No benchmark tests for `sum()`, `encode()`, `decode()` operations

There are no benchmark tests. go-multihash includes BenchmarkSum, BenchmarkEncode, BenchmarkDecode, BenchmarkBlake2B, and BenchmarkSumAllLarge which help catch performance regressions.

Problem

The test suite has functional tests but zero benchmarks. Operations like Blake2b hashing (which has 64 variants) and SHAKE variable-length hashing have no performance baseline.

Proposed Solution

1. Install pytest-benchmark as a dev dependency.

2. Create tests/test_benchmarks.py:

   import pytest
   from multihash import sum, encode, decode, Func
   
   BENCH_DATA = b"benchmark test data for multihash operations" * 100
   
   @pytest.mark.benchmark
   def test_bench_sum_sha256(benchmark):
       benchmark(sum, BENCH_DATA, Func.sha2_256)
   
   @pytest.mark.benchmark
   def test_bench_sum_sha512(benchmark):
       benchmark(sum, BENCH_DATA, Func.sha2_512)
   
   @pytest.mark.benchmark
   def test_bench_sum_blake3(benchmark):
       benchmark(sum, BENCH_DATA, Func.blake3)
   
   @pytest.mark.benchmark
   @pytest.mark.parametrize("bits", [8, 128, 256, 384, 512])
   def test_bench_sum_blake2b(benchmark, bits):
       func = getattr(Func, f"blake2b_{bits}")
       benchmark(sum, BENCH_DATA, func)
   
   @pytest.mark.benchmark
   def test_bench_encode(benchmark):
       digest = sum(BENCH_DATA, Func.sha2_256)
       benchmark(digest.encode)
   
   @pytest.mark.benchmark
   def test_bench_decode(benchmark):
       encoded = sum(BENCH_DATA, Func.sha2_256).encode()
       benchmark(decode, encoded)
   

Related

• Go benchmarks: go-multihash sum_test.go, multihash_test.go

Add pytest-benchmark as a development dependency, then create tests/test_benchmarks.py with the benchmark cases and parameters shown in the issue. Start by checking the existing test and dependency setup, then run the benchmark-marked tests. Done means sum(), encode(), decode(), and the listed hash variants have repeatable benchmark coverage.