test: add conftest.py with shared fixtures and pytest.ini config

- Add conftest.py with reusable fixtures (test_data_dir, cfdi_ejemplos_dir,
  csd_dir, sample_cfdi_v40, sample_cfdi_v33, tmp_output_dir)
- Register custom markers (slow, network, pac, render, create)
- Add pytest.ini with testpaths and default options

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: satcfdi

pytest.ini

@@ -0,0 +1,5 @@
+[pytest]
+testpaths = tests
+python_files = test_*.py
+python_functions = test_*
+addopts = -v --tb=short

tests/conftest.py

@@ -0,0 +1,63 @@
+"""Shared pytest configuration and fixtures for satcfdi tests."""
+
+import os
+import logging
+
+import pytest
+
+from satcfdi.cfdi import CFDI
+from satcfdi.models import Signer
+
+
+TESTS_DIR = os.path.dirname(__file__)
+
+
+@pytest.fixture(scope="session")
+def test_data_dir():
+    """Return the path to the tests directory containing test data."""
+    return TESTS_DIR
+
+
+@pytest.fixture(scope="session")
+def cfdi_ejemplos_dir():
+    """Return the path to the CFDI examples directory."""
+    return os.path.join(TESTS_DIR, "cfdi_ejemplos")
+
+
+@pytest.fixture(scope="session")
+def csd_dir():
+    """Return the path to the CSD certificates directory."""
+    return os.path.join(TESTS_DIR, "csd")
+
+
+@pytest.fixture
+def sample_cfdi_v40(cfdi_ejemplos_dir):
+    """Load a sample CFDI v4.0 for testing."""
+    return CFDI.from_file(
+        os.path.join(cfdi_ejemplos_dir, "comprobante40", "cfdv40-ejemplo.xml")
+    )
+
+
+@pytest.fixture
+def sample_cfdi_v33(cfdi_ejemplos_dir):
+    """Load a sample CFDI v3.3 for testing."""
+    return CFDI.from_file(
+        os.path.join(cfdi_ejemplos_dir, "comprobante33", "cfdv33-ejemplo.xml")
+    )
+
+
+@pytest.fixture
+def tmp_output_dir(tmp_path):
+    """Provide a temporary directory for test output files."""
+    output = tmp_path / "output"
+    output.mkdir()
+    return output
+
+
+def pytest_configure(config):
+    """Register custom markers."""
+    config.addinivalue_line("markers", "slow: marks tests as slow (deselect with '-m \"not slow\"')")
+    config.addinivalue_line("markers", "network: marks tests that require network access")
+    config.addinivalue_line("markers", "pac: marks tests that interact with PAC providers")
+    config.addinivalue_line("markers", "render: marks tests for PDF/HTML rendering")
+    config.addinivalue_line("markers", "create: marks tests for CFDI creation")