diff --git a/test/test_backfill_allocator.py b/test/test_backfill_allocator.py
deleted file mode 100644
index 631fb203c..000000000
--- a/test/test_backfill_allocator.py
+++ /dev/null
@@ -1,184 +0,0 @@
-import unittest
-import logging
-import random
-
-from datetime import datetime, timedelta
-from util.migrate.allocator import CompletedKeys, NoAvailableKeysError, yield_random_entries
-
-
-class CompletedTestCase(unittest.TestCase):
-  def test_merge_blocks_operations(self):
-    candidates = CompletedKeys(10)
-    self.assertEqual(10, candidates.num_remaining)
-    candidates.mark_completed(1, 5)
-
-    self.assertTrue(candidates.is_available(5))
-    self.assertTrue(candidates.is_available(0))
-    self.assertFalse(candidates.is_available(1))
-    self.assertFalse(candidates.is_available(4))
-    self.assertFalse(candidates.is_available(11))
-    self.assertFalse(candidates.is_available(10))
-    self.assertEqual(1, len(candidates._slabs))
-    self.assertEqual(6, candidates.num_remaining)
-
-    candidates.mark_completed(5, 6)
-    self.assertFalse(candidates.is_available(5))
-    self.assertTrue(candidates.is_available(6))
-    self.assertEqual(1, len(candidates._slabs))
-    self.assertEqual(5, candidates.num_remaining)
-
-    candidates.mark_completed(3, 8)
-    self.assertTrue(candidates.is_available(9))
-    self.assertTrue(candidates.is_available(8))
-    self.assertFalse(candidates.is_available(7))
-    self.assertEqual(1, len(candidates._slabs))
-    self.assertEqual(3, candidates.num_remaining)
-
-  def test_adjust_max(self):
-    candidates = CompletedKeys(10)
-    self.assertEqual(10, candidates.num_remaining)
-    self.assertEqual(0, len(candidates._slabs))
-
-    self.assertTrue(candidates.is_available(9))
-    candidates.mark_completed(5, 12)
-    self.assertEqual(0, len(candidates._slabs))
-    self.assertEqual(5, candidates.num_remaining)
-
-    self.assertFalse(candidates.is_available(9))
-    self.assertTrue(candidates.is_available(4))
-
-  def test_adjust_min(self):
-    candidates = CompletedKeys(10)
-    self.assertEqual(10, candidates.num_remaining)
-    self.assertEqual(0, len(candidates._slabs))
-
-    self.assertTrue(candidates.is_available(2))
-    candidates.mark_completed(0, 3)
-    self.assertEqual(0, len(candidates._slabs))
-    self.assertEqual(7, candidates.num_remaining)
-
-    self.assertFalse(candidates.is_available(2))
-    self.assertTrue(candidates.is_available(4))
-
-  def test_inside_block(self):
-    candidates = CompletedKeys(10)
-    self.assertEqual(10, candidates.num_remaining)
-    candidates.mark_completed(1, 8)
-    self.assertEqual(1, len(candidates._slabs))
-    self.assertEqual(3, candidates.num_remaining)
-
-    candidates.mark_completed(2, 5)
-    self.assertEqual(1, len(candidates._slabs))
-    self.assertEqual(3, candidates.num_remaining)
-    self.assertFalse(candidates.is_available(1))
-    self.assertFalse(candidates.is_available(5))
-
-  def test_wrap_block(self):
-    candidates = CompletedKeys(10)
-    self.assertEqual(10, candidates.num_remaining)
-    candidates.mark_completed(2, 5)
-    self.assertEqual(1, len(candidates._slabs))
-    self.assertEqual(7, candidates.num_remaining)
-
-    candidates.mark_completed(1, 8)
-    self.assertEqual(1, len(candidates._slabs))
-    self.assertEqual(3, candidates.num_remaining)
-    self.assertFalse(candidates.is_available(1))
-    self.assertFalse(candidates.is_available(5))
-
-  def test_non_contiguous(self):
-    candidates = CompletedKeys(10)
-    self.assertEqual(10, candidates.num_remaining)
-
-    candidates.mark_completed(1, 5)
-    self.assertEqual(1, len(candidates._slabs))
-    self.assertEqual(6, candidates.num_remaining)
-    self.assertTrue(candidates.is_available(5))
-    self.assertTrue(candidates.is_available(6))
-
-    candidates.mark_completed(6, 8)
-    self.assertEqual(2, len(candidates._slabs))
-    self.assertEqual(4, candidates.num_remaining)
-    self.assertTrue(candidates.is_available(5))
