Add Python integration tests for quantum circuit API

[tianyan-admin]

Summary

The cqlib Python bindings (binding-python) have a core test suite in tests/python/, but some circuit API methods lack dedicated test coverage. This issue is to add integration tests for circuit construction and manipulation APIs.

What to do

Add Python tests in tests/python/ covering the following circuit operations:

1. Basic gate operations

   • Test Circuit.h(), Circuit.cx(), Circuit.x(), Circuit.y(), Circuit.z()
   • Verify num_qubits and operation count

2. Parameterized circuits

   • Test Circuit.rx(), Circuit.ry(), Circuit.rz() with Parameter
   • Test assign_parameters() with various parameter values

3. Edge cases

   • Empty circuit (zero qubits)
   • Large circuits (e.g., 100+ qubits)
   • Invalid qubit indices

Skills needed

• Basic Python programming
• Basic understanding of quantum circuits
• Experience with pytest is a plus

Getting started

git clone https://github.com/cq-lib/cqlib.git
cd cqlib

# Set up Python environment
python3 -m venv .venv
source .venv/bin/activate
pip install maturin pytest

# Build Python bindings
maturin develop -m crates/binding-python/Cargo.toml

# Run existing tests
pytest tests/python/ -v

# Add your tests in tests/python/ and run them
pytest tests/python/ -v

Example test

# tests/python/test_circuit_basics.py
from cqlib import Circuit

def test_bell_state():
    """Test basic Bell state construction"""
    qc = Circuit(2)
    qc.h(0)
    qc.cx(0, 1)

    assert qc.num_qubits == 2
    assert len(qc.operations) == 2

Acceptance criteria

• Tests for at least 3 different gate types
• Tests for parameterized circuits with assign_parameters()
• At least one edge-case test
• All tests pass with pytest tests/python/ -v
• Code passes ruff check

Related

• [CONTRIBUTING.md](https://github.com/cq-lib/cqlib/blob/main/CONTRIBUTING.md) - Development setup guide
• [README.md](https://github.com/cq-lib/cqlib#readme) - Circuit API examples
• [Python tests directory](https://github.com/cq-lib/cqlib/tree/main/tests/python)