xff\xe7\xdb')
-        self.assertEqual(audioop.lin2ulaw(data[1], 2), b'\xff\xff\xff')
-        self.assertEqual(audioop.lin2ulaw(data[2], 4), b'\xff\xff\xff')
+        self.assertEqual(audioop.lin2ulaw(datas[1], 1),
+                         b'\xff\xad\x8e\x0e\x80\x00\x67')
+        self.assertEqual(audioop.lin2ulaw(datas[2], 2),
+                         b'\xff\xad\x8e\x0e\x80\x00\x7e')
+        self.assertEqual(audioop.lin2ulaw(datas[4], 4),
+                         b'\xff\xad\x8e\x0e\x80\x00\x7e')
 
     def test_ulaw2lin(self):
-        # Cursory
-        d = audioop.lin2ulaw(data[0], 1)
-        self.assertEqual(audioop.ulaw2lin(d, 1), data[0])
-        if endian == 'big':
-            self.assertEqual(audioop.ulaw2lin(d, 2),
-                             b'\x00\x00\x01\x04\x02\x0c')
-            self.assertEqual(audioop.ulaw2lin(d, 4),
-                             b'\x00\x00\x00\x00\x01\x04\x00\x00\x02\x0c\x00\x00')
-        else:
-            self.assertEqual(audioop.ulaw2lin(d, 2),
-                             b'\x00\x00\x04\x01\x0c\x02')
-            self.assertEqual(audioop.ulaw2lin(d, 4),
-                             b'\x00\x00\x00\x00\x00\x00\x04\x01\x00\x00\x0c\x02')
+        encoded = b'\x00\x0e\x28\x3f\x57\x6a\x76\x7c\x7e\x7f'\
+                  b'\x80\x8e\xa8\xbf\xd7\xea\xf6\xfc\xfe\xff'
+        src = [-8031, -4447, -1471, -495, -163, -53, -18, -6, -2, 0,
+               8031, 4447, 1471, 495, 163, 53, 18, 6, 2, 0]
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.ulaw2lin(encoded, w),
+                             packs[w](*(x << (w * 8) >> 14 for x in src)))
+
+        # Current u-law implementation has two codes fo 0: 0x7f and 0xff.
+        encoded = bytes(range(127)) + bytes(range(128, 256))
+        for w in 2, 4:
+            decoded = audioop.ulaw2lin(encoded, w)
+            self.assertEqual(audioop.lin2ulaw(decoded, w), encoded)
 
     def test_mul(self):
-        data2 = []
-        for d in data:
-            str = bytearray(len(d))
-            for i,b in enumerate(d):
-                str[i] = 2*b
-            data2.append(str)
-        self.assertEqual(audioop.mul(data[0], 1, 2), data2[0])
-        self.assertEqual(audioop.mul(data[1],2, 2), data2[1])
-        self.assertEqual(audioop.mul(data[2], 4, 2), data2[2])
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.mul(b'', w, 2), b'')
+            self.assertEqual(audioop.mul(datas[w], w, 0),
+                             b'\0' * len(datas[w]))
+            self.assertEqual(audioop.mul(datas[w], w, 1),
+                             datas[w])
+        self.assertEqual(audioop.mul(datas[1], 1, 2),
+                         b'\x00\x24\x7f\x80\x7f\x80\xfe')
+        self.assertEqual(audioop.mul(datas[2], 2, 2),
+                packs[2](0, 0x2468, 0x7fff, -0x8000, 0x7fff, -0x8000, -2))
+        self.assertEqual(audioop.mul(datas[4], 4, 2),
+                packs[4](0, 0x2468acf0, 0x7fffffff, -0x80000000,
+                         0x7fffffff, -0x80000000, -2))
 
     def test_ratecv(self):
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.ratecv(b'', w, 1, 8000, 8000, None),
+                             (b'', (-1, ((0, 0),))))
+            self.assertEqual(audioop.ratecv(b'', w, 5, 8000, 8000, None),
+                             (b'', (-1, ((0, 0),) * 5)))
+            self.assertEqual(audioop.ratecv(b'', w, 1, 8000, 16000, None),
+                             (b'', (-2, ((0, 0),))))
+            self.assertEqual(audioop.ratecv(datas[w], w, 1, 8000, 8000, None)[0],
+                             datas[w])
         state = None
-        d1, state = audioop.ratecv(data[0], 1, 1, 8000, 16000, state)
-        d2, state = audioop.ratecv(data[0], 1, 1, 8000, 16000, state)
+        d1, state = audioop.ratecv(b'\x00\x01\x02', 1, 1, 8000, 16000, state)
+        d2, state = audioop.ratecv(b'\x00\x01\x02', 1, 1, 8000, 16000, state)
         self.assertEqual(d1 + d2, b'\000\000\001\001\002\001\000\000\001\001\002')
 
+        for w in 1, 2, 4:
+            d0, state0 = audioop.ratecv(datas[w], w, 1, 8000, 16000, None)
+            d, state = b'', None
+            for i in range(0, len(datas[w]), w):
+                d1, state = audioop.ratecv(datas[w][i:i + w], w, 1,
+                                           8000, 16000, state)
+                d += d1
+            self.assertEqual(d, d0)
+            self.assertEqual(state, state0)
+
     def test_reverse(self):
-        self.assertEqual(audioop.reverse(data[0], 1), b'\2\1\0')
+        for w in 1, 2, 4:
+            self.assertEqual(audioop.reverse(b'', w), b'')
+            self.assertEqual(audioop.reverse(packs[w](0, 1, 2), w),
+                             packs[w](2, 1, 0))
 
     def test_tomono(self):
-        data2 = bytearray()
-        for d in data[0]:
-            data2.append(d)
-            data2.append(d)
-        self.assertEqual(audioop.tomono(data2, 1, 0.5, 0.5), data[0])
+        for w in 1, 2, 4:
+            data1 = datas[w]
+            data2 = bytearray(2 * len(data1))
+            for k in range(w):
+                data2[k::2*w] = data1[k::w]
+            self.assertEqual(audioop.tomono(data2, w, 1, 0), data1)
+            self.assertEqual(audioop.tomono(data2, w, 0, 1), b'\0' * len(data1))
+            for k in range(w):
+                data2[k+w::2*w] = data1[k::w]
+            self.assertEqual(audioop.tomono(data2, w, 0.5, 0.5), data1)
 
     def test_tostereo(self):
-        data2 = bytearray()
-        for d in data[0]:
-            data2.append(d)
-            data2.append(d)
-        self.assertEqual(audioop.tostereo(data[0], 1, 1, 1), data2)
+        for w in 1, 2, 4:
+            data1 = datas[w]
+            data2 = bytearray(2 * len(data1))
+            for k in range(w):
+                data2[k::2*w] = data1[k::w]
+            self.assertEqual(audioop.tostereo(data1, w, 1, 0), data2)
+            self.assertEqual(audioop.tostereo(data1, w, 0, 0), b'\0' * len(data2))
+            for k in range(w):
+                data2[k+w::2*w] = data1[k::w]
+            self.assertEqual(audioop.tostereo(data1, w, 1, 1), data2)
 
     def test_findfactor(self):
-        self.assertEqual(audioop.findfactor(data[1], data[1]), 1.0)
+        self.assertEqual(audioop.findfactor(datas[2], datas[2]), 1.0)
+        self.assertEqual(audioop.findfactor(b'\0' * len(datas[2]), datas[2]),
+                         0.0)
 
     def test_findfit(self):
-        self.assertEqual(audioop.findfit(data[1], data[1]), (0, 1.0))
+        self.assertEqual(audioop.findfit(datas[2], datas[2]), (0, 1.0))
+        self.assertEqual(audioop.findfit(datas[2], packs[2](1, 2, 0)),
+                         (1, 8038.8))
+        self.assertEqual(audioop.findfit(datas[2][:-2] * 5 + datas[2], datas[2]),
+                         (30, 1.0))
 
     def test_findmax(self):
-        self.assertEqual(audioop.findmax(data[1], 1), 2)
+        self.assertEqual(audioop.findmax(datas[2], 1), 5)
 
     def test_getsample(self):
-        for i in range(3):
-            self.assertEqual(audioop.getsample(data[0], 1, i), i)
-            self.assertEqual(audioop.getsample(data[1], 2, i), i)
-            self.assertEqual(audioop.getsample(data[2], 4, i), i)
+        for w in 1, 2, 4:
+            data = packs[w](0, 1, -1, maxvalues[w], minvalues[w])
+            self.assertEqual(audioop.getsample(data, w, 0), 0)
+            self.assertEqual(audioop.getsample(data, w, 1), 1)
+            self.assertEqual(audioop.getsample(data, w, 2), -1)
+            self.assertEqual(audioop.getsample(data, w, 3), maxvalues[w])
+            self.assertEqual(audioop.getsample(data, w, 4), minvalues[w])
 
     def test_negativelen(self):
         # from issue 3306, previously it segfaulted
         self.assertRaises(audioop.error,
-            audioop.findmax, ''.join(chr(x) for x in range(256)), -2392392)
+            audioop.findmax, bytes(range(256)), -2392392)
 
     def test_issue7673(self):
         state = None
@@ -222,9 +367,9 @@ class TestAudioop(unittest.TestCase):
             self.assertRaises(audioop.error, audioop.lin2adpcm, data, size, state)
 
     def test_wrongsize(self):
-        data = b'abc'
+        data = b'abcdefgh'
         state = None
-        for size in (-1, 3, 5):
+        for size in (-1, 0, 3, 5, 1024):
             self.assertRaises(audioop.error, audioop.ulaw2lin, data, size)
             self.assertRaises(audioop.error, audioop.alaw2lin, data, size)
             self.assertRaises(audioop.error, audioop.adpcm2lin, data, size, state)