-    self.assertFalse(candidates.is_available(6))
-
-  def test_big_merge(self):
-    candidates = CompletedKeys(10)
-    self.assertEqual(10, candidates.num_remaining)
-
-    candidates.mark_completed(1, 5)
-    self.assertEqual(1, len(candidates._slabs))
-    self.assertEqual(6, candidates.num_remaining)
-
-    candidates.mark_completed(6, 8)
-    self.assertEqual(2, len(candidates._slabs))
-    self.assertEqual(4, candidates.num_remaining)
-
-    candidates.mark_completed(5, 6)
-    self.assertEqual(1, len(candidates._slabs))
-    self.assertEqual(3, candidates.num_remaining)
-
-  def test_range_limits(self):
-    candidates = CompletedKeys(10)
-    self.assertFalse(candidates.is_available(-1))
-    self.assertFalse(candidates.is_available(10))
-
-    self.assertTrue(candidates.is_available(9))
-    self.assertTrue(candidates.is_available(0))
-
-  def test_random_saturation(self):
-    candidates = CompletedKeys(100)
-    with self.assertRaises(NoAvailableKeysError):
-      for _ in range(101):
-        start = candidates.get_block_start_index(10)
-        self.assertTrue(candidates.is_available(start))
-        candidates.mark_completed(start, start + 10)
-
-    self.assertEqual(0, candidates.num_remaining)
-
-  def test_huge_dataset(self):
-    candidates = CompletedKeys(1024 * 1024)
-    start_time = datetime.now()
-    iterations = 0
-    with self.assertRaises(NoAvailableKeysError):
-      while (datetime.now() - start_time) < timedelta(seconds=10):
-        start = candidates.get_block_start_index(1024)
-        self.assertTrue(candidates.is_available(start))
-        candidates.mark_completed(start, start + random.randint(512, 1024))
-        iterations += 1
-
-    self.assertGreater(iterations, 1024)
-    self.assertEqual(0, candidates.num_remaining)
-
-
-class FakeQuery(object):
-  def __init__(self, result_list):
-    self._result_list = result_list
-
-  def limit(self, *args, **kwargs):
-    return self
-
-  def where(self, *args, **kwargs):
-    return self
-
-  def order_by(self, *args, **kwargs):
-    return self
-
-  def __iter__(self):
-    return self._result_list.__iter__()
-
-
-class QueryAllocatorTest(unittest.TestCase):
-  FAKE_PK_FIELD = 10  # Must be able to compare to integers
-
-  def test_no_work(self):
-    def create_empty_query():
-      return FakeQuery([])
-
-    for _ in yield_random_entries(create_empty_query, self.FAKE_PK_FIELD, 1, 10):
-      self.fail('There should never be any actual work!')
-
-
-if __name__ == '__main__':
-  logging.basicConfig(level=logging.DEBUG)
-  unittest.main()
diff --git a/util/migrate/test/test_backfill_allocator.py b/util/migrate/test/test_backfill_allocator.py
new file mode 100644
index 000000000..c7a7f4f6f
--- /dev/null
+++ b/util/migrate/test/test_backfill_allocator.py
@@ -0,0 +1,176 @@
+import random
+
+import pytest
+
+from datetime import datetime, timedelta
+from util.migrate.allocator import CompletedKeys, NoAvailableKeysError, yield_random_entries
+
+def test_merge_blocks_operations():
+  candidates = CompletedKeys(10)
+  assert candidates.num_remaining == 10
+  candidates.mark_completed(1, 5)
+
+  assert candidates.is_available(5)
+  assert candidates.is_available(0)
+  assert not candidates.is_available(1)
+  assert not candidates.is_available(4)
+  assert not candidates.is_available(11)
+  assert not candidates.is_available(10)
+  assert len(candidates._slabs) == 1
+  assert candidates.num_remaining == 6
+
+  candidates.mark_completed(5, 6)
+  assert not candidates.is_available(5)
+  assert candidates.is_available(6)
+  assert len(candidates._slabs) == 1
+  assert candidates.num_remaining == 5
+
+  candidates.mark_completed(3, 8)
+  assert candidates.is_available(9)
+  assert candidates.is_available(8)
+  assert not candidates.is_available(7)
+  assert len(candidates._slabs) == 1
+  assert candidates.num_remaining == 3
+
+def test_adjust_max():
+  candidates = CompletedKeys(10)
+  assert candidates.num_remaining == 10
+  assert len(candidates._slabs) == 0
+
