Add test for initial CRC32CHash value

Additionally, remove the empty values given to the several constructors
in the other tests, since they are the same as the default value for the
data parameter.

Signed-off-by: Rodrigo Tobar <rtobar@icrar.org>

test/test_crc32c.py

@@ -136,15 +136,24 @@ class CRCTestValue(NamedTuple):
 @pytest.mark.skipif(crc32c is None, reason="no crc32c support in this platform")
 class TestCRC32CHash:
     def test_misc(self) -> None:
-        crc32c_hash = crc32c.CRC32CHash(b"")
+        crc32c_hash = crc32c.CRC32CHash()
 
         assert crc32c_hash.digest_size == 4
         assert crc32c_hash.name == "crc32c"
         assert len(crc32c_hash.digest()) == crc32c_hash.digest_size
         assert len(crc32c_hash.hexdigest()) == crc32c_hash.digest_size * 2
 
+    def test_initial_value(self) -> None:
+        crc32c_hash = crc32c.CRC32CHash()
+        crc32c_hash.update(b"hello world")
+        expected = crc32c_hash.digest()
+
+        crc32c_hash = crc32c.CRC32CHash(b"hello")
+        crc32c_hash.update(b" world")
+        assert expected == crc32c_hash.digest()
+
     def test_copy(self) -> None:
-        crc32c_hash = crc32c.CRC32CHash(b"")
+        crc32c_hash = crc32c.CRC32CHash()
         crc32c_hash_copy = crc32c_hash.copy()
 
         assert crc32c_hash.digest() == crc32c_hash_copy.digest()
@@ -172,7 +181,7 @@ def _check_values(crc32c_hash: crc32c.CRC32CHash, crc: int) -> None:
             assert len(crc32c_hash.hexdigest()) == 8
 
         def test_piece_by_piece(self, data: bytes, crc: int) -> None:
-            crc32c_hash = crc32c.CRC32CHash(b"")
+            crc32c_hash = crc32c.CRC32CHash()
             for x in as_individual_bytes(data):
                 crc32c_hash.update(x)
             self._check_values(crc32c_hash, crc)