old_contents: import unittest
  
  from block import Block
  
  
  class TestBlock(unittest.TestCase):
      class MerkleTreeMock:
          pass
  
      def test_init(self):
          prev = 0x123123
          tree = TestBlock.MerkleTreeMock()
          time = 0x432432
          bits = 0x1a44b9f2
  
          b = Block(prev, tree, time, bits)
  
          self.assertEqual(b.previous_block_hash, prev)
          self.assertEqual(b.version, Block.VERSION)
          self.assertEqual(b.merkle_tree, tree)
          self.assertEqual(b.time, time)
          self.assertEqual(b.difficulty, bits)
  
new_contents: import unittest
  
  from block import Block
  
  
  class TestBlock(unittest.TestCase):
      class MerkleTreeMock:
          pass
  
      def test_init(self):
          prev = bytes([123] * 32)
          tree = TestBlock.MerkleTreeMock()
          time = 432432
          bits = 0x1a44b9f2
  
          b = Block(prev, tree, time, bits)
  
          self.assertEqual(b.previous_block_hash, prev)
          self.assertEqual(b.version, Block.VERSION)
          self.assertEqual(b.merkle_tree, tree)
          self.assertEqual(b.time, time)
          self.assertEqual(b.difficulty, bits)
  
subject: Change block init test to pass bytes for hash