+  assert candidates.is_available(9)
+  candidates.mark_completed(5, 12)
+  assert len(candidates._slabs) == 0
+  assert candidates.num_remaining == 5
+
+  assert not candidates.is_available(9)
+  assert candidates.is_available(4)
+
+def test_adjust_min():
+  candidates = CompletedKeys(10)
+  assert candidates.num_remaining == 10
+  assert len(candidates._slabs) == 0
+
+  assert candidates.is_available(2)
+  candidates.mark_completed(0, 3)
+  assert len(candidates._slabs) == 0
+  assert candidates.num_remaining == 7
+
+  assert not candidates.is_available(2)
+  assert candidates.is_available(4)
+
+def test_inside_block():
+  candidates = CompletedKeys(10)
+  assert candidates.num_remaining == 10
+  candidates.mark_completed(1, 8)
+  assert len(candidates._slabs) == 1
+  assert candidates.num_remaining == 3
+
+  candidates.mark_completed(2, 5)
+  assert len(candidates._slabs) == 1
+  assert candidates.num_remaining == 3
+  assert not candidates.is_available(1)
+  assert not candidates.is_available(5)
+
+def test_wrap_block():
+  candidates = CompletedKeys(10)
+  assert candidates.num_remaining == 10
+  candidates.mark_completed(2, 5)
+  assert len(candidates._slabs) == 1
+  assert candidates.num_remaining == 7
+
+  candidates.mark_completed(1, 8)
+  assert len(candidates._slabs) == 1
+  assert candidates.num_remaining == 3
+  assert not candidates.is_available(1)
+  assert not candidates.is_available(5)
+
+def test_non_contiguous():
+  candidates = CompletedKeys(10)
+  assert candidates.num_remaining == 10
+
+  candidates.mark_completed(1, 5)
+  assert len(candidates._slabs) == 1
+  assert candidates.num_remaining == 6
+  assert candidates.is_available(5)
+  assert candidates.is_available(6)
+
+  candidates.mark_completed(6, 8)
+  assert len(candidates._slabs) == 2
+  assert candidates.num_remaining == 4
+  assert candidates.is_available(5)
+  assert not candidates.is_available(6)
+
+def test_big_merge():
+  candidates = CompletedKeys(10)
+  assert candidates.num_remaining == 10
+
+  candidates.mark_completed(1, 5)
+  assert len(candidates._slabs) == 1
+  assert candidates.num_remaining == 6
+
+  candidates.mark_completed(6, 8)
+  assert len(candidates._slabs) == 2
+  assert candidates.num_remaining == 4
+
+  candidates.mark_completed(5, 6)
+  assert len(candidates._slabs) == 1
+  assert candidates.num_remaining == 3
+
+def test_range_limits():
+  candidates = CompletedKeys(10)
+  assert not candidates.is_available(-1)
+  assert not candidates.is_available(10)
+
+  assert candidates.is_available(9)
+  assert candidates.is_available(0)
+
+def test_random_saturation():
+  candidates = CompletedKeys(100)
+  with pytest.raises(NoAvailableKeysError):
+    for _ in range(101):
+      start = candidates.get_block_start_index(10)
+      assert candidates.is_available(start)
+      candidates.mark_completed(start, start + 10)
+
+  assert candidates.num_remaining == 0
+
+def test_huge_dataset():
+  candidates = CompletedKeys(1024 * 1024)
+  start_time = datetime.now()
+  iterations = 0
+  with pytest.raises(NoAvailableKeysError):
+    while (datetime.now() - start_time) < timedelta(seconds=10):
+      start = candidates.get_block_start_index(1024)
+      assert candidates.is_available(start)
+      candidates.mark_completed(start, start + random.randint(512, 1024))
+      iterations += 1
+
+  assert iterations > 1024
+  assert candidates.num_remaining == 0
+
+
+class FakeQuery(object):
+  def __init__(self, result_list):
+    self._result_list = result_list
+
+  def limit(self, *args, **kwargs):
+    return self
+
+  def where(self, *args, **kwargs):
+    return self
+
+  def order_by(self, *args, **kwargs):
+    return self
+
+  def __iter__(self):
+    return self._result_list.__iter__()
+
+
+FAKE_PK_FIELD = 10  # Must be able to compare to integers
+
+def test_no_work():
+  def create_empty_query():
+    return FakeQuery([])
+
+  for _ in yield_random_entries(create_empty_query, FAKE_PK_FIELD, 1, 10):
+    assert False, 'There should never be any actual work!'