diff --git a/Lib/test/test_bz2.py b/Lib/test/test_bz2.py
index 030d564fc59..78b95d88faa 100644
--- a/Lib/test/test_bz2.py
+++ b/Lib/test/test_bz2.py
@@ -710,7 +710,7 @@ class BZ2DecompressorTest(BaseTest):
     def testDecompress4G(self, size):
         # "Test BZ2Decompressor.decompress() with >4GiB input"
         blocksize = 10 * 1024 * 1024
-        block = random.getrandbits(blocksize * 8).to_bytes(blocksize, 'little')
+        block = random.randbytes(blocksize)
         try:
             data = block * (size // blocksize + 1)
             compressed = bz2.compress(data)
diff --git a/Lib/test/test_lzma.py b/Lib/test/test_lzma.py
index f24ed3ca3d4..0f3af27efa9 100644
--- a/Lib/test/test_lzma.py
+++ b/Lib/test/test_lzma.py
@@ -350,7 +350,7 @@ class CompressorDecompressorTestCase(unittest.TestCase):
     def test_decompressor_bigmem(self, size):
         lzd = LZMADecompressor()
         blocksize = 10 * 1024 * 1024
-        block = random.getrandbits(blocksize * 8).to_bytes(blocksize, "little")
+        block = random.randbytes(blocksize)
         try:
             input = block * (size // blocksize + 1)
             cdata = lzma.compress(input)
diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py
index cae96802ded..99196f60431 100644
--- a/Lib/test/test_tarfile.py
+++ b/Lib/test/test_tarfile.py
@@ -386,7 +386,7 @@ class CommonReadTest(ReadTest):
     def test_ignore_zeros(self):
         # Test TarFile's ignore_zeros option.
         # generate 512 pseudorandom bytes
-        data = Random(0).getrandbits(512*8).to_bytes(512, 'big')
+        data = Random(0).randbytes(512)
         for char in (b'\0', b'a'):
             # Test if EOFHeaderError ('\0') and InvalidHeaderError ('a')
             # are ignored correctly.
diff --git a/Lib/test/test_zipfile.py b/Lib/test/test_zipfile.py
index 643c5b477ba..29d98c8092d 100644
--- a/Lib/test/test_zipfile.py
+++ b/Lib/test/test_zipfile.py
@@ -16,7 +16,7 @@ import zipfile
 
 
 from tempfile import TemporaryFile
-from random import randint, random, getrandbits
+from random import randint, random, randbytes
 
 from test.support import script_helper
 from test.support import (TESTFN, findfile, unlink, rmtree, temp_dir, temp_cwd,
@@ -33,9 +33,6 @@ SMALL_TEST_DATA = [('_ziptest1', '1q2w3e4r5t'),
                    ('ziptest2dir/ziptest3dir/_ziptest3', 'azsxdcfvgb'),
                    ('ziptest2dir/ziptest3dir/ziptest4dir/_ziptest3', '6y7u8i9o0p')]
 
-def getrandbytes(size):
-    return getrandbits(8 * size).to_bytes(size, 'little')
-
 def get_files(test):
     yield TESTFN2
     with TemporaryFile() as f:
@@ -324,7 +321,7 @@ class AbstractTestsWithSourceFile:
         # than requested.
         for test_size in (1, 4095, 4096, 4097, 16384):
             file_size = test_size + 1
-            junk = getrandbytes(file_size)
+            junk = randbytes(file_size)
             with zipfile.ZipFile(io.BytesIO(), "w", self.compression) as zipf:
                 zipf.writestr('foo', junk)
                 with zipf.open('foo', 'r') as fp:
@@ -2423,8 +2420,8 @@ class UnseekableTests(unittest.TestCase):
 class TestsWithMultipleOpens(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
-        cls.data1 = b'111' + getrandbytes(10000)
-        cls.data2 = b'222' + getrandbytes(10000)
+        cls.data1 = b'111' + randbytes(10000)
+        cls.data2 = b'222' + randbytes(10000)
 
     def make_test_archive(self, f):
         # Create the ZIP archive
diff --git a/Lib/test/test_zlib.py b/Lib/test/test_zlib.py
index f828b4c737a..02509cdf553 100644
--- a/Lib/test/test_zlib.py
+++ b/Lib/test/test_zlib.py
@@ -134,8 +134,7 @@ class BaseCompressTestCase(object):
         # Generate 10 MiB worth of random, and expand it by repeating it.
         # The assumption is that zlib's memory is not big enough to exploit
         # such spread out redundancy.
-        data = b''.join([random.getrandbits(8 * _1M).to_bytes(_1M, 'little')
-                        for i in range(10)])
+        data = random.randbytes(_1M * 10)
         data = data * (size // len(data) + 1)
         try:
             compress_func(data)
@@ -488,7 +487,7 @@ class CompressObjectTestCase(BaseCompressTestCase, unittest.TestCase):
                 # others might simply have a single RNG
                 gen = random
         gen.seed(1)
-        data = genblock(1, 17 * 1024, generator=gen)
+        data = gen.randbytes(17 * 1024)
 
         # compress, sync-flush, and decompress
         first = co.compress(data)
@@ -825,20 +824,6 @@ class CompressObjectTestCase(BaseCompressTestCase, unittest.TestCase):
         self.assertEqual(dco.decompress(gzip), HAMLET_SCENE)
 
 
-def genblock(seed, length, step=1024, generator=random):
-    """length-byte stream of random data from a seed (in step-byte blocks)."""
-    if seed is not None:
-        generator.seed(seed)
-    randint = generator.randint
-    if length < step or step < 2:
-        step = length
-    blocks = bytes()
-    for i in range(0, length, step):
-        blocks += bytes(randint(0, 255) for x in range(step))
-    return blocks
-
-
-
 def choose_lines(source, number, seed=None, generator=random):
     """Return a list of number lines randomly chosen from the source"""
     if seed is not None:
@@ -847,7 +832,6 @@ def choose_lines(source, number, seed=None, generator=random):
     return [generator.choice(sources) for n in range(number)]
 
 
-
 HAMLET_SCENE = b"""
 LAERTES