No test verifying `Code.tag()` returns correct tags for all 603 codecs

[sumanjeet0012]

The only test for Code.tag() checks 4 codecs out of 603. There is no parametrized test that verifies every codec returns the correct tag, which is why 6 missing tags went undetected.

Problem

The current test in tests/test_code.py only covers 4 codecs:

def test_code_tag(self):
    code = Code(0x12)  # sha2-256
    assert code.tag() == "multihash"

    code = Code(0x04)  # ip4
    assert code.tag() == "multiaddr"

    code = Code(0x01)  # cidv1
    assert code.tag() == "cid"

    code = Code(0x55)  # raw
    assert code.tag() == "ipld"

This covers 4 out of 603 codecs and 4 out of 23 tags. The 6 missing tags (multikey, multisig, nonce, shelter, softhash, vlad) went undetected because no test exercises codecs from those categories.

Proposed Solution

Add a parametrized test that checks at least one codec from every tag category:

TAG_TEST_CASES = [
    # (code, expected_tag)
    (0x12, "multihash"),        # sha2-256
    (0x04, "multiaddr"),        # ip4
    (0x70, "ipld"),             # dag-pb
    (0x01, "cid"),              # cidv1
    (0x50, "serialization"),    # protobuf
    (0x30, "multiformat"),      # multicodec
    (0xE7, "key"),              # secp256k1-pub
    (0x2F, "namespace"),        # path
    (0x22, "hash"),             # murmur3-x64-64
    (0x1A14, "holochain"),      # (if applicable)
    (0x900, "transport"),       # transport-bitswap
    (0xD0E7, "varsig"),         # es256k
    (0xF101, "filecoin"),       # fil-commitment-unsealed
    (0x2000, "encryption"),     # aes-gcm-256
    (0xCE11, "zeroxcert"),      # zeroxcert-imprint-256
    (0x1100, "libp2p"),         # (if applicable)
    (0xA000, "multikey"),       # chacha20-poly1305
    (0x123B, "nonce"),          # nonce
    (0xCC01, "softhash"),       # iscc
    (0x1207, "vlad"),           # vlad
    # multisig + shelter codecs...
]

@pytest.mark.parametrize("code,expected_tag", TAG_TEST_CASES)
def test_code_tag_all_categories(code, expected_tag):
    assert Code(code).tag() == expected_tag

Additionally, add a test that verifies no codec returns "<unknown>":

def test_no_unknown_tags():
    """Every codec in CODECS should have a recognized tag."""
    for name, info in CODECS.items():
        code = Code(info["prefix"])
        assert code.tag() != "<unknown>", f"Codec {name} (0x{info['prefix']:x}) has unknown tag"

Related

• Test file: tests/test_code.py
• Function under test: _get_tag() in multicodec/code